Impact of delivery system type on curcumin bioaccessibility

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Food and Beverage Chemistry/Biochemistry

Impact of delivery system type on curcumin bioaccessibility: Comparison of curcumin-loaded nanoemulsions with commercial curcumin supplements Bingjing Zheng, Shengfeng Pen, Xiaoyun Zhang, and David Julian McClements J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b03174 • Publication Date (Web): 25 Sep 2018 Downloaded from http://pubs.acs.org on September 26, 2018

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Journal of Agricultural and Food Chemistry

ACS Paragon Plus Environment


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Impact of delivery system type on curcumin bioaccessibility: Comparison of

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curcumin-loaded nanoemulsions with commercial curcumin supplements

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Bingjing Zhenga, Shengfeng Pengab, Xiaoyun Zhanga, and David Julian McClementsa

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a

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Massachusetts Amherst, Massachusetts 01003, United States

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b

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330047 Jiangxi, P.R. China

Biopolymers and Colloids Laboratory, Department of Food Science, University of State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang,

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Corresponding author:

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David Julian McClements, E-mail address: [email protected]; Telephone: +1413

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545 2275

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ABSTRACT In this study, nanoemulsion-based delivery systems fabricated using three different methods

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were compared with three commercially available curcumin supplements. Powdered curcumin

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was dispersed into the oil-in-water nanoemulsions using three methods: the conventional oil-

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loading method; the heat-driven method; and, the pH-driven method. The conventional method

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involved dissolving powdered curcumin in the oil phase (60 oC, 2 h) and then forming a

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nanoemulsion. The heat-driven method involved forming a nanoemulsion and then adding

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powdered curcumin and incubating at an elevated temperature (100 oC, 15 min). The pH-driven

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method involved dissolving curcumin in an alkaline solution (pH 12.5) and then adding this

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solution to an acidified nanoemulsion (pH 6.0). The three commercial curcumin products were

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capsules or tablets purchased from an online supplier: Nature Made, Full Spectrum, and

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CurcuWin. Initially, the encapsulation efficiency of the curcumin in the three nanoemulsions was

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determined and decreased in the following order: pH-driven (93%) > heat-driven (76%) >

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conventional (56%) method. The different curcumin formulations were then subjected to a

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simulated gastrointestinal tract (GIT) model consisting of mouth, stomach, and small intestine

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phases. All three nanoemulsions had fairly similar curcumin bioaccessibility values (74-79%)

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but the absolute amount of curcumin in the mixed micelle phase was highest for the pH-driven

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method. A comparison of these nanoemulsions and commercial products indicated that the

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curcumin concentration in the mixed micelles decreased in the following order: CurcuWin ≈ pH-

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driven method > heat-driven method > conventional method >> Full spectrum > Nature Made.

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This study provides valuable information about the impact of the delivery system type on

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curcumin bioavailability. It suggests that encapsulating curcumin within small lipid particles

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may be advantageous for improving its absorption form the GIT.

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Keywords: curcumin; emulsion; nanoemulsion; supplements; pH-driven method; nutraceuticals;

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bioaccessibility

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INTRODUCTION

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Curcumin, a bioactive constituent found in turmeric, has anti-oxidative and anti-

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inflammatory properties that have led to its application as a nutraceutical or pharmaceutical to

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inhibit or treat certain diseases, such as rheumatoid arthritis, cystic fibrosis, inflammatory bowel

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disease, and colon cancer 1-3. In foods, curcumin is also used as a natural pigment because it has

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a desirable yellow-orange color. Curcumin has a relatively low toxicity and is generally

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regarded as safe (GRAS) by the United States Food and Drug Administration (FDA). The

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potentially beneficial biological activities exhibited by curcumin has led the pharmaceutical,

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supplement, and food industries to develop forms suitable for oral ingestion, such as pills,

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capsules, powders, foods, and drinks 4-7. However, there are a number of hurdles that have to be

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overcome before curcumin can be utilized in these products, including its crystalline nature, low

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water-solubility, alkaline degradation, and low oral bioavailability 8.

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The oral bioavailability and bioactivity of curcumin depends on the physical form it is

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delivered in. A number of studies have reported that encapsulation of curcumin within colloidal

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particles enhances its bioavailability 7-12. Many of the conventional technologies used to

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incorporate curcumin into colloid dispersions utilize either heating or organic solvents, which

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both have technical challenges 6, 13, 14. The main disadvantage of heating is that curcumin

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chemically degrades at high temperatures, which leads to a loss of its biological activity 6, 7, 9, 15,

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costly 17, 18. Consequently, there is interest in developing alternative approaches to incorporate

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curcumin into colloidal delivery systems.

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. The main disadvantage of organic solvents is that they are environmentally unfriendly and

Recently, a novel pH-driven method has been developed to incorporate hydrophobic

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molecules, such as curcumin, into colloid delivery systems without using elevated temperatures

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or organic solvents 19-22. This method is based on the fact that the water-solubility of curcumin is

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highly dependent on pH. Curcumin is practically insoluble in water under acidic and neutral

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conditions, but highly soluble under alkaline conditions because it is a weak Brønsted acid with

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three labile protons at high pH values: pKa = 7.5, 8.5, and 9.5 6, 23, 24. Consequently, the water-

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solubility of curcumin increases when the pH increases above neutral because the molecules

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becomes progressively more negatively charged. Conversely, when the pH of an alkaline

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curcumin solution is reduced, the negative charge on the curcumin is reduced and it becomes

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insoluble. The pH-driven method utilizes this phenomenon to load curcumin into oil-in-water


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emulsions. The curcumin is first dissolved in an alkaline solution, which is then mixed with an

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acidified emulsion. When the pH of the entire system decreases, the curcumin becomes

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insoluble and is driven into the interior of the oil droplets.

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The main objective of the current study was to compare the pH-driven method of loading

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nanoemulsions with curcumin with two more commonly used methods: the conventional method

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and the heat-driven method. The conventional method involved dissolving powdered curcumin

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in an oil phase and then blending this with an aqueous phase to form a curcumin-loaded

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nanoemulsion. The heat-driven method involved forming a nanoemulsion first, then adding

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powdered curcumin, and then incubating the mixed system at an elevated temperature to cause

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the curcumin crystals to dissolve and move into the oil droplets. The encapsulation efficiency

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and bioaccessibility of curcumin in nanoemulsions prepared using the three different loading

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methods was compared. In addition, the efficacy of the nanoemulsion-based delivery systems

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prepared in this study were compared to those of three commercial formulations in terms of their

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ability to increase curcumin bioaccessibility. Due to the increasing trend towards clean-labels in

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the food industry, all-natural ingredients were utilized to fabricate the curcumin-loaded

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nanoemulsions. The results of this study should have important implications for the design and

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formulation of more efficacious nutraceutical delivery systems.

