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Tunable physical properties of ethylcellulose/ gelatin composite nanofibers by electrospinning Yuyu Liu, Lingli Deng, Cen Zhang, Fengqin Feng, and Hui Zhang J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b06038 • Publication Date (Web): 09 Feb 2018 Downloaded from http://pubs.acs.org on February 13, 2018

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Journal of Agricultural and Food Chemistry

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Tunable physical properties of ethylcellulose/gelatin composite nanofibers

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by electrospinning

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Yuyu Liu, Lingli Deng, Cen Zhang, Fengqin Feng, Hui Zhang *

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College of Biosystems Engineering and Food Science, Fuli Institute of Food Science, Zhejiang Key

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Laboratory for Agro-Food Processing, Zhejiang R&D Center for Food Technology and Equipment,

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Zhejiang University, Hangzhou 310058, China

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* Corresponding author. E-mail: [email protected]. Telephone: +86-571-88982981; fax:

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+86-571-88982981.

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1

ACS Paragon Plus Environment


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Abstract

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In this work, the ethylcellulose/gelatin blends at various weight ratios in water/ethanol/acetic

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acid solution were electrospun to fabricate nanofibers with tunable physical properties. The

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solution compatibility was predicted based on Hansen solubility parameters and evaluated by

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rheological measurements. The physical properties were characterized by scanning electron

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microscopy, porosity, differential scanning calorimetry, thermogravimetry, Fourier transform

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infrared spectroscopy, and water contact angle. Results showed that the entangled structures

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among ethylcellulose and gelatin chains through hydrogen bonds gave rise to a fine morphology of

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the composite fibers with improved thermal stability. The fibers with higher gelatin ratio (75%)

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possessed hydrophilic surface (water contact angle of 53.5°) and adequate water uptake ability

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(1234.14%), while the fibers with higher ethylcellulose proportion (75%) tended to be highly

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water stable with a hydrophobic surface (water contact angle of 129.7°). This work suggested that

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the composite ethylcellulose/gelatin nanofibers with tunable physical properties have potentials as

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materials for bioactive encapsulation, food packaging and filtration applications.

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Keywords

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Ethylcellulose, gelatin, electrospinning, compatibility, physical property

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Introduction

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Electrospinning is the technique of using high potential electric field to disintegrate polymer

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solution into fine fibers.1 This technique involves the use of high-voltage source, a capillary, a pump

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and a grounded collector. During electrospinning, polymer solution is constantly extruded from a

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capillary by a pump, forming a charged cone-shaped droplet known as the Taylor cone caused by

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high-voltage. Two main forces fight on the charged droplet, one is a drag force called electrostatic

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force, and the other is the surface tension, leading to contraction of the droplet. Once the drag force

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counteracts the surface tension, a charged polymer jet is ejected from the Taylor cone and is

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transited toward collector. During the transit, the jet suffers from distortion, expansion and solvent

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evaporation, leading to thin fibers with diameters ranging from micrometers to nanometers.2, 3 The

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fabricated thin fibers usually possess fascinating features such as high porosity, high

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surface-to-volume ratio, and ultrafine structures.4-7 These unique properties make the electrospun

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fibers an ideal candidate for active food packaging, edible coatings, encapsulation, biomedicine, and

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filtration membranes.3, 6, 8

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As a FDA approved biopolymer with excellent biodegradability, biocompatibility and

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non-immunogenicity, gelatin has been electrospun for biomedical applications involving tissue

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scaffolds, wound healing and health caring devices.6, 9 However, the extremely water instability and

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thermo-sensitivity of gelatin nanofibers have significantly limited the utilization in food packaging

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and encapsulation of temperature-sensitive components.8 Hence, a few reports have suggested

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blending or cross-linking gelatin with other materials, such as cellulose or its derivatives.10, 11

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Ethylcellulose, as one of cellulose derivatives, is a perfect candidate as blending material due

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to its nontoxicity, hydrophobicity, high flexibility, thermoplasticity and film forming ability, 3



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exhibiting various applications in food, microencapsulation, filtration and pharmaceutics.12,

13

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Zhang et al. found that the casted film of ethylcellulose blended with poly(propylene carbonate)

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exhibited an enhanced thermal decomposition temperature due to the contribution of thermoplastic

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ethylcellulose.14 The improved water stability of zein fibers by co-electrospinning with

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ethylcellulose was reported by Lu et al., who showed that the composite nanofibers possessed a

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favored sustained hydrophobic drug release profile.15

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It has been reported that good solution compatibility contributes to improved spinnability,

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leading to excellent morphology and regular shape of fibers.16, 17 Thus, before electrospinning, a

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prediction of the polymer compatibility in solution is necessary. The Hansen solubility parameters

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(HSPs), involving three components of dispersive (δd), polar (δp) and hydrogen bonding (δh)

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energies, have been confirmed as a promising method for calculation of solution compatibility.

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Wang et al. suggested that the HSPs were more precise to interpret dispersion behavior of

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nanoparticles in solvents than qualitative descriptions.18 The HSPs may serve as tools to develop

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polymeric adhesives,19 interpenetrating polymer networks,20 and polymerization reactions.21 The

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total HSP value (δt) is defined as the square root of the sum of the three squared components as

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follows:18 δ = δ + δ + δ (1)

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In this study, the ethylcellulose/gelatin composite nanofibers at various weight ratios were

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fabricated by electrospinning. The solution compatibility was predicted based on HSPs calculations,

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and evaluated by viscosity measurements. The characterization of the electrospun nanofibers was

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conducted using scanning electron microscopy (SEM), thermogravimetric analysis (TGA),

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differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, water 4


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contact angle (WCA), porosity and water vapor transmission rate. The nanofibers were then

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immersed in water to investigate the properties of surface swelling, water uptake, and weight loss.

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Materials and Methods

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Materials. Ethylcellulose (3 - 7 cP, MW, 20 - 30 kDa) and gelatin (Type B, Bloom 250, MW,

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100 kDa) were obtained from Aladdin, Inc. (Shanghai, China). Ethanol absolute and acetic acid

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(99.8%) were purchased from Sinopharm Chemical Reagent Co., Ltd., China. Deionized water was

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used throughout the experiments. All materials were used without further purification.

