Natural Flavonoid-Functionalized Silk Fiber Presenting Antibacterial

Subscriber access provided by Eastern Michigan University | Bruce T. Halle Library

Article

Natural Flavonoid-Functionalized Silk Fiber Presenting Antibacterial, Antioxidant, and UV Protection Performance Yuyang Zhou, and Ren-Cheng Tang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b02513 • Publication Date (Web): 12 Oct 2017 Downloaded from http://pubs.acs.org on October 17, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Sustainable Chemistry & Engineering is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Natural Flavonoid-Functionalized Silk Fiber Presenting Antibacterial, Antioxidant, and UV Protection Performance

Yuyang Zhou, Ren-Cheng Tang*

National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, 199 Renai Road, Suzhou 215123, China

*

Corresponding author:

E-mail address: [email protected] Tel: +86 512 6716 4993. Fax: +86 512 6724 6786.

1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT: Natural bioactive compounds as promising alternatives to synthetic finishing agents have recently gained increasing attention in textile industry due to their eco-friendliness, low irritation, and biocompatibility. The present study reports a sustainable approach for preparing antibacterial, antioxidant, and UV-protective silk fiber using two natural flavonoids (quercetin and rutin) by an adsorption technique. The adsorption kinetics and isotherms of the two flavonoids were investigated, and their functionalities and the washing durability of their functionalities were discussed. The equilibrium adsorption isotherms fitted well to the Langmuir and Freundlich adsorption models, demonstrating that ion-ion interactions, hydrogen bonding, and van der Waals forces play major roles in the adsorption of quercetin and rutin on silk. The adsorption isotherm parameters of quercetin and rutin had a decisive effect on their adsorption kinetics which fitted well to the pseudo second-order kinetic equation. Quercetin exhibited higher initial adsorption rate, shorter half adsorption time, and higher adsorption capability than rutin due to its higher affinity constant. Quercetin also imparted better antioxidant, antibacterial and UV protection performance to silk than rutin at the same initial application concentration, and provided better washing durability of functionalities. This study demonstrates that quercetin and rutin can be employed as promising multifunctional agents for the chemical processing of silk materials. KEYWORDS: flavonoids, adsorption, silk, antibacterial activity, antioxidant activity, UV protection

2


Page 2 of 35

Page 3 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


INTRODUCTION With the enhancement of environmental consciousness, the bioactive extracts from plants as the renewable and sustainable bioresource products, have drawn more and more attention in textile industry owing to their non-toxicity, degradability, and eco-friendliness.1 Many studies have also confirmed that natural bioactive extracts possess a diversity of functionalities such as antibacterial activity, antioxidant activity, anti-inflammatory activity, etc., which have a promising prospect in the development of hygiene-related and medical textiles.2,3 In addition, the application of natural functional colors in textiles combines dyeing and finishing processes,4 which can be regarded as an efficient technique with low consumption of water and energy. Silk, because of its several outstanding properties including smooth and lustrous appearance, soft handle, hygroscopicity, and wearing comfortableness, has been regarded as luxurious textiles for thousands of years. Furthermore, the superior mechanical performance and bioavailability of silk enable it to be an appropriate material which can be applied as biomedical textiles, scaffolds for tissue engineering, surgical threads, and wound dressings.5 However, several obvious drawbacks of silk fiber, for instance, low antimicrobial and antioxidant activity, poor UV protection ability, and deterioration, greatly impede its practical applications.5,6 Thus, efforts should be made to overcome these deficiencies, and to provide silk with specific functionalities. In recent investigations, the antibacterial functionalization of silk by inorganic nanomaterials and natural bioactive extracts has become a hot issue.1–8 Flavonoids, accounting for the largest proportion in the family of natural bioactive