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MATERIAL & METHODS

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Materials

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Corn oil was purchased from a local supermarket and used without further purification

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(Mazola, ACH Foods, Cordova, TN). Curcumin supplements produced by Nature Made (Nature

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Made Nutritional Products, Mission Hills, CA), Full Spectrum (Solgar, Inc., Leonia, NJ), and

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CurcuWin (Relentless Improvement® LLC, Reno, NV) were also purchased from an on-line

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supplier (Amazon.com). The main components within each of these supplements are described in

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the results and discussion section. The following chemicals were purchased from the Sigma-

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Aldrich Chemical Company (St. Louis, MO): curcumin (C1386-10G, purity ³65%); mucin from

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porcine stomach (M2378-100G); pepsin from porcine gastric mucosa (P7000-25G); lipase from

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porcine gastric mucosa (L3126-100G); porcine bile extract (B8831-100G); sodium hydroxide

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(SS266-4L), and Nile Red (N3013-100MG). Quillaja saponin (Q-Naturale® 200) was provided

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by Ingredion Inc. (Westchester, IL).


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The three commercial curcumin supplements had different physical forms. The Nature

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Made (NM) and CurcuWin (Win) products were powders, whereas the Full Spectrum (FS)

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products was a liquid. The NM product appeared to be prepared by directly adding powdered

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curcumin into capsules with other inactive ingredients. However, the Win product appeared to

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be prepared using a patented technology (UltraSol®) from Omniactive Healthy Technologies

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(Canada), which involves incorporating curcumin into food-grade nanoparticles with

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antioxidants. The FS product was a water-soluble form containing curcumin stabilized by a

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synthetic surfactant (Polysorbate 80).

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Preparation protocol

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The curcumin nanoemulsions were prepared using three different approaches: the

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conventional method; heat-driven method; and, pH-driven method.

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Conventional method

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Curcumin-loaded nanoemulsions were produced using the conventional method by

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dispersing powdered curcumin into an oil phase (corn oil) prior to homogenization. A weighed

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amount of curcumin powder was added to the oil phase (3 mg/g) and then the mixture was

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incubated at 60 °C for 2 hours to ensure fully dissolution. The aqueous phase was prepared by

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mixing Quillaja saponin (2% w/w) with phosphate buffer solution (10 mM, pH 6) for 5 min. A

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coarse emulsion was then formed by blending 10% (w/w) of curcumin-loaded oil with 90%

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(w/w) of aqueous phase for 2 min using a high-speed blender (M122.1281-0, Biospec Products,

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Inc., ESGC, Switzerland). A nanoemulsion was then formed by passing the coarse emulsion five

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times through a high-pressure homogenizer (Microfluidizer M-110Y, Microfluidics, Newton,

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MA USA) with a 75-µm interaction chamber (F20Y) at an operating pressure of 12,000 psi (83

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MPa). The resulting curcumin nanoemulsion was stored at 4 °C in the dark before being used.

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The nanoemulsions were then diluted 1:1 (w/w) using double distilled water so that the final

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system contained 0.15 mg curcumin per g emulsion for the in vitro studies.

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Heat-driven method

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Curcumin-loaded nanoemulsions were prepared using the heat-driven method by mixing

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powdered curcumin with heated nanoemulsions. The stock nanoemulsions were fabricated by

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homogenizing 10% (w/w) oil phase (corn oil) and 90% (w/w) aqueous phase (2 % w/w Q-


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naturale, 10 mM phosphate buffer, pH 6) using the same approach as described for the

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conventional method. Powdered curcumin (0.3 mg/g) was then added to the stock nanoemulsion

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and the resulting mixture was incubated at 100 °C for 15 min in the dark with constant stirring.

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This system was then diluted 1:1 (w/w) with double distilled water to obtain a final system

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containing 5% oil and 0.15 mg curcumin /g emulsion.

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pH-driven method

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The curcumin-loaded nanoemulsions fabricated using the pH-driven method were prepared

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by mixing an alkaline solution of dissolved curcumin with a stock nanoemulsion, which was

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slightly acidic (pH 6). An alkaline curcumin solution (6 mg/g, pH 12.5) was prepared by adding

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powdered curcumin into an alkaline solution (0.1N sodium hydroxide) and then stirring for 2

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min in the dark at ambient temperature. The alkaline curcumin solution was then added to a

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stock nanoemulsion (prepared using the same method as for the heat-driven method) to reach a

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final concentration of 0.3 mg curcumin per g emulsion. The mixed nanoemulsion formed has

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immediately adjusted back to pH 6 and then stirred for 30 min in the dark at ambient

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temperature. Again, the samples were diluted with double distilled water to obtain a final system

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containing 5% oil and 0.15 mg curcumin per g emulsion.

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Commercial curcumin supplements

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Initially, the curcumin concentration of each product was determined based on a standard

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curve prepared using pure curcumin. The curcumin was extracted from each sample using

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chloroform. The samples were diluted with double distilled water to obtain final systems

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containing 0.15 mg of curcumin per g sample.

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Optical properties

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The optical properties of curcumin dispersions prepared using different fabrication methods

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was characterized by measuring their color coordinates. An instrumental colorimeter (ColorFlex

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EZ 45/0-LAV, Hunter Associates Laboratory Inc., Virginia, USA) was used to determine the

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color coordinates: L* (lightness/darkness); a* (redness/greenness); and b* (yellowness/blueness).

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An aliquot of sample (10 mL) was placed in a Petri dish, and then illuminated using D65-

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artificial daylight (10° standard angle) with a black background. Three replicate measurements

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were taken and averaged to represent the final results. Only the b* and L* values are reported

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here because they best represent the yellow color and lightness of the curcumin-loaded systems.


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Simulated gastrointestinal digestion A gastrointestinal tract (GIT) model was used to analyze the effect of delivery system type

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on the potential gastrointestinal fate of curcumin. The model mimicked the mouth, stomach, and

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small intestine stages of the GIT and is based on a previously described model developed in our

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laboratory 25. An equal amount of each sample (30 mL) was transferred into a glass beaker and

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then incubated at 37 °C in a shaking incubator (Innova Incubator Shaker, Model 4080, New

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Brunswick Scientific, New Jersey, USA). Each sample contained 0.15 mg curcumin per g

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sample, while all the emulsions containing the same level of oil (5% w/w).

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Oral phase

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An artificial saliva stock solution (ASSS) was prepared and used within 2 days of the study.

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The ASSS was fabricated by mixing sodium chloride (1.594 g/L), ammonium nitrate (0.328

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g/L), potassium phosphate (0.636 g/L), potassium chloride (0.202 g/L), potassium citrate (0.308

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g/L), uric acid sodium salt (0.021 g/L), urea (0.198 g/L), lactic acid sodium salt (0.146 g/L) with

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double distilled water (1 L) and storing at 4°C overnight. Then, a stock simulated saliva fluid

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(SSF) was prepared by adding 90 mg mucin into 30 g ASSS and stirred overnight at 4 °C before

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the digestion study.