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Solution Preparation. The solvent volume ratio of water/ethanol/acetic acid was set to 2/2/6

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(v/v/v). Blends of ethylcellulose and gelatin at weight ratios of 0/1, 1/3, 1/1, 3/1 and 1/0 (denoted as

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EG01, EG13, EG11, EG31 and EG10, respectively) were dissolved in the solvent solution at a total

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concentration of 30 wt% (w/v). The solutions were constantly stirred at a room temperature of

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25 °C to ensure complete dissolution of polymers.

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Rheology. The rheological measurements were performed at 25 °C using an Anton Paar

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MCR302 rheometer (Anton Paar, Austria, QC) across a shear rate range of 1 - 100 s−1 using 1%

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strain. The zero shear viscosity was taken as the average viscosity obtained at a shear rate occurred

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at 1 s−1.

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Electrospinning. The laboratorial electrospinning equipment consisted of a high-voltage

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power supply (Gamma High Voltage, USA), a syringe connected with a pump (LSP02-1B, Baoding

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Longer Precision Pump Co., Ltd., China), and a grounded collector. Electrospinning parameters of

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all solutions were set as follows: an applied voltage of 15 kV, a feed rate of 1.0 mL/h, and a

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tip-to-collector distance of 100 mm. 4 ml of the prepared solutions was electrospun onto a grounded

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cylindrical aluminum foil at room temperature with a humidity of 50%. The collected nanofibers 5



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were then stored in a desiccator to remove the residual solvents before characterization.

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Fiber Morphology. The fiber morphology was observed using a field emission scanning

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electron microscope (SEM, SU8010, Hitachi, Japan). The fiber diameters from SEM images were

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measured by Nano Measure software. The average diameter and size distribution of fibers were

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calculated by measuring 120 fibers at random.

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Porosity. The porosity of fibers was determined by the previously reported method with

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modifications.22, 23 Three specimens for each fiber mat were tested. Here, the specimens were cut

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into round pieces with a diameter of 15 mm and weighted. The thickness at minimum three different

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places was measured using a thickness meter (C640, Labthink, China). The appear density (ρA) was

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the mass to volume ratio of the mat, while the real density (ρR) was determined on the basis of

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gelatin density (1.41 g/cm3) and ethylcellulose density (1.14 g/cm3) by mass fraction. The equation

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used to determine the porosity was as follows: porosity = 1 −

ρ × 100% (2) ρ

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Thermal Behaviors. The thermal behaviors were investigated using differential scanning

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calorimetry (DSC，TA-Q500, USA) and thermogravimetric analysis (TGA, TA-Q500, USA). For

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TGA analysis, the samples (2 - 3 mg) were heated from 50 °C to 600 °C at a rate of 10 °C/min

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under a dynamic nitrogen atmosphere. For DSC analysis, the samples (6 - 8 mg) were heated from 0

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- 250 °C at 10 °C/min under a nitrogen atmosphere at a flow rate of 50 mL/min.

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Fourier Transform Infrared Spectroscopy. The nanofiber mats were evaluated using a

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Fourier Transform Infrared Spectrometer (FTIR, Nicolet 170-SX, Thermo Nicolet Ltd., USA). The

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spectra were recorded with 16 scans at a resolution of 4 cm−1 in the range of 4000 - 400 cm−1.

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Water Contact Angle. The water contact angle (WCA) was conducted at room temperature 6


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using a surface tension meter (DCAT-21, Delta Phase, Germany) with Milli-Q water (3 µL) as the

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probe liquid. The equilibration time of the droplet was 15 s.

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Water Evaporation. The water vapor transmission rate (WVTR) was determined with a Water

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Vapor Transmission Rate Tester (W3/30, Labthink, China) at 25 °C with 80% relative humidity. All

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measurements were performed in triplicate.

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Water Stability. The fiber mats were cut into round piece with a diameter of 15 mm (D0) and

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weighted (W0), and then immersed in water for 10 days at room temperature with a shaking speed at

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150 rmp. During the immersion, water was added to maintain a constant volume after withdrawing

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aliquots from the solution for quantitative analysis using a BCA protein assay kit (Pierce, Rockford,

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IL) and a microplate reader (MDS ANALYTICAL, America). The pure ethylcellulose (EG10) fiber

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sample was used as control. The gelatin weight loss (GL) was calculated using the following

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equation: G,! =

M!# ⁄M! ( × 100% (3) M&' Φ! × M&'

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Where Mi and Mit represent the original mat weight and the gelatin mass loss at the t time for

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the sample numbered for i, respectively; M01 and M01∞ are the original mass and the terminal gelatin

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mass loss of the EG01 sample, respectively; Φi represents the gelatin fraction of each sample

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compared with the EG01 sample.

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After 10 days immersion, digital photographs were taken to measure diameter (DT) using Nano

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Measure software, the wet weight of the samples (Ww) was immediately measured. Then samples

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were dried at 60 °C for 2 hours and their weights were recorded (WD). The samples were stored in a

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desiccator prior to SEM examinations. The surface welling (SW), water-uptake capacity (WT), and

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weight loss (WL) were calculated as follows:24-26 7



D D π × (( 2. ) − ( 2& ) ) S+ = (4) D π × ( & ) 2 W1 − W2 W. = (5) W2 W& − W2 W = × 100% (6) W& 138

Statistical Analysis. The data were presented as mean ± standard deviation of three different

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measurements. The statistical analysis was carried out using analysis of variance at the 0.05

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significance level. All the plots were analyzed using Origin pro8 software.

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Results and discussion

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Solution Compatibility. The Hansen solubility parameters (HSPs), split into dispersive (δd),

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polar (δp) and hydrogen bonding (δh) energies, is commonly used for the prediction of solution

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compatibility. The total HSP value (δt) is defined as the square root of the sum of the three squared

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components. The closer the HSPs values of two species are, the greater their compatibility is, as

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calculated below:21, 27, 28 (R 6 ) = 4 × (δ2 − δ2' ) + (δ7 − δ7' ) + (δ8 − δ8' ) (7)

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The concept has been extended from the mixing of polymers with liquid with a total HSPs defined as follows:29 δ:!; = < ∅! δ#,! (8)

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Where Φ represents the volume (weight) ratio of each solvent or polymer in solution.