3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

extracts, are known to be produced by plants in order to defense against microbial invasions. Moreover, flavonoids have already been found to have potent antioxidant activity for decades, which are able to reduce the amount of active and harmful substances such as reactive oxygen free radicals through radical scavenging.9 In recent years, a small amount of available literature has been focused on the functionalization of textiles by flavonoids, and the interactions between flavonoids and fiber materials.6,10,11 Altıok et al.10 innovatively adopted silk fibroin as an adsorbent for the recycle of the polyphenols including several flavonoids from the extracts of olive leaf, indicating the occurrence of the interactions between silk and flavonoids. Flavonoids were ascertained to be efficient in improving the UV protection ability of cellulosic fabrics.11 In our previous work,6 baicalin which has one carboxyl group but no catechol moiety in B-ring was successfully used to impart antibacterial, antioxidant, and UV protection functions to silk fiber, and the electrostatic interaction operating between the carboxyl group of baicalin and the amino group of silk was clarified. Quercetin and rutin (Figure 1) belong to the bioactive flavonoid compounds, existing widely in different sorts of fruits and vegetable tissues.12,13 In fact, the critical difference between their chemical structures is that rutin contains one disaccharide moiety at the C-3 position of C-ring. It is widely known that glycosyl groups are very common in flavonoids and have been found to be responsible for the hydrophilicity and biological properties.14–17 So far, few reports have focused on the fabrication of multifunctional silk with flavonoids with different chemical structures. Furthermore, the relationships among the adsorption behaviors of flavonoids, the functions of silk imparted by

4


Page 4 of 35

Page 5 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


flavonoids, and the chemical structures of flavonoids also remain to be explored.

Figure 1. Chemical structures of quercetin and rutin.

Both quercetin and rutin are faintly colored flavonoids, thus they are very appropriate for the functional modification of silk due to the fact that they probably exert little influence on the color of silk materials. The aim of the present research was to prepare the bioactive and UV protective silk materials by the introduction of querectin and rutin. In the present work, the pH dependence of the uptake of quercetin and rutin by silk was explored, the adsorption mechanism and capability of quercetin and rutin on silk were discussed, and the antioxidant activity, antibacterial activity and UV protection ability of the silk treated with quercetin and rutin were determined. The relations among the structures, adsorption mechanism and capability, and functions of quercetin and rutin were emphasized.

EXPERIMENTAL SECTION Materials. The silk fabric of crepe de chine (specification code: 12103) was purchased from Suzhou Jiaduoli Silk Apparel Co. Ltd., China. Quercetin (purity 95%) and rutin (purity 95%) were obtained from Xi'an Qing Yue Biotechnology Co. Ltd.,

5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

China. 2,2’-Azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), citric acid, disodium hydrogen phosphate, monopotassium phosphate, and potassium peroxodisulfate were analytical grade reagents. A commercial detergent specially used for the laundering of silk was provided by Shanghai Zhengzhang Laundering and Dyeing Co. Ltd., China. Nutrient agar and nutrient broth were used in the antibacterial test, and bought from Sinopharm Chemical Reagent Co. Ltd., China and Shanghai Sincere Biotech Co. Ltd., China, respectively. Adsorption of Quercetin and Rutin. All the treatment processes were implemented in the conical flasks which were shaken in an oscillated dyeing machine. A liquor ratio (liquor volume to fabric weight) of 50:1 was used. Citric acid-disodium hydrogen phosphate buffer was used for the adjustment of pH values. At the end of each treatment, the treated fabrics were rinsed by distilled water and then allowed to dry in the open air. PH Dependence of Adsorption. In this section, 3% owf (on the weight of fabric) quercetin and rutin were used in the silk treatment with a pH range from 2.7 to 7.1. The temperature of the treatment bath was raised from 30 to 90 oC at a rate of 2 oC/min, and the treatment was carried out at 90 oC for 60 min. Adsorption Kinetics. The solutions containing 3% owf quercetin or rutin were used, and their pH values were adjusted to 2.75. The fabrics were treated at 90 oC for different times. Equilibrium Adsorption Isotherms. The explorations of adsorption isotherms for quercetin and rutin on silk were conducted at pH 2.75 and 90 oC using a series of flavonoid concentrations from 1 to 10% owf. According to the study of adsorption

6


Page 6 of 35

Page 7 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


kinetics, the adsorption reached to an equilibrium state in 90 min. Thus, the fabrics were treated for 90 min in this section. Building-Up Properties. A series of of quercetin and rutin concentrations (1–10% owf) were used. The pH values of the solutions were adjusted to 2.75. The temperature of the treatment bath was raised from 30 to 90 oC at a rate of 2 oC/min, and the treatment continued at 90 oC for 60 min. The as-prepared samples were employed for the evaluation of functionalities. Measurements. Uptake of Quercetin and Rutin by Silk. The UV/Vis absorption spectra were obtained by a Shimadzu UV-1800 UV/Vis spectrophotometer (Shimadzu Co., Japan). Taking the low solubility of quercetin and rutin into account, their solutions were diluted 50 times with 80% ethanol prior to the measurement. The determination of exhaustion percentage of quercetin (λmax=364 nm) and rutin (λmax=351 nm) was based on the previously established standard working curves according to Equation (1), where C0 and C1 are the concentrations of quercetin and rutin before and after adsorption, respectively. The concentrations of quercetin and rutin on silk were determined according to the difference in the concentrations of quercetin and rutin in solution before and after adsorption, and the weight of the dried fabric. Exhaustion (%) =