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For the oral phase study, the initial sample (30 mL) and SSF (30 mL) were heated to 37 °C

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for 10 min prior to starting. The two samples were then transferred into a glass beaker after

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incubation and the pH was adjusted to 6.8. The resulting mixture was then placed into a shaking

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incubator operating at 100 rpm and 37 °C for 2 min to mimic oral conditions.

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Stomach phase

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Initially, a simulated gastric fluid work solution (SGFWS) was prepared by adding pepsin

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(3.2 mg/g) into stimulated gastric fluid (SGF) and then stirring for 40 min at room temperature.

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The SGF was produced by fully dissolving sodium chloride (2 g/L) and hydrochloric acid (83.3

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mM/L or 7 mL/L) into double distilled water at room temperature. The remaining SGF solution

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was placed into the refrigerator (4°C) before experiments. The sample and SGF were preheated

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to 37 °C for 10 min before each study. Samples (40 g) collected from the mouth phase were

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mixed with SGF (40 g) and then adjusted to pH 2.5. The samples were then continuously

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agitated for 2 hours using an incubator shaker set at 100 rpm and 37 °C.

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Small Intestine phase


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Initially, three solutions containing intestinal constituents were prepared and incubated in a

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water bath (37°C): stock simulated intestinal fluids (SIF); bile salt solution; and, lipase solution.

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The stock SIF was prepared by fully dissolving calcium chloride (5.5 g) and sodium chloride

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(32.87 g) in 150 ml double distilled water. The bile salt solution was prepared by mixing porcine

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bile extract (53.57 mg/mL) with phosphate buffer (5 mM, pH 7) overnight at room temperature

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with continuous stirring. The lipase solution (24 mg/ mL) was prepared 30 min before utilization

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by mixing powdered lipase with phosphate buffer (5 mM, pH 7).

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Samples collected from the stomach phase (60 g) were transferred into a water bath at a

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temperature of 37 °C. An automatic titration unit (Metrohm, USA Inc.) was used to monitor and

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maintain a neutral pH in the sample. First, the sample was adjusted to pH 7, subsequently, 3 mL

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SIF containing (0.5 M CaCl2 and 7.5 M NaCl) and 7 mL bile salt solution (containing 375 mg

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bile extract) was added to the sample, which was then adjusted back to pH 7. Finally, 5 mL of

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lipase solution (containing 120 mg lipase) was added to this mixture and the automatic titration

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device was started. The volume of alkaline solution (0.25 M NaOH solution) required to

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maintain a neutral pH was recorded throughout the digestion period. All solutions were

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preheated to 37 oC for 5 min before being used.

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The amount of NaOH solution required to neutralize the free fatty acids (FFA) released was recorded and used to estimate the fraction of FFA released 25: 𝐹𝐹𝐴(%) = 100 ×

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𝑉,-./ 𝑚,-./ 𝑀23435 2 W238935

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Here, FFA (%) is the percentage of released FFAs; VNaOH is the volume of titrant required to

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neutralize the FFA; mNaOH is the molarity of sodium hydroxide; Mlipid is the molecular weight of

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the oil used (gram per mole); and the “2” represents the fact that two FFAs are released from a

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triglyceride, and Wlipid is the mass (gram) of the oil in the digestion system.

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Particle characterization

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A laser light scattering instrument (Mastersizer 2000, Malvern Instruments Ltd., Malvern,

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Worcestershire, U.K.) was used to measure the particle diameter and particle size distribution of

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the samples. A particle electrophoresis device (Zetasizer Nano, Malvern Instruments, Worcester-

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shire, U.K.) was used to determine the ζ-potential values of the particles. The initial, mouth and

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small intestine samples were diluted with phosphate buffer (5 mM, pH 7), while the stomach


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samples were adjusted with acidified double distilled water (pH 2.5) to avoid multiple scattering

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effects.

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Microstructure analysis

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A confocal scanning laser microscope (Nikon D-Eclipse C1 80i, Nikon, Melville, NY) was

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used to characterized the microstructure of the samples with a 200´ magnification (20´ objective

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lens 10´ eyepiece). The oil regions in the samples were stained by adding a hydrophobic

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fluorescence dye in the form of Nile red solution (1 mg/mL ethanol).

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Curcumin concentration determination

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The level of curcumin in the initial samples, mixed micelle fraction, and total digest fraction

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were measured. The curcumin concentration in the samples was quantified using an UV-visible

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spectrophotometer at a wavelength of 419 nm (Cary 100 UV−vis, Agilent Technologies, Santa

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Clara, CA, USA). Samples were collected after the small intestine phase and split into two

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portions: the mixed micelle fraction and the total digest fraction. The mixed micelle fraction was

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transferred into a centrifuge tube and centrifuged (18,000 rpm, 25 °C) for 50 min (Thermo

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Scientific, Waltham, MA). The clear top layer of these samples was collected to represent the

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“mixed micelle fraction” where the curcumin was solubilized. The total digest fraction was used

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directly without any centrifugation. The concentration of curcumin in each fraction was

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determined by adding chloroform and then centrifuging at 3000 rpm for 10 min. The

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hydrophobic curcumin moved into the chloroform layer. The concentration of the curcumin in

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the separated chloroform layers was then determined using a standard curve prepared by

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measuring the absorbance of known curcumin samples (Supplementary information Fig. 1).

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The encapsulation efficiency of the curcumin, which represents the percentage of curcumin encapsulated inside the lipid droplets, was calculated using the following equation: 𝐸𝑛𝑐𝑎𝑝𝑠𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 (%) = 100 ×

𝐶3I3J3-2 𝐶 KL4KMJK5

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The bioaccessibility of curcumin, which is the fraction in the small intestine that was

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solubilized in the mixed micelle phase (and therefore potentially available for absorption), was

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calculated using the following equation:

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𝐵𝑖𝑜𝑎𝑐𝑐𝑒𝑠𝑠𝑖𝑏𝑖𝑙𝑖𝑡𝑦 (%) = 100 ×

𝐶P3MK22K 𝐶53QKRJ


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The stability of curcumin, which is the fraction remaining in the original state in the small intestine phase, was calculated using the following equation: 𝑆𝑡𝑎𝑏𝑖𝑙𝑖𝑡𝑦(%) = 100 ×

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𝐶53QKRJ 𝐶3I3J3-2

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Here, Cexpected is the original amount of curcumin used to formulate the systems; Cinitial is the

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measured curcumin concentration in the initial sample, Cmicelle is the concentration of curcumin

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in the mixed micelle faction; and, Cdigest is the concentration of curcumin in the total digest.

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Statistical analysis

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All experiments were performed on at least three freshly prepared samples. The resulting

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data are measured as the mean ± standard deviation calculated from this data. Statistical

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differences among samples were determined using statistical analysis software (SPSS, IBM

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Corporation, Armonk, NY, USA), with p< 0.05 being considered as a significant difference.