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The published HSPs of the used solvents and polymers in this work were presented in Table 1

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(A), and the calculated difference in HSPs between polymers and solvents was shown in Table 1 (B).

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Based on this theory, blending ethylcellulose with gelatin in the water/ethanol/acetic acid solution

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gave rise to smaller Ra compared with the pure ethylcellulose or gelatin solution, suggesting 8


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improved compatibility of the composite. Interestingly, a minimum Ra occurred in the case of EG11,

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indicating the highest compatibility of the ethylcellulose/gelatin mixture in solution. Gravelle et al.

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reported that for a polymer gel network based on hydrogen bonds such as ethylcellulose-based

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systems, the δh played a decisive role in determining solution compatibility.27 Hence, the higher |δh|

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of the EG31 solution might imply a weaker compatibility, compared with the EG13 or EG11

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solution.

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It is universally accepted that the viscosity of solution was another reliable and desirable

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method to decide solution compatibility for a ternary (polymer-polymer-solvent) system.16 The

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viscosity measurements have been applied to confirm the availability of the HSPs in prediction of

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solution compatibility.30 Thus, the rheological experiments were performed and the results were

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presented in Table 1 (B). The apparent viscosities of the EG01, EG13, EG11, EG31 and EG10

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solutions were 2.51, 6.74, 5.24, 13.40 and 8.53 Pa·s, respectively. When the weight ratio of

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ethylcellulose content was less than 50%, the viscosity of the blend was higher than that of the

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gelatin solution and lower than that of the ethylcellulose solution, indicating good compatibility on

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blending.16 Further, a minimum viscosity was obtained when increasing the ethylcellulose ratio up

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to 50%, indicating the enhanced solution compatibility due to the reduced intramolecular and

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intermolecular forces of gelatin, and the increased entanglements among ethylcellulose and gelatin.

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Ge

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(PBMA)/polyacrylonitrile (PAN) systems with increasing PBMA content suggested good

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compatible, due to the fact that the entry of PBMA molecules within the PAN threw apart the

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regularly arranged chains of PAN and broke up the molecular alignment to a certain extent.20

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However, when the weight ratio of ethylcellulose was 75%, the viscosity of the blend was higher

et

al.

reported

that

the

reduced

viscosity

of

9


the

poly(n-butyl

methacrylate)


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than that of the ethylcellulose or gelatin solution due to the decreased flexibility of gelatin chains

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caused by ethylcellulose with poor fluidity, indicating poor solution compatibility. Therefore, these

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results suggested that the best solution compatibility was for EG11, while the weakest for EG31, in

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good agreement with the HSPs prediction.

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Fiber Morphology. The morphology of the ethylcellulose/gelatin composite fibers was

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displayed in Figure 1. Visually, the fiber mats appeared to be white-colored with film-like structures,

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while the SEM images showed a highly-porous structure due to the randomly-oriented and

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interlocking fibers. The pure gelatin (EG01) fibers were homogeneous with an average diameter of

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653.5 nm, while the pure ethylcellulose (EG10) fibers were spindle-like structures with an average

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diameter of 412.9 nm. The composite fibers (EG13, EG11 and EG31) had regular morphologies at

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average diameters of 550.0, 459.2 and 560.4 nm, respectively. Notably, the EG11 fibers were the

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most uniform and thinnest. This is in agreement with the results of Atila et al., who found that the

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most homogeneous fiber morphology was obtained at pullulan/cellulose acetate at a weight ratio of

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1/1, while the other weight ratios resulted in phase separation preventing uniformity of fibers.25

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Ghorani et al. demonstrated that the increased inter-chain interactions served to stabilize the

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physical entanglements leading to enhanced compatibility, resulting in a bead-free morphology with

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improved spinnability.1, 31 Chang et al. reported that the bacteria cellulose/gelatin composite films

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provided an interpenetrating network, in which bacteria cellulose supported as scaffold with gelatin

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filled in through hydrogen bonds.11 Therefore, the spindle-free morphology after blending

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ethylcellulose with gelatin might be due to the increased solution compatibility caused by the

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intermolecular interactions such as hydrogen bonds among the molecular chains between gelatin

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and ethylcellulose. Chen et al. reported that good compatibility between polyamide 6 (PA6) and 10


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polyethylene glycol (PEG) improved the spinnability of electrospinning, leading to uniform fibers

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with regular shape.17 Additionally, the fiber size reduction led to a high specific surface area,

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suggesting attractive values for encapsulation of bioactive compounds, bimolecular sensors and

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ultra-filtration media.1

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Porosity. Corresponding to the SEM images in Figure 1, the porosity of the EG01, EG13,

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EG11, EG31 and EG10 fibers was 86.81%, 91.74%, 92.46%, 90.18% and 92.28%, respectively

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(Figure 2). This suggested that the thicker the fibers, the lower the porosity value. Yoon et al.

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observed that for the electrospun fibers, the thinnest fibers exhibited the highest porosity value.32 It

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is generally accepted that a high bulk porosity (up to 80%) encouraged adequate diffusion of

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nutrition, vapor and waste transport, desirable for many applications involving filtration, sensors

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and biological substrates.23,

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terephthalate) nanofibers as filtration membrane for apple juice clarification, due to the distinct

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characteristics such as high porosity and large surface area.34

32, 33

Veleirinho et al. reported an application of poly(ethylene

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Thermal Behaviors. The TGA behaviors of the electrospun fibers given in Figure 3 (A) and

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Table 2 (A) were divided into three stages. The first stage at a temperature range of 0 - 160 °C was

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related to the loss of volatile components by evaporation.35 It was clear that the increase in

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ethylcellulose content resulted in the reduced mass loss of nanofibers. In the second stage at 160 -

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380 °C, the thermal events were most possibly associated with the decomposition of molecular