C0 − C1 ×100 C0

(1)

Color Characteristics. The color parameters of each sample which was folded twice were measured by a Datacolor 600 (Datacolor Technology Co., USA) using D65 illumination and 10° observer. The lightness [L*], redness-greenness value [a*], and yellowness-blueness value [b*] were recorded. The color difference (DE) was 7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 35

determined by Equation (2), where the subscripts ‘untr’ and ‘tr’ represent the silk fabrics untreated and treated with quercetin or rutin, respectively. 1/2

2 2 2 * * DE = ( L*tr − L*untr ) + ( a *tr − auntr ) + ( btr* − buntr )  

(2)

Antioxidant Activity. The antioxidant property of samples was determined by the ABTS radical decolorization assay using spectrophotometric analysis according to the previous method.18 More details regarding the antioxidant activity assessment were shown in our previous work.4,6 Antibacterial Activity. The antibacterial activity of samples was assessed according to GB/T 20944.3-2008. Escherichia coli (E. coli, ATCC 8099) and Staphylococcus aureus (S. aureus, ATCC 6538) were provided by College of Life Science, Soochow University (China). More details regarding the antibacterial activity assessment were shown in our previous work.4,6 UV Protection Performance. The UV transmittance and UV protection factor (UPF) of samples were determined in a Labsphere UV-1000F UV transmittance analyzer (Labsphere Inc., USA) according to GB/T 18830-2009. Four different positions of each sample were measured in order to give an average result. Durability of Functionalities. The functionalities of the silk fabrics subjected to 1, 5 and 10 washing cycles were evaluated. The washing was carried out at 40 oC according to our previously reported method.19 Test of the desorption of flavonoids from the treated silk. The desorption of flavonoids from the treated silk in water was investigated at 30 oC. The liquor ratio was adjusted to 200:1. The silk fabrics treated with 3% owf flavonoids according to the method

8


Page 9 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


described in the section of Building-Up Properties were used in the test. The change of the desorption rate over time was determined by the difference in the concentrations of flavonoids on silk before and after desorption. Surface morphology, thermal stability and mechanical performance. The untreated silk and 2% owf flavonoids treated silk obtained in the section of Building-Up Properties were used for the investigation of surface morphology, thermal stability and mechanical performance. The surface morphologies of silk fabrics were observed using a TM3030 tabletop scanning electron microscope (Hitachi High Technologies America Inc., USA). The thermal stability of the fabrics was studied using a TG/DTA 6300 (Seiko Instruments, Inc., Japan) from 50 to 600 oC with a heating rate of 10 oC/min in nitrogen (20 mL/min). The tensile strength of the samples was tested by an Instron 3365 tester (Illinois Tool Works Inc., UK) according to ISO 13934-1: 2013. Prior to the measurement, all the samples were conditioned in a standard atmospheric condition for 24 h. Finally, the average results of six specimens were reported for each sample.

RESULTS AND DISCUSSION UV–Vis Absorption Spectroscopy. The UV–Vis absorption spectroscopy of quercetin and rutin provides an amount of details about their water solubility, stability, and spectral features, which are in close relationship with their application properties. Moreover, the multiple hydroxyl groups of flavonoid compounds are inclined to ionize or to be oxidized at different pH values, leading to the variation in the physical and chemical behaviors of flavonoids.20,21 Therefore, it is essential to study the UV–Vis

9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

absorption spectra of quercetin and rutin at different pH values before their application to silk. As seen in Figure 2, quercetin showed very low absorption intensity below pH 7 and the deposition of the particles were found at the container bottom, indicating its low solubility. The absorption intensity of rutin was higher than that of quercetin at pH 7, which manifests that rutin has better solubility than quercetin as a result of the presence of hydrophilic glycosidic moiety in its chemical structure.17,22 When the pH value increased above pH 7, the absorbance of quercetin and rutin solutions became higher, less deposition was observed at the bottom of the container and the color of the solution also changed. These phenomena are associated with the deprotonation of hydroxyl groups in their structures both at 7 and 4’ positions.23–25 Additionally, two major absorption bands (Bands I and II) were observed in the UV–Vis absorption spectra of quercetin and rutin.26 Band I in the 300–400 nm range represents the absorption of the cinnamoyl system (B- and C-rings), whereas Band II in the 240–280 nm range is attributed to the benzoyl system (A- and C-rings). When pH increased to 9, a new peak at a longer wavelength (about 395 nm) appeared. Then the new peak underwent a red shift as the pH further increased. These complex variations in basic condition indicate that the species at high pH are not just a consequence of the deprotonation of hydroxyl groups in flavonoids.27 Taking the unstability of flavonoids in basic condition into consideration, quercetin and rutin were applied in acidic conditions in the following experiments.