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RESULTS & DISCUSSION

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Influence of curcumin loading method

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Initially, the impact of the three different loading methods on the formation and properties of

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the curcumin-loaded nanoemulsions was investigated: the conventional; heat-driven; and, pH-

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driven.

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Influence of loading method on encapsulation efficiency

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An equal amount of curcumin powder (150 µg/mL) was used to prepare each nanoemulsion.

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However, the total amount of curcumin encapsulated within the nanoemulsions after fabrication

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was different: 140 µg/mL for the pH-driven method; 114 µg/mL for the heat-driven method; and,

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83 µg/mL for the conventional method (Table 1). Consequently, the encapsulation efficiency of

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the pH-driven method (93%) was considerably higher than that of the heat-driven (76%) or

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conventional (56%) methods. There are a number of potential reasons for these differences.

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First, the pH-driven method is carried out at ambient temperature and so there is little thermal

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degradation of the curcumin. In contrast, both the heat-driven (100 °C for 15 min) and

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conventional (60°C for 2 h) methods required a thermal processing step that could damage the

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curcumin. The fact that the amount of curcumin was lower in the nanoemulsions prepared using

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the conventional method suggests that the prolonged heating time used caused more extensive


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thermal degradation. Second, the different loading methods may have resulted in different

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amounts of curcumin crystallization during the nanoemulsion preparation procedure. Previous

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studies have shown that curcumin dissolved at high temperatures may crystallize when the

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system is cooled 13, 26. In our study, we observed an orange precipitate at the bottom of the

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nanoemulsions prepared using the conventional method, which was presumably due to the

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formation and sedimentation of curcumin crystals (Fig. 1). In contrast, no orange precipitate was

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observed for the heat-driven and pH-driven methods, which suggests that loading the curcumin

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after the nanoemulsions have been formed inhibited crystallization, possibly because the lipid

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particles always had small dimensions. The solubility of substances is known to increase as the

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size of the particles they are contained within decreases due to a thermodynamic effect related to

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increased specific surface area 27.

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The colorimetry measurements of the nanoemulsions supported the loading measurements.

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All samples had positive b-values and high L-values corresponding to materials with a yellowish

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color and strong lightness. As expected, the intensity of the yellow color of the nanoemulsions

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decreased with decreasing encapsulation efficiency: b* = 93, 87, and 73 for the pH-driven, heat-

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driven, and conventional methods, respectively.

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Influence of loading method on gastrointestinal fate of curcumin nanoemulsions

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The impact of loading method on the gastrointestinal fate of the curcumin-loaded

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nanoemulsions was monitored using a simulated GIT. The particle size distribution (Fig. 2),

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mean particle diameter (Fig. 3), microstructure (Fig. 4) and z-potential (Fig. 5) of samples

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collected from nanoemulsions exposed to mouth, stomach and intestinal phase were fairly

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similar to each other. This similarity can be attributed to the fact that all the nanoemulsions

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initially contained similar particle sizes, compositions, and charges.

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Initial: Initially, the particle size distributions (PSDs) of the curcumin-loaded nanoemulsions

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was monomodal and the mean particle diameters were relatively small (d32 < 200 nm) (Figures 2

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and 3). The confocal microscopy images indicated that the lipid droplets were evenly distributed

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throughout the samples, indicating they were stable to flocculation. Interestingly, the light

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scattering data and the microscopy images indicated that the nanoemulsions prepared using the

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heat-driven method contained slightly larger droplets than the other two systems. This may have

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been because these nanoemulsions were held at a high temperature during their preparation,

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which may have caused some droplet aggregation. Indeed, previous studies have shown that


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lipid droplets coated with quillaja saponins undergo some aggregation at elevated temperatures

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. All the curcumin-loaded lipid droplets initially had a relatively high negative surface

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potential (ζ > -40 mV) (Table 1), which can be attributed to the presence of carboxylic acid

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groups that have pKa values around pH 3.5 28, 29. This relatively high surface potential is

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important for nanoemulsion stability because it generates a strong electrostatic repulsion between

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the lipids particles 30. The fact that all the samples had similar surface potentials suggests that

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the interfacial composition was not highly dependent on the curcumin-loading method used.

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Oral phase: The PSDs of all the nanoemulsions were still monomodal after exposure to

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simulated oral conditions, but the mean particle diameter increased compared to the initial

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samples (Figs. 2 and 3). Moreover, the confocal microscopy images indicated that there were

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some larger particles in the samples (Fig. 4), which is indicative of droplet aggregation. The

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magnitude of the surface potential on the particles in the samples changed from around -40 mV

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to around -30 mV after exposure to the simulated saliva. These effects can be attributed to the

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presence of mineral ions and mucin molecules in the saliva. The mineral ions screen the

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electrostatic repulsion between the lipid particles while the mucin molecules can promote

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depletion and/or bridging flocculation 31-33.

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Stomach phase: The PSDs became bimodal after exposure to the stomach phase with a

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population of relatively small particles and another population of relatively large particles (Fig.

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2). As expected, this led to an increase in the mean particle diameter of the samples compared to

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the mouth phase (Fig. 3). The confocal microscopy images indicated that many of the lipid

345

droplets in these samples were clustered together (Fig. 4). Taken together, these results are

346

characteristic of the lipid droplet aggregation that is often observed under simulated gastric

347

conditions 31, 34. The surface potentials of the particles became slightly positive (≈ +1 mV) after

348

exposure to the stomach phase due to the relatively low pH and high ionic strength of the

349

simulated gastric fluids (Fig. 5). Specifically, the low pH leads to protonation of the carboxylic

350

acid groups on the adsorbed surfactant molecules while the mineral ions cause electrostatic

351

screening 7, 34.

352

Small intestine phase: The PSDs of all the samples were relatively broad after exposure to

353

the simulated small intestinal phase (Fig. 2), which reflects the fact that there are many kinds of

354

colloidal particles present after digestion, including micelles, vesicles, calcium-fatty acid soaps,


12


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355

and undigested lipid droplets 35. The mean particle diameter of the samples in the small intestine

356

phase was fairly similar to that in the stomach phase (Fig. 3) but does not reflect the broad range

357

of particle sizes present. The confocal microscopy images indicated that most of the lipid

358

droplets had been digested, but that there were some relatively large lipid-rich particles present.

359

The surface potential of the particles was negative (-20 mV) due to the fact that most of the

360

constituents making up the colloidal particles in the neutral intestinal fluids are anionic, such as

361

bile acids, free fatty acids, saponins, and peptides.