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chains.36 The decomposition temperatures of the pure gelatin (EG01) and ethylcellulose (EG10)

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fibers were 311.82 °C and 349.18 °C, respectively. However, the decomposition temperatures of the

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EG13, EG11 and EG31 fibers were 353.01, 355.16 and 352.41 °C, respectively, indicating the

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improved thermal decomposition stability of the composite fibers. This is in agreement with the 11



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results reported by Zhang et al., who demonstrated an elevated thermal decomposition temperature

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upon blending ethylcellulose with poly(propylene carbonate).14 The third (T > 380 °C) stage was

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attributed to the carbonation reactions.37

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The DSC results were shown in Figure 3 (B) and Table 2 (B). The broad endothermic peak, due

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to evaporation of volatiles or bound water, was termed as dehydration event (ED). The ED of the

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EG13, EG11 and EG31 fibers appeared at 127.22, 112.40 and 107.70 °C , respectively,38 indicating

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that the higher the ethylcellulose content, the less pronounced ED of the composite fibers. The glass

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transition temperature of the EG10 fibers at 123.47 °C was followed by a melting temperature at

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190.05 °C, suggesting a semi-crystallite behavior of ethylcellullose, in agreement with the previous

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studies reporting presence of an ‘‘ordered’’ crystallite and a ‘‘disordered’’ amorphous areas in

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ethylcellulose.13 The characteristic melting peaks of the EG01 fibers at 60.31 °C and 213.34 °C

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were known as the denaturation and decomposition events, respectively.35,

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composite fibers, the characteristic glass transition event was not observed, while the melting peaks

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shifted to higher temperatures, especially for the EG11 fibers with the highest temperatures at

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66.10 °C and 218.35 °C, respectively. Davidovich et al. reported that the disappeared glass

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transition was related to the disorder/order transition of ethylcellulose caused by the rearrangement

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of inter-molecular network through intra-chain hydrogen bonds.13 Gravelle et al. ascribed the shift

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in the melting peak to the direct inter-chain interactions between composite systems, and suggested

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that the stronger the interactions, the more the peak-shifts.27 Jiang et al. argued that the molecular

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chains entangled between polycaprolactone and gelatin resulted in the increased melting

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temperatures of composite fibers compared with the pure polycaprolactone fibers.38 Therefore, our

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results indicated that blending ethylcellulose with gelatin in nanofibers has encouraged 12


39

As for all the

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inter-molecular interactions leading to the improved thermal stability.

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FTIR. The FTIR analysis of the electrospun nanofibers was illustrated in Figure 4. The

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characteristic absorption peaks of gelatin were related to C=O stretching at 1635 - 1650 cm−1

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(amide I), N-H bending at 1539 cm−1 (amide II) and C-N stretching at 1243 cm−1 (amide III),

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respectively 40. The band between 3600 - 3200 cm−1 was due to -OH stretching.11, 41 Compared with

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the pure gelatin (EG01) fibers, the EG13, EG11 and EG31 composite fibers showed the decreased

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intensities of the amide I and II bands, as well as an almost nonexistent amide III for EG11 and

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EG31 fibers. Additionally, the -OH stretching of the EG01 and EG10 fibers at 3303 and 3474 cm−1

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was shifted to 3330, 3381 and 3463 cm−1 in the case of the EG13, EG11 and EG31 fibers,

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respectively.

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It is known that the decreased intensities of amide bands are associated with the decreased

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helical conformation of gelatin chains, and the wavenumber shifts of the -OH bands are a measure

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of the average strength of the intra- and inter-molecular hydrogen bonds.9,

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observed changes in peak intensity and peak-shifts evidenced the occurrence of hydrogen bonds

256

among ethylcellulose and gelatin chains in nanofibers.

40

Therefore, the

257

Water Contact Angle. The results of surface wettability characterized by water contact angle

258

(WCA) were presented in Figure 5. The pure gelatin (EG01) fibers had a WCA of 38.5° due to its

259

extreme water instability.42 As a water stable material,15 the pure ethylcellulose (EG10) fibers

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showed a hydrophobic surface (WCA = 134.8°). In the case of the EG13 fibers, a hydrophilic

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surface at 53.5° was observed, while the EG11 and EG31 fibers gave WCA of 113.8° and 129.7°,

262

respectively, suggesting the hydrophobic surface. These results demonstrated that the increase in

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gelatin content caused the significant decrease in WCA, in agreement with the previous results for 13



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the gelatin based composite films, indicating that the higher the gelatin content, the higher the

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surface wettability.43 It is accepted that the hydrophilic fiber surface was usually favored for

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aqueous filtration applications due to the reduced protein adhesion and bio-fouling, while the

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surface hydrophobicity contributed to water stability.15, 44

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Water Evaporation. As presented in Figure 6, the water vapor transition rates (WVTR) of the

269

pure gelatin (EG01) and composite (EG13, EG11 and EG31) fibers were 530.62, 534.11, 544.58

270

and 499.20 g/m2·24 h, respectively, lower than that of the pure ethylcellulose (EG10) fibers (576.00

271

g/m2·24 h). Similarly, it was reported that the WVTR of the casted bacterial cellulose/gelatin films

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ranging from 592 to 885 g/m2·24 h at different gelatin contents were lower than the pure bacterial

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cellulose film (1026 g/m2·24).9 The differences in fiber porosity and fiber diameter might gave an

274

explanation to the changes in WVTR, the higher porosity and smaller fiber diameter were more in

275

favor of the increase in WVTR. Additionally, the coefficients of vapor permeability (WVPC) of

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each fibers were 8.41 × 10-12, 1.10 × 10-11, 1.00 × 10-11, 4.65 ×10-12 and 4.15 ×10-12 g·cm/cm2·s·Pa

277

at the ethylcellulose/gelatin weight ratio of 0/1, 1/3, 1/1, 3/1 and 1/0, respectively. Obviously,

278

increasing the gelatin content in the composite fibers caused an increase in WVPC. Similarly,

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Soradech et al. observed that for the shellac/gelatin composite films, the higher the gelatin content,