10


Page 10 of 35

Page 11 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. UV–Vis absorption spectra of quercetin (a) and rutin (b) in water at different pH values (Concentration: 0.01 g/L).

Adsorption Properties. PH Dependence of Adsorption. The pH value can significantly influence the uptake of flavonoids by silk, owing to the fact that the pH can change the ionization extent of flavonoids and the net charge of silk fiber. In addition, the pH value of solution can also lead to the color changes of quercetin and rutin according to the aforementioned results. As shown in Figure 3a, the uptake of quercetin by silk had almost no change in the pH range of 2.8 to 5.1, and then dropped down dramatically. Additionally, quercetin

11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

showed much better adsorption capacity on silk than rutin, which can be explained by the fact that rutin has better water solubility than quercetin as it contains the hydrophilic glycosidic moiety, leading to its great tendency towards distribution in water.

Figure 3. PH dependence of the uptake of quercetin and rutin by silk (a), and the color characteristics of the treated silk (b).

The color variations of silk fabrics induced by treatment of quercetin and rutin in a pH range of 2.75–7.08 are depicted in Figure 3b. The silk fabrics treated with quercetin displayed more yellow appearance with high b* values than those treated with rutin. However, the silk fabrics treated with rutin at different pH values displayed marginal

12


Page 12 of 35

Page 13 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


color variations. These phenomena are consistent with the color changes of quercetin and rutin in water (Figure 2). Considering the high utilization of quercetin and rutin, pH 2.75 was used in the following studies. Adsorption Kinetics. The adsorption kinetics which plays a significant role during the treatment process can provide very useful information in the design of adsorption systems. In this work, the adsorption rates of quercetin and rutin were investigated in terms of their adsorption amount (Ct) as a function of time (t). As depicted in Figure 4, the adsorption quantity of quercetin and rutin showed a dramatic increase in the first 30 min. Moreover, quercetin showed a higher adsorption rate than rutin. After approximately 90 min, the adsorption quantity of quercetin and rutin onto silk became constant, indicating that the adsorption equilibrium was reached.

Figure 4. Adsorption rates of quercetin and rutin for silk.

In order to obtain the parameters of adsorption kinetics, the pseudo second-order kinetic equation was used to fit the experiment data. Equation (3) represents the pseudo second-order kinetic equation,28 where k is the adsorption rate constant, and Ct and Ce

13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 35

are the adsorption quantities of flavonoids at time t and at equilibrium, respectively. t 1 1 = + t 2 Ct kCe Ce

(3)

If the adsorption complies with the pseudo second-order kinetic equation, t/Ct would have a linear relation with t. The slope and intercept of the relative linear regression line were employed to calculate the k and Ce values. In addition, the half adsorption time (t1/2) as well as the initial adsorption rate (ri) was calculated according to Equations (4) and (5), respectively. t1/ 2 =

1 kCe

(4)

ri = kCe2

(5)

The correlation coefficients (R2) of the kinetic model are listed in Table 1. Clearly, the R2 values for the linear plots of quercetin and rutin were very high, proving the validity of the pseudo-second-order kinetic equation in describing the adsorption process of quercetin and rutin. Quercetin exhibited higher initial adsorption rate, shorter half adsorption time, and slightly higher adsorption rate constant than rutin. Moreover, quercetin exhibited remarkably higher equilibrium adsorption quantity than rutin. All these results indicate that the affinity of quercetin to silk is higher than that of rutin, which enables us to further explore the equilibrium adsorption behaviors of quercetin and rutin onto silk.

14


Page 15 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1. Adsorption Kinetic Parameters of Quercetin and Rutin for Silk. ri

t1/2

k

Ce

(mg/[g·min])

(min)

(10-3 g/[mg·min])

(mg/g)

R2

Samples