362

Influence of loading method on lipid digestion profile

363

In this section, the impact of the curcumin loading method on the lipid digestion profiles of

364

the nanoemulsions was investigated using an automatic titration unit. The volume of sodium

365

hydroxide (NaOH) solution required to maintain neutral pH in the samples when they were

366

exposed to simulated small intestinal conditions was monitored. This volume was then used to

367

calculate the fraction of FFAs released. Overall, the FFA release profiles of the three

368

nanoemulsions were very similar (Fig. 6). The amount of FFAs released increased rapidly during

369

the first 10 min and then gradually increased for the remainder of the digestion period. These

370

results are consistent with previous studies that have also reported that the small lipid droplets in

371

nanoemulsions are rapidly digested by lipase because of their high surface area 7, 36, 37. Overall,

372

these results indicate that the curcumin loading method used to prepare the nanoemulsions did

373

not have a major impact on lipid digestion.

374

Influence of loading method on physiochemical characteristics of mixed micelles

375

The impact of the curcumin loading method on the properties of the mixed micelles formed

376

at the end of the small intestine phase was also investigated. Initially, the raw digest was

377

centrifuged to remove any large particles such as insoluble calcium-fatty acid soaps and

378

undigested lipid droplets. The size and electrical characteristics of the particles remaining in the

379

clear mixed micelle phase were then measured. The mean particle diameter of the mixed

380

micelles collected from all three curcumin nanoemulsions was fairly similar: d32 = 146 ± 2 nm,

381

136 ± 2 nm and 158 ± 2 nm for the conventional, heat-driven, and pH-driven methods,

382

respectively. Similarly, the surface potentials of the mixed micelles from each sample were also

383

relatively similar: ζ-potential = -21 ± 3 mV, -26 ± 3 mV and -21 ± 2 mV, respectively. The

384

negative charges on the mixed micelles can be attributed to the fact that they were mainly

385

comprised of neutral (monoacylglycerols) and anionic (bile salts and free fatty acids) molecular


13

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386

species 7, 35. These results suggest that the loading method did not have a major impact on the

387

nature of the mixed micelles formed after digestion.

388

Influence of loading method on curcumin bioaccessibility and stability

389

After the small intestinal phase, the curcumin concentration in the raw digest and mixed

390

micelle phases were measured to determine the impact of loading method on the bioaccessibility

391

and stability of the curcumin in the nanoemulsions. The level of curcumin in the raw digest

392

represents the amount of curcumin remaining in the small intestine after digestion, i.e., the

393

fraction that has passed through the mouth, stomach, and small intestine without chemically

394

degrading. The concentration of curcumin in the mixed micelle phase represents the curcumin

395

molecules that were chemically stable and solubilized within the mixed micelles. The amount of

396

curcumin in the mixed micelle phase and in the raw digest were affected by the loading method

397

used: pH-driven > heat-driven > conventional method (Fig. 7a). This effect can be attributed to

398

differences in the initial encapsulation efficiency of the three nanoemulsions, which decreased in

399

the same order (Table 1). As would be expected, a higher level of curcumin in the initial

400

nanoemulsions led to a higher level of curcumin in the small intestine. These results suggest that

401

the pH-driven method is the most effective at delivering a higher absolute amount of curcumin to

402

the small intestine. However, when the curcumin concentrations are normalized to the total

403

amount of curcumin in the digest, then the overall bioaccessibility was relatively independent of

404

the loading method used (Fig. 7b). This would also be expected because there would have been

405

proportionally higher levels of curcumin in both the mixed micelles and digest.

406

Another important factor that impacts the overall bioavailability of curcumin is its stability

407

to degradation within the gastrointestinal tract. The fraction of curcumin that remained after the

408

small intestine phase was therefore determined relative to the initial amount in each system (Fig.

409

7b). The fraction of curcumin remaining decreased in the following order: conventional > heat-

410

driven > pH-driven method. This suggests that the curcumin was more stable in the

411

nanoemulsions prepared using the conventional method than those prepared using the pH-driven

412

method. The effect may have occurred because some of the curcumin was in a crystalline form

413

in the nanoemulsion prepared using the conventional method and was therefore more resistant to

414

chemical degradation by aqueous phase components. Even so, the curcumin was relatively

415

stable in all three systems, with > 80% remaining by the end of digestion. It should be noted that

416

our in vitro GIT model did not include the Phase I and Phase II metabolic enzymes that are


14


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417

present in the human gastrointestinal tract, which means that changes in curcumin due to

418

metabolism were not accounted for. Curcumin is known to undergo considerable metabolism in

419

the GIT and therefore future studies should take this phenomenon into account 38.

420

Gastrointestinal fate of commercial curcumin supplements

421

Curcumin supplements are already commercially available and are sold in many

422

supermarkets, pharmacies, health food shops, and on-line retailers. These supplements come in a

423

variety of physical forms, including capsules, pills, fluids, and powders. The precise physical

424

form of the curcumin within a supplement has a major impact on its bioaccessibility and

425

stability. For this reason, we measured the gastrointestinal fate of three curcumin supplements

426

purchased from an on-line supplier: Nature Made (NM), Full Spectrum (FS) and Curcuwin

427

(Win). The curcumin supplements from NM and Win were in a powdered form, whereas the one

428

from FS was in a liquid form (contained inside capsules). The commercial curcumin samples

429

were removed from their capsules prior to testing and the capsules themselves were not used

430

because they would interfere with the subsequent analysis.

431

Initial characteristics of curcumin supplements

432

Initially, the general properties of the three curcumin supplements used were established

433

based on information reported on the manufacturers label and visual observations. The active

434

ingredient in the NM supplement were reported to be a turmeric blend containing curcuminoids

435

(47.5 mg), while the inactive ingredients were cellulose gel, gelatin, water, stearic acid,

436

magnesium stearate, and silicon dioxide (in descending weight). These inactive ingredients have

437

been reported to have a variety of functions in supplements, including acting as lubricants,

438

suspending agents, stabilizers, and flow enhancers 39-42. In addition, other functions have been

439

reported for specific types of these inactive ingredients. Cellulose prolongs the shelf life of

440

supplements by protecting powdered curcumin from oxygen, humidity, and enzymatic

441

degradation 42. Stearic acid and magnesium stearate act as emulsifying and solubilizing agents

442

that can improve the water-dispersion and oral bioavailability of hydrophobic substances 40.

443

The active ingredient in the fluid FS supplement was reported to be curcuminoids, while the

444

inactive ingredients were polysorbate 80, gelatin, and vegetable glycerin. Polysorbate 80, also

445

known as Tween 80, is a synthetic non-ionic surfactant that can improve the water-dispersibility

446

of curcumin by spontaneously forming nanoemulsions or microemulsions in aqueous


15

Page 17 of 36


447

gastrointestinal fluids 43. Gelatin is a gel-forming protein used to form soft gel capsules that

448

protect curcumin during storage and within the mouth, but then dissociate and release it within

449

the stomach 44. Glycerin acts as a cosolvent that facilitates the spontaneous formation of

450

microemulsions and emulsions in gastrointestinal fluids 45. The active ingredient in the Win supplement was reported to be curcuminoids, while the

451 452

inactive ingredients were reported to be polyvinylpyrrolidone (PVP), cellulose, and mixed

453

tocopherols. PVP is a synthetic water-soluble amphiphilic polymer that increases the water-

454

dispersibility of curcumin by encapsulating it within small colloidal particles 46-48. Cellulose

455

functions as a stabilizer and lubricant that enhances bioactive stability and powder flowability 41,

456

42

457

ingredients such as curcumin 49.