280

the higher WVPC was obtained, due to a greater amino content of gelatin, resulting in the higher

281

absorption of water molecules.43 In general, WVTR and WVPC parameters were correlated to

282

moisture retention and gas and fluid exchange.26

283

Water Stability. The SEM images of the electrospun fibers after immersed in water for 10 days

284

were shown in Figure 7, and the calculated surface swelling (SW), water-uptake capacity (WT) and

285

weight loss (WL) were presented in Table 3. After immersion, the pure gelatin (EG01) fibers were 14


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completely dissolved, confirming its water instability. With the increasing ethylcellulose content, a

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swelled and attached fiber surface was observed for the EG13 and EG11 fibers, while the EG31 and

288

EG10 fibers maintained the fibrous morphology, indicating a superior water stability contributed by

289

ethylcellulose. In Table 3, the negative values of SW were due to the size shrinkage of the fiber mats

290

after water immersion. With the increasing ethylcellulose content, the lower extent of shrinkage was

291

obtained. Similarly, the WL measurements reflected that the higher the ethylcellulose content, the

292

smaller the WL value. These results suggested that the composite fibers with higher ethylcellulose

293

content were more water stable since they were indicators of the dislocations or blistering and

294

sensitivity to water.26, 43 The excellent water barrier property of nanofibers was responsible for

295

retarding the surface dehydration of food products, suggesting promising applications in edible

296

packaging.45 As seen in Table 3, the water uptake ability increased significantly (p < 0.05) with the

297

increasing fraction of gelatin, probably due to the hydrophilicity of gelatin. This is in accordance

298

with the results of Soradech et al., who reported that in the composite shellac/gelatin film, the

299

higher gelatin content gave higher polarity and swelling capacity, thus attracting a higher amount of

300

water.43 The sufficient hydrophilicity and water uptake capacity of fibers were beneficial to improve

301

bio-adhesive, leading to a higher encapsulated compound bioavailability.1, 38

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The gelatin weight loss profile of nanofibers immersed in water for 10 days was presented in

303

Figure 7 (F). The loss of the pure gelatin (EG01) fibers showed a rapid increase within 1 day and

304

reached 100% after 4 days. However, the composite fibers exhibited less gelatin weight loss and

305

leveled off after 3 days of water immersion. Clearly, with the increasing content of ethylcellulose,

306

the gelatin weight loss decreased significantly (p < 0.05). Gelatin, a safe polymer with high

307

stabilizing activity, affinity biocompatibility and biodegradability, exhibits numerous applications in 15



308

food, biomaterial, adhesive, and pharmacy industries.9, 40 Hence, it is necessary to make sure of

309

sufficient gelatin stability for desired purpose.

310

In summary, the present work demonstrated that the ethylcellulose/gelatin composite

311

nanofibers with tunable physical properties may be fabricated by varying the weight ratios of

312

ethylcellulose and gelatin in the blend solutions. It was indicated that the better solution

313

compatibility resulted in the higher spinnability, leading to excellent morphology of fibers with

314

higher porosity. Generally, the composite fibers exhibited a uniform and highly-porous structure

315

with higher melting temperatures than the pure gelatin or ethylcellulose fibers, due to the

316

entanglement of molecular chains through hydrogen bonds. Notably, the fibers with higher gelatin

317

ratio possessed uniform morphology, adequate water uptake ability and vapor permeability, which

318

were beneficial to improve bio-adhesive of encapsulated compound for higher bioavailability and

319

reduce protein adhesion and bio-fouling, while the fibers with higher ethylcellulose proportion

320

showed hydrophobic surface, low water vapor permeability, and excellent water barrier property,

321

which were responsible for retarding the surface dehydration of food products. This work suggested

322

that the ethylcellulose/gelatin composite nanofibers may be used as promising materials for

323

bioactive encapsulation, food packaging and filtration applications.

324

Acknowledgement

325

This work was supported by the National Natural Science Foundation of China (Grant No.

326

31772013).

327

Conflict of interest

328 329

The authors declare no competing financial interest.

References 16


Page 16 of 37

Page 17 of 37


330

(1) Ghorani, B.; Tucker, N., Fundamentals of Electrospinning as a Novel Delivery Vehicle for

331

Bioactive Compounds in Food Nanotechnology. Food Hydrocolloid 2015, 51, 227-240.

332

(2) Wen, P.; Wen, Y.; Zong, M. H.; Linhardt, R. J.; Wu, H., Encapsulation of Bioactive Compound

333

in Electrospun Fibers and Its Potential Application. J. Agric. Food Chem. 2017, 65, 9161-9179.

334

(3) Bhushani, J. A.; Anandharamakrishnan, C., Electrospinning and Electrospraying Techniques:

335

Potential Food Based Applications. Trends Food Sci. Tech. 2014, 38, 21-33.

336

(4) Dong,

337

Superhydrophobic/Hydrophobic Surfaces Made from Amphiphiles through Droplet-Mediated

338

Evaporation-Induced Self-Assembly. J. Phys. Chem. B 2015, 119, 5321-5327.

339

(5) Wang, Y.; Chen, L., Fabrication and Characterization of Novel Assembled Prolamin Protein

340

Nanofabrics with Improved Stability, Mechanical Property and Release Profiles. J. Mater. Chem.

341

2012, 22, 21592-21601.

342

(6) Wang, X.; Ding, B.; Sun, G.; Wang, M.; Yu, J., Electro-Spinning/Netting: A Strategy for the

343

Fabrication of Three-Dimensional Polymer Nano-Fiber/Nets. Prog. Mater. Sci. 2013, 58,

344

1173-1243.

345

(7) Hualin, W.; Lilan, H.; Baicheng, N.; Suwei, J.; Junfeng, C.; Shaotong, J., Kinetics and

346

Antioxidant Capacity of Proanthocyanidins Encapsulated in Zein Electrospun Fibers by Cyclic

347

Voltammetry. J. Agric. Food Chem. 2016, 64, 3083-3090.

348

(8) Steyaert, I.; Rahier, H.; Vlierberghe, S. V.; Olijve, J.; Clerck, K. D., Gelatin Nanofibers:

349

Analysis of Triple Helix Dissociation Temperature and Cold-Water-Solubility. Food Hydrocolloid

350

2016, 57, 200-208.

351

(9) Taokaew, S.; Seetabhawang, S.; Siripong, P.; Phisalaphong, M., Biosynthesis and

F.; Zhang,

M.; Tang,

W.-W.; Wang,

Y.,

17


Formation and

Mechanism

of


352

Characterization of Nanocellulose-Gelatin Films. Mater. 2013, 6, 782-794.

353

(10) Kusumah, F. H.; Sriyanti, I.; Edikresnha, D.; Munir, M. M., Simply Electrospun

354

Gelatin/Cellulose Acetate Nnofibers and Their Physico-Chemical Characteristics. Mater. Sci. Forum

355

2017, 880, 95-98.

356

(11) Chang, S. T.; Chen, L. C.; Lin, S. B.; Chen, H. H., Nano-Biomaterials Application:

357

Morphology and Physical Properties of Bacterial Cellulose/Gelatin Composites Via Crosslinking.

358

Food Hydrocolloid 2012, 27, 137-144.

359

(12) Murtaza, G., Ethylcellulose Microparticles: A Review. Acta Pol. Pharm. 2012, 69, 11-22.

360

(13) Davidovich-Pinhas, M.; Co, E. D.; Barbut, S.; Marangoni, A. G., Physical Structure and

361

Thermal Behavior of Ethylcellulose. Cellulose 2015, 22, 2137-2137.

362

(14) Zhang, Z.; Zhang, H.; Zhang, Q.; Zhou, Q.; Zhang, H.; Mo, Z.; Zhao, X.; Wang, X.,

363

Thermotropic Liquid Crystallinity, Thermal Decomposition Behavior, and Aggregated Structure of

364

Poly(Propylene Carbonate)/Ethyl Cellulose Blends. J. Appl. Poly Sci. 2006, 100, 584-592.

365

(15) Lu, H. Y.; Wang, Q. Q.; Li, G. H.; Qiu, Y. Y.; Wei, Q. F., Electrospun Water-Stable Zein/Ethyl

366

Cellulose Composite Nanofiber and Its Drug Release Properties. Mater. Sci. Eng. C-Mater. Biol.

367

Appl. 2017, 74, 86-93.

368

(16) Swain, S. K.; Prusty, G.; Das, R., Sonochemical Compatibility of Polyvinyl

369

Alcohol/Polyacrylic Acid Blend in Aqueous Solution. J. Macromol. Sci. Part B-Phys. 2012, 51,

370

580-589.

371

(17) Chen, H. W.; Ma, Q.; Wang, S. D.; Liu, H.; Wang, K., Morphology, Compatibility, Physical

372

and Thermo-Regulated Properties of the Electrospinning Polyamide 6 and Polyethylene Glycol

373

Blended Nanofibers. J. Ind. Text. 2016, 45, 1490-1503. 18


Page 18 of 37

Page 19 of 37


374

(18) Wang, S. H.; Liu, J. H.; Pai, C. T.; Chen, C. W.; Chung, P. T.; Chiang, A. S. T.; Chang, S. J.,

375

Hansen Solubility Parameter Analysis on the Dispersion of Zirconia Nanocrystals. J. Colloid

376

Interface Sci. 2013, 407, 140-147.

377

(19) Miller, K. G.; Bowles, C. Q.; Chappelow, C. C.; Eick, J. D., Application of Solubility

378

Parameter Theory to Dentin-Bonding Systems and Adhesive Strength Correlations. J. Biomed.

379

Mater. Res. 1998, 41, 227-243.

380

(20) Ge, Z.; Xiao, C., Compatibility Studies with Blends Based on Poly(N‐Butyl Methacrylate)

381

and Polyacrylonitrile. J. Appl. Poly Sci. 2010, 115, 3357-3364.

382

(21) Yan, Q.; Zhao, T.; Bai, Y.; Zhang, F.; Yang, W., Precipitation Polymerization in Acetic Acid:

383

Study of the Solvent Effect on the Morphology of Poly(Divinylbenzene). J. Phys. Chem. B 2009,

384

113, 3008-14.

385

(22) Laha, A.; Yadav, S.; Majumdar, S.; Sharma, C. S., In-Vitro Release Study of Hydrophobic

386

Drug Using Electrospun Cross-Linked Gelatin Nanofibers. Biochem. Eng. J. 2016, 105, 481-488.

387

(23) Xiao, J.; Shi, C.; Zheng, H. J.; Shi, Z.; Jiang, D.; Li, Y. Q.; Huang, Q. R., Kafirin Protein Based

388

Electrospun Fibers with Tunable Mechanical Property, Wettability, and Release Profile. J. Agric.

389

Food Chem. 2016, 64, 3226-3233.

390

(24) Gomes, S.; Rodrigues, G.; Martins, G.; Henriques, C.; Silva, J. C., Evaluation of Nanofibrous

391

Scaffolds Obtained from Blends of Chitosan, Gelatin and Polycaprolactone for Skin Tissue

392

Engineering. Int. J. Biol. Macromol. 2017, 102, 1174-1185.

393

(25) Atila, D.; Keskin, D.; Tezcaner, A., Crosslinked Pullulan/Cellulose Acetate Fibrous Scaffolds

394

for Bone Tissue Engineering. Mater. Sci. Eng., C 2016, 69, 1103-1115.

395

(26) Vatankhah, E.; Prabhakaran, M. P.; Jin, G.; Mobarakeh, L. G.; Ramakrishna, S., Development 19



396

of Nanofibrous Cellulose Acetate/Gelatin Skin Substitutes for Variety Wound Treatment

397

Applications. J. Biomater. Appl. 2014, 28, 909-921.

398

(27) Gravelle, A. J.; Davidovich-Pinhas, M.; Zetzl, A. K.; Barbut, S.; Marangoni, A. G., Influence

399

of Solvent Quality on the Mechanical Strength of Ethylcellulose Oleogels. Carbohydr. Polym. 2016,

400

135, 169-179.