458

Digestibility on curcumin supplements

459

. Mixed tocopherols are a natural antioxidant that inhibit the chemical degradation of active

Each commercial curcumin formulation was passed through the same simulated GIT used to

460

test the nanoemulsions and then the concentrations of curcumin in the mixed micelles and raw

461

digest were measured. The bioaccessibility and stability of the curcumin in the commercial

462

formulations was then calculated from this data. The initial amount of curcumin in each of the

463

original commercial products was different: 8.8, 6.6 and 21.8% for NM, FS, and Win,

464

respectively. For this reason, the samples were mixed with different levels of distilled water

465

prior to being exposed to the simulated GIT so that each one contained the same final amount of

466

curcumin (150 µg /g water) as in the nanoemulsions.

467

Analysis of the amount of digestible materials in the commercial supplements was carried

468

out using the pH stat method. However, only a small volume of 0.25 M NaOH solution had to

469

be added to maintain the samples at neutral pH throughout the small intestine phase (< 0.6 mL),

470

which suggested that there was little or no digestible material present (data not shown). This

471

would be expected because most of the inactive ingredients present in the supplements were

472

indigestible. Presumably, the proteins in those samples that contained gelatin (NM and FS) had

473

already been digested by pepsin in the stomach phase before they reached the small intestine

474

phase.

475

Properties mixed micelles and digest of commercial curcumin


16


476

Page 18 of 36

The absolute amount of curcumin solubilized in the mixed micelles by the end of the small

477

intestine phase decreased in the following order for the different supplements: Win >> FS > NM

478

(Fig. 7). This effect can mainly be attributed to differences in the initial water-dispersibility of

479

the products. A large amount of sediment was observed at the bottom of the test tubes

480

containing the NM supplements throughout the in vitro study, whereas, no precipitate was

481

observed for the FS and Win supplements (Fig. 8). This result suggests that the majority of

482

curcumin from the NM supplements remained in the sediment and was not solubilized in the

483

mixed micelles. The FS supplement had a significantly higher curcumin concentration in the

484

mixed micelle phase than the NM supplement. This suggests that the presence of the non-ionic

485

surfactant (polysorbate 80) increased the solubility of curcumin in the mixed micelles. The

486

curcumin in the Win sample gave the highest curcumin concentration in the mixed micelles,

487

which could be due to multiple reasons. First, PVP forms polymeric micelles that can

488

encapsulate hydrophobic curcumin molecules and enhance their solubility in the mixed micelle

489

phase 46, 48. Second, mixed tocopherols act as an antioxidant that protects curcumin from

490

chemical degradation within the intestinal environment 49. Other studies have also reported that

491

the stability and bioaccessibility of curcumin can be improved by co-encapsulating it with

492

antioxidants in colloidal delivery systems 9, 47, 48, 50.

493

Interestingly, the total concentration of curcumin in the overall digest followed an opposite

494

trend to that observed for the mixed micelles: NM > FS ≈ Win (Fig. 7). Initially, all the samples

495

had the same initial curcumin concentration (150 µg/g), which suggests that some of the

496

curcumin had chemically degraded after exposure to the mouth, stomach, and small intestine

497

phases. The relatively high concentration of curcumin in the digest for the NM sample may have

498

been because it was insoluble and therefore more stable to chemical degradation (Fig. 8).

499

Conversely, the curcumin in the FS and Win samples was trapped inside small colloidal particles

500

with a relatively high specific surface area and therefore were more susceptible to chemical

501

degradation due to the presence of reactive substances in the surrounding aqueous phase. It is

502

known that curcumin is chemically unstable under neutral pH conditions, such as those found in

503

the mouth and intestinal phases 1.

504

Bioaccessibility and Stability

505 506

The bioaccessibility and stability of the curcumin in the commercial products was calculated based on the curcumin concentrations in the initial, raw digest, and mixed micelle phases. The


17

Page 19 of 36


507

bioaccessibility of the curcumin from the Win (74%) sample was significantly higher than that

508

from the FS (32%) and NM (10%) samples (Fig. 7). Again, this can be attributed to the ability of

509

the amphiphilic polymer (PVP) used in this product to facilitate the formation of micelles that

510

enhance the solubility of curcumin in the GIT. Conversely, the bioaccessibility of curcumin was

511

lowest in the NM sample because it contained crystals that were difficult to solubilize. The

512

stability of the curcumin was slightly higher in the NM product than in the FS and Win products,

513

which can again be attributed to the fact that some of the curcumin was present in a crystalline

514

form and was therefore more resistant to chemical degradation.

515

Comparison of curcumin-loaded nanoemulsions and commercial supplements

516

Finally, the effectiveness of the curcumin-loaded nanoemulsions developed in this study was

517

compared with the commercially available supplements for their ability to enhance the

518

bioaccessibility and stability of curcumin. The absolute amount of curcumin solubilized in the

519

mixed micelle phase decreased in the following order: Win ≈ pH-driven > heat-driven >

520

conventional >> FS > NM. Thus, the nanoemulsions were better or similar to the commercial

521

supplements at solubilizing the curcumin. This was probably because the triacylglycerols in the

522

lipid particles were converted into monoacylglycerols and free fatty acids that increased the

523

solubilization capacity of the mixed micelles. Conversely, the total amount of curcumin present

524

in the digest tended to be higher for the commercial supplements: NM > Win ≈ FS ≈ pH-driven >

525

heat-driven > conventional. This suggests that there was less chemical degradation of the

526

curcumin in the commercial supplements, which may have been because the curcumin was in a

527

crystalline form or because they contained antioxidants.

528

The bioaccessibility of curcumin calculated from this data decreased in the following order:

529

pH-driven ≈ heat-driven ≈ conventional ≈ Win >> FS > NM. These results suggest that all the

530

nanoemulsions gave bioaccessibilities that were as good as the best commercial formulation and

531

better than the other two. The stability of the curcumin was fairly similar in both the

532

nanoemulsions and the commercial supplements ranging from about 76 to 92%.