401

(28) Peyches-Bach, A.; Dombre, C.; Moutounet, M.; Peyron, S.; Chalier, P., Effect of Ethanol on the

402

Sorption of Four Targeted Wine Volatile Compounds in a Polyethylene Film. J. Agric. Food Chem.

403

2012, 60, 6772-6781.

404

(29) Stortz, T. A.; Marangoni, A. G., The Replacement for Petrolatum: Thixotropic Ethylcellulose

405

Oleogels in Triglyceride Oils. Green Chem. 2014, 16, 3064-3070.

406

(30) Gravelle, A. J.; Davidovich-Pinhas, M.; Zetzl, A. K.; Barbut, S.; Marangoni, A. G., Influence

407

of Solvent Quality on the Mechanical Strength of Ethylcellulose Oleogels. Carbohydr. Polym. 2015,

408

135, 169.

409

(31) Shenoy, S. L.; Bates, W. D.; Wnek, G., Correlations between Electrospinnability and Physical

410

Gelation. Polym. 2005, 46, 8990-9004.

411

(32) Yoon, K.; Kim, K.; Wang, X.; Fang, D.; Hsiao, B. S.; Chu, B., High Flux Ultrafiltration

412

Membranes Based on Electrospun Nanofibrous Pan Scaffolds and Chitosan Coating. Polym. 2006,

413

47, 2434-2441.

414

(33) Zhong, S.; Zhang, Y.; Lim, C. T., Fabrication of Large Pores in Electrospun Nanofibrous

415

Scaffolds for Cellular Infiltration: A Review. Tissue Eng. Part B-Rev. 2012, 18, 77-87.

416

(34) Veleirinho, B.; Lopesdasilva, J. A., Application of Electrospun Poly(Ethylene Terephthalate)

417

Nanofiber Mat to Apple Juice Clarification. Process Biochem. 2009, 44, 353-356. 20


Page 20 of 37

Page 21 of 37


418

(35) Chiellini, E.; Cinelli, P.; Grillo, F. E.; Elrs, K.; Lazzeri, A., Gelatin-Based Blends and

419

Composites. Morphological and Thermal Mechanical Characterization. Biomacromolecule 2001, 2,

420

806-11.

421

(36) Mu, C.; Guo, J.; Li, X.; Lin, W.; Li, D., Preparation and Properties of Dialdehyde

422

Carboxymethyl Cellulose Crosslinked Gelatin Edible Films. Food Hydrocolloid 2012, 27, 22-29.

423

(37) Dafader, N. C.; Rahman, S. T.; Rahman, W.; Rahman, N.; Manir, M. S.; Alam, M. F.; Alam, J.;

424

Sumi, S. A., Preparation of Gelatin/Poly(Vinyl Alcohol) Film Modified by Methyl Methacrylate and

425

Gamma Irradiation. Int. J. Polym. Anal. Charact. 2016, 21, 513-523.

426

(38) Jiang, Y. C.; Lin, J.; An, H.; Wang, X. F.; Qian, L.; Turng, L. S., Electrospun

427

Polycaprolactone/Gelatin Composites with Enhanced Cell–Matrix Interactions as Blood Vessel

428

Endothelial Layer Scaffolds. Mater. Sci. Eng., B 2017, 71, 901-908.

429

(39) Ki, C. S.; Baek, D. H.; Gang, K. D.; Lee, K. H.; Um, I. C.; Park, Y. H., Characterization of

430

Gelatin Nanofiber Prepared from Gelatin–Formic Acid Solution. Polym. 2005, 46, 5094-5102.

431

(40) Sinthusamran, S.; Benjakul, S.; Kishimura, H., Characteristics and Gel Properties of Gelatin

432

from Skin of Seabass (Lates Calcarifer) as Influenced by Extraction Conditions. Food Chem. 2014,

433

152, 276-284.

434

(41) Desai, J.; Alexander, K.; Riga, A., Characterization of Polymeric Dispersions of

435

Dimenhydrinate in Ethyl Cellulose for Controlled Release. Int J Pharm 2006, 308, 115-23.

436

(42) Zhang, Y. Z.; Venugopal, J.; Huang, Z. M.; Lim, C. T.; Ramakrishna, S., Crosslinking of the

437

Electrospun Gelatin Nanofibers. Polym. 2006, 47, 2911-2917.

438

(43) Soradech, S.; Nunthanid, J.; Limmatvapirat, S.; Luangtanaanan, M., An Approach for the

439

Enhancement of the Mechanical Properties and Film Coating Efficiency of Shellac by the 21



440

Formation of Composite Films Based on Shellac and Gelatin. J. Food Eng. 2012, 108, 94-102.

441

(44) Huang, L.; Arena, J. T.; Manickam, S. S.; Jiang, X.; Willis, B. G.; Mccutcheon, J. R., Improved

442

Mechanical Properties and Hydrophilicity of Electrospun Nanofiber Membranes for Filtration

443

Applications by Dopamine Modification. J. Membrane. Sci. 2014, 460, 241-249.

444

(45) Dutta, P. K.; Tripathi, S.; Mehrotra, G. K.; Dutta, J., Perspectives for Chitosan Based

445

Antimicrobial Films in Food Applications. Food Chem. 2009, 114, 1173-1182.

446 447

22


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448

Figure captions

449

Figure 1 SEM images and the diameter distribution of the electrospun ethylcellulose/gelatin

450

nanofibers at weight ratios of 0/1, 1/3, 1/1, 3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and

451

EG10, respectively). Lowercases indicated statistical significance (p < 0.05).

452 453

Figure 2 Porosity of the electrospun ethylcellulose/gelatin nanofibers at weight ratios of 0/1, 1/3,

454

1/1, 3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and EG10, respectively). Lowercases

455

indicated statistical significance (p < 0.05).

456 457

Figure 3 TGA (A) and DSC (B) curves of the electrospun ethylcellulose/gelatin nanofibers at

458

weight ratios of 0/1, 1/3, 1/1, 3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and EG10,

459

respectively).

460 461

Figure 4 FTIR spectra of the electrospun ethylcellulose/gelatin nanofibers at weight ratios of 0/1,

462

1/3, 1/1, 3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and EG10, respectively).