533

In summary, this study demonstrated that curcumin nanoemulsions could be prepared using

534

three different loading methods: conventional, heat-driven, or pH-driven. The pH-driven method

535

was the simplest to implement and gave the highest encapsulation efficiency. This was because

536

it did not involve any heating step, whereas the other two methods involved a step where the

537

curcumin was held at an elevated temperature either in oil or an emulsion. The curcumin


18


Page 20 of 36

538

nanoemulsion prepared by the pH-driven method gave a significantly higher curcumin

539

concentration in the mixed micelles phase after exposure to a simulated GIT. All the

540

nanoemulsions developed in this study gave bioaccessibilities that were similar to those of the

541

best commercial formulation tested. However, our nanoemulsions were formulated entirely from

542

natural ingredients, which may be beneficial for some consumer applications.

543

It should be noted that the different curcumin formulations were only tested using a

544

relatively simple static in vitro gastrointestinal model. This model cannot accurately simulate the

545

complex events occurring within the human GIT, particularly metabolism carried out by Phase I

546

and Phase II enzymes and absorption within the small intestine and colon. Future studies should

547

therefore focus on testing the different formulations using more realistic animal or human

548

feeding studies.

549

CONFLICT OF INTEREST STATEMENT

550

The authors state no conflict of interest.

551

FUNDING

552

This material was partly based upon work supported by the National Institute of Food and

553

Agriculture, USDA, Massachusetts Agricultural Experiment Station (MAS00491) and USDA,

554

AFRI Grants (2016-08782).

555 556 557 558 559


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560


REFERENCES

561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601

1. Heger, M.; van Golen, R. F.; Broekgaarden, M.; Michel, M. C., The molecular basis for the pharmacokinetics and pharmacodynamics of curcumin and its metabolites in relation to cancer. Pharmacological reviews 2014, 66, 222-307. 2. Epstein, J.; Sanderson, I. R.; MacDonald, T. T., Curcumin as a therapeutic agent: the evidence from in vitro, animal and human studies. British journal of nutrition 2010, 103, 15451557. 3. Kunnumakkara, A. B.; Anand, P.; Aggarwal, B. B., Curcumin inhibits proliferation, invasion, angiogenesis and metastasis of different cancers through interaction with multiple cell signaling proteins. Cancer letters 2008, 269, 199-225. 4. Sharma, R.; Gescher, A.; Steward, W., Curcumin: the story so far. European journal of cancer 2005, 41, 1955-1968. 5. Hsieh, C.-Y., Phase I clinical trial of curcumin, a chemopreventive agent, in patients with high-risk or pre-malignant lesions. Anticancer research 2001, 21, 2895-2900. 6. Tønnesen, H. H.; Másson, M.; Loftsson, T., Studies of curcumin and curcuminoids. XXVII. Cyclodextrin complexation: solubility, chemical and photochemical stability. International Journal of Pharmaceutics 2002, 244, 127-135. 7. Zou, L.; Zheng, B.; Liu, W.; Liu, C.; Xiao, H.; McClements, D. J., Enhancing nutraceutical bioavailability using excipient emulsions: Influence of lipid droplet size on solubility and bioaccessibility of powdered curcumin. Journal of Functional Foods 2015, 15, 72-83. 8. Gupta, N. K.; Dixit, V. K., Bioavailability enhancement of curcumin by complexation with phosphatidyl choline. Journal of pharmaceutical sciences 2011, 100, 1987-1995. 9. Vasconcelos, T.; Sarmento, B.; Costa, P., Solid dispersions as strategy to improve oral bioavailability of poor water soluble drugs. Drug discovery today 2007, 12, 1068-1075. 10. Shaikh, J.; Ankola, D.; Beniwal, V.; Singh, D.; Kumar, M. R., Nanoparticle encapsulation improves oral bioavailability of curcumin by at least 9-fold when compared to curcumin administered with piperine as absorption enhancer. European Journal of Pharmaceutical Sciences 2009, 37, 223-230. 11. Sun, D.; Zhuang, X.; Xiang, X.; Liu, Y.; Zhang, S.; Liu, C.; Barnes, S.; Grizzle, W.; Miller, D.; Zhang, H.-G., A novel nanoparticle drug delivery system: the anti-inflammatory activity of curcumin is enhanced when encapsulated in exosomes. Molecular Therapy 2010, 18, 16061614. 12. Esmaili, M.; Ghaffari, S. M.; Moosavi-Movahedi, Z.; Atri, M. S.; Sharifizadeh, A.; Farhadi, M.; Yousefi, R.; Chobert, J.-M.; Haertlé, T.; Moosavi-Movahedi, A. A., Beta casein-micelle as a nano vehicle for solubility enhancement of curcumin; food industry application. LWT-food science and technology 2011, 44, 2166-2172. 13. Huang, Y.; Dai, W.-G., Fundamental aspects of solid dispersion technology for poorly soluble drugs. Acta Pharmaceutica Sinica B 2014, 4, 18-25. 14. Kurien, B. T.; Singh, A.; Matsumoto, H.; Scofield, R. H., Improving the solubility and pharmacological efficacy of curcumin by heat treatment. Assay and drug development technologies 2007, 5, 567-576.


20


602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644

Page 22 of 36

15. Zou, L.; Liu, W.; Liu, C.; Xiao, H.; McClements, D. J., Utilizing food matrix effects to enhance nutraceutical bioavailability: increase of curcumin bioaccessibility using excipient emulsions. Journal of agricultural and food chemistry 2015, 63, 2052-2062. 16. Zou, L. Q.; Zheng, B. J.; Zhang, R. J.; Zhang, Z. P.; Liu, W.; Liu, C. M.; Xiao, H.; McClements, D. J., Enhancing the bioaccessibility of hydrophobic bioactive agents using mixed colloidal dispersions: Curcumin-loaded zein nanoparticles plus digestible lipid nanoparticles. Food Research International 2016, 81, 74-82. 17. Khan, F. I.; Ghoshal, A. K., Removal of volatile organic compounds from polluted air. Journal of loss prevention in the process industries 2000, 13, 527-545. 18. Shen, T. T., Industrial pollution prevention. In Industrial Pollution Prevention, Springer: 1995; pp 15-35. 19. Luo, Y.; Pan, K.; Zhong, Q., Casein/pectin nanocomplexes as potential oral delivery vehicles. International journal of pharmaceutics 2015, 486, 59-68. 20. Peng, S.; Li, Z.; Zou, L.; Liu, W.; Liu, C.; McClements, D. J., Enhancement of Curcumin Bioavailability by Encapsulation in Sophorolipid-Coated Nanoparticles: An in Vitro and in Vivo Study. Journal of agricultural and food chemistry 2018, 66, 1488-1497. 21. Cheng, C.; Peng, S.; Li, Z.; Zou, L.; Liu, W.; Liu, C., Improved bioavailability of curcumin in liposomes prepared using a pH-driven, organic solvent-free, easily scalable process. RSC Advances 2017, 7, 25978-25986. 22. Pan, K.; Luo, Y.; Gan, Y.; Baek, S. J.; Zhong, Q., pH-driven encapsulation of curcumin in selfassembled casein nanoparticles for enhanced dispersibility and bioactivity. Soft Matter 2014, 10, 6820-6830. 23. Priyadarsini, K. I., The chemistry of curcumin: from extraction to therapeutic agent. Molecules 2014, 19, 20091-20112. 24. Zebib, B.; Mouloungui, Z.; Noirot, V., Stabilization of curcumin by complexation with divalent cations in glycerol/water system. Bioinorganic chemistry and applications 2010, 2010. 25. Li, Y.; Hu, M.; McClements, D. J., Factors affecting lipase digestibility of emulsified lipids using an in vitro digestion model: Proposal for a standardised pH-stat method. Food Chemistry 2011, 126, 498-505. 26. Jurenka, J. S., Anti-inflammatory properties of curcumin, a major constituent of Curcuma longa: a review of preclinical and clinical research. Alternative medicine review 2009, 14. 27. Kaptay, G., A new paradigm on the chemical potentials of components in multi-component nano-phases within multi-phase systems. Rsc Advances 2017, 7, 41241-41253. 28. Yang, Y.; Leser, M. E.; Sher, A. A.; McClements, D. J., Formation and stability of emulsions using a natural small molecule surfactant: Quillaja saponin (Q-Naturale®). Food Hydrocolloids 2013, 30, 589-596. 29. Mitra, S.; Dungan, S. R., Micellar properties of Quillaja saponin. 1. Effects of temperature, salt, and pH on solution properties. Journal of agricultural and food chemistry 1997, 45, 15871595. 30. McClements, D. J., Food emulsions: principles, practices, and techniques. CRC press: 2015. 31. McClements, D. J.; Decker, E. A.; Park, Y., Controlling lipid bioavailability through physicochemical and structural approaches. Critical reviews in food science and nutrition 2008, 49, 48-67.


21

Page 23 of 36

645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687


32. Silletti, E.; Vingerhoeds, M. H.; Norde, W.; Van Aken, G. A., The role of electrostatics in saliva-induced emulsion flocculation. Food Hydrocolloids 2007, 21, 596-606. 33. Vingerhoeds, M. H.; Blijdenstein, T. B.; Zoet, F. D.; van Aken, G. A., Emulsion flocculation induced by saliva and mucin. Food Hydrocolloids 2005, 19, 915-922. 34. Bauer, E.; Jakob, S.; Mosenthin, R., Principles of physiology of lipid digestion. AsianAustralasian Journal of Animal Sciences 2005, 18, 282-295. 35. Maldonado-Valderrama, J.; Wilde, P.; Macierzanka, A.; Mackie, A., The role of bile salts in digestion. Advances in Colloid and Interface Science 2011, 165, 36-46. 36. Salvia-Trujillo, L.; Qian, C.; Martín-Belloso, O.; McClements, D., Influence of particle size on lipid digestion and β-carotene bioaccessibility in emulsions and nanoemulsions. Food chemistry 2013, 141, 1472-1480. 37. McClements, D. J.; Li, Y., Structured emulsion-based delivery systems: Controlling the digestion and release of lipophilic food components. Advances in colloid and interface science 2010, 159, 213-228. 38. Sharma, R. A.; Steward, W. P.; Gescher, A. J., Pharmacokinetics and pharmacodynamics of curcumin. Molecular Targets and Therapeutic Uses of Curcumin in Health and Disease 2007, 595, 453-470. 39. Andersen, C. N., Vitamin and mineral dietary supplement and method of making. In Google Patents: 1946. 40. Desai, D.; Kothari, S.; Huang, M., Solid-state interaction of stearic acid with povidone and its effect on dissolution stability of capsules. International journal of pharmaceutics 2008, 354, 77-81. 41. Li, J.; Wu, Y., Lubricants in pharmaceutical solid dosage forms. Lubricants 2014, 2, 21-43. 42. Shokri, J.; Adibkia, K., Application of cellulose and cellulose derivatives in pharmaceutical industries. In Cellulose-medical, pharmaceutical and electronic applications, InTech: 2013. 43. Jannin, V.; Chevrier, S.; Michenaud, M.; Dumont, C.; Belotti, S.; Chavant, Y.; Demarne, F., Development of self emulsifying lipid formulations of BCS class II drugs with low to medium lipophilicity. International Journal of Pharmaceutics 2015, 495, 385-392. 44. Gómez-Estaca, J.; Gavara, R.; Hernández-Muñoz, P., Encapsulation of curcumin in electrosprayed gelatin microspheres enhances its bioaccessibility and widens its uses in food applications. Innovative Food Science & Emerging Technologies 2015, 29, 302-307. 45. Dave, R. H., Overview of pharmaceutical excipients used in tablets and capsules. Drug Topics, Oct 2008, 24, 1-13. 46. Schwarz, W., PVP: a critical review of the kinetics and toxicology of polyvinylpyrrolidone (povidone). CRC Press: 1990. 47. Paradkar, A.; Ambike, A. A.; Jadhav, B. K.; Mahadik, K., Characterization of curcumin–PVP solid dispersion obtained by spray drying. International journal of pharmaceutics 2004, 271, 281-286. 48. Gangwar, R. K.; Dhumale, V. A.; Kumari, D.; Nakate, U. T.; Gosavi, S.; Sharma, R. B.; Kale, S.; Datar, S., Conjugation of curcumin with PVP capped gold nanoparticles for improving bioavailability. Materials Science and Engineering: C 2012, 32, 2659-2663. 49. Ak, T.; Gülçin, İ., Antioxidant and radical scavenging properties of curcumin. Chemicobiological interactions 2008, 174, 27-37.


22


688 689 690

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50. Croy, S.; Kwon, G., Polymeric micelles for drug delivery. Current pharmaceutical design 2006, 12, 4669-4684.


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TABLES AND FIGURES Conventional

Heat-Driven

pH-Driven

Initial curcumin concentration (µg/mL)

83.3 ± 10.8 a

114.3 ± 8.5 b

139.7 ± 3.8 c

Encapsulation Efficiency (%)

55.5 ± 7.2 a

76.2 ± 5.2 b

93.2 ± 2.3 c

L*

121.2 ±0.5c

118.9 ± 0.2b

117.8 ± 0.3a

b*

72.7 ± 0.5 a

87.0 ± 0.2 b

92.2 ± 1.8 c

D32 (µm)

0.17 ± 0.02 a

0.20 ± 0.00 b

0.18 ± 0.01 ab

ζ- potential (mV)

-45.2 ± 1.3 a

-44.6 ± 1.7 a

-45.3 ± 1.8 a

Table 1. Influence of fabrication method on the initial curcumin concentration, loading capacity, tristimulus color value (b*), mean particle diameter (D32) and electrical characteristics (ζpotential) of curcumin lipid nanoparticles. Samples designated with different letters are significantly different (Duncan, p

Impact of delivery system type on curcumin bioaccessibility

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