463 464

Figure 5 Water contact angles of the electrospun ethylcellulose/gelatin nanofibers at weight ratios

465

of 0/1, 1/3, 1/1, 3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and EG10, respectively).

466 467

Figure 6 Water evapotation of the electrospun ethylcellulose/gelatin nanofibers at weight ratios of

468

0/1, 1/3, 1/1, 3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and EG10, respectively).

469

23



470

Figure 7 SEM images of the electrospun ethylcellulose/gelatin nanofibers at weight ratios of 0/1

471

(A), 1/3 (B), 1/1 (C), 3/1 (D) and 1/0 (E) (denoted as EG01, EG13, EG11, EG31 and EG10,

472

respectively). (F) The gelatin weight loss profiles of the nanofibers after immersed in water for 10

473

days.

474

24


Page 24 of 37

Page 25 of 37


475

Tables

476

Table 1 (A). The reported Hansen solubility parameters (in MPa0.5) of polymers and solvents.

a

477

a

Literature values

δd

δp

δh

δt

Ethylcellulose29

16.6

8.3

9.7

20.9

Gelatin19

16.0

20.3

23.6

35.0

Water28

15.5

16.0

42.3

47.8

Ethanol28

15.8

8.8

19.4

26.5

Acetic acid21

14.6

7.9

15.2

22.5

Water/Ethanol/Acetic acid (2/2/6, v/v/v)

15.0

6.5

21.5

30.0

Here, δmix= Φ1·δh1 + Φ2·δh2, Φ represents the volume ratio of each solvent in solution.

478

25



Page 26 of 37

479

Table 1 (B). The calculated difference in Hansen solubility parameters (in MPa0.5) and the apparent

480

viscosity at shear rate of 1 s-1 of the ethylcellulose/gelatin solutions at weight ratios of 0/1, 1/3, 1/1,

481

3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and EG10, respectively). Polymer-solvent

Ethanol/acetic acid/water (2/6/2,v/v/v) a

Apparent viscosityb

Ra

(Pa·s)

2.1

14.1

2.51 ± 0.06 e

10.8

1.4

11.1

6.74 ± 0.34 c

1.3

7.8

4.8

9.6

5.24 ± 0.11 d

EG31

1.5

4.8

8.3

9.9

13.40 ± 0.55 a

EG10

1.6

1.8

11.8

12.2

8.53 ± 0.10 b

compatibility

δd

δp

δh

EG01

1.0

13.8

EG13

1.2

EG11

482

a

Here, (Ra)2= 4·(δd2-δd1)2 + (δp2-δp1)2 + (δh2-δh1)2.

483

b

Lowercases in the column indicated statistical significance (p < 0.05).

484

26


Page 27 of 37


485

Table 2 (A). The weight loss rate (Mr) and maximum degradation temperature (Tdm) of TGA curves

486

of the electrospun ethylcellulose/gelatin nanofibers at weight ratios of 0/1, 1/3, 1/1, 3/1 and 1/0

487

(denoted as EG01, EG13, EG11, EG31 and EG10, respectively). Part I (0 - 160 °C)

Part II (160 - 380 °C)

Part III (380 - 600 °C)

Samples

488

a

Mr (%)

Tdm (°C)

Mr (%)

Tdm (°C)

Mr (%)

Tdm (°C)

EG01

2.24

63.65

57.93

311.82

12.77

-a

EG13

1.29

62.37

37.22

353.01

6.66

-

EG11

1.09

60.42

68.29

355.16

8.48

-

EG31

0.26

-

84.38

352.41

4.13

-

EG10

0.09

-

93.09

349.18

1.47

-

Not available.

489

27



Page 28 of 37

490

Table 2 (B). The transition temperature (Tm), enthalpy (Hm) and glass transition temperature (Tg) in

491

DSC curves of the electrospun ethylcellulose/gelatin nanofibers at weight ratios of 0/1, 1/3, 1/1, 3/1

492

and 1/0 (denoted as EG01, EG13, EG11, EG31 and EG10, respectively).

493

a

Samples

Tm1 (°C)

Hm1 (J/g)

Tm2 (°C)

Hm2 (J/g)

Tm3 (°C)

Hm3 (J/g)

Tg

EG01

60.31

6.13

121.47

189.0

213.34

12.98

-a

EG13

61.13

4.62

127.22

174.4

215.65

6.63

-

EG11

66.10

3.31

112.40

98.37

218.35

3.79

-

EG31

63.31

2.00

107.70

64.03

217.18

1.80

-

EG10

-

-

65.73

25.51

190.95

2.42

123.47

Not available.

494

28


Page 29 of 37


495

Table 3. The surface swelling, water uptake and weight loss of the electrospun ethylcellulose/gelatin

496

nanofibers at weight ratios of 0/1, 1/3, 1/1, 3/1 and 1/0 (denoted as EG01, EG13, EG11, EG31 and

497

EG10, respectively), after immersed in water for 10 days.

498 499 500

Samples

Surface swelling (%)

Water uptake (%)

Weight loss (%)

EG01

-a

-

-

EG13

-37.11 ± 0.75 a

1234.14 ± 256.49 a

21.60 ± 1.02 a

EG11

-30.60 ± 4.12 b

832.36 ± 66.61 ab

11.45 ± 0.76 b

EG31

-21.13 ± 1.56 c

393.07 ± 28.29 c

2.58 ± 0.14 c

EG10

-27.37 ± 3.06 b

550.75 ± 20.93 bc

3.35 ± 0.43 c

a

The pure gelatin nanofibers were completely dissolved in water.

b

Lowercases indicated statistical significance (p < 0.05) within each column.

29



Figure 1

30


Page 30 of 37

Page 31 of 37


Figure 2

31



Figure 3

501

32


Page 32 of 37

Page 33 of 37


Figure 4

33



Figure 5

34


Page 34 of 37

Page 35 of 37


Figure 6

35



Figure 7

502

36


Page 36 of 37

Page 37 of 37

503


Abstract graphic

37


Gelatin Composite

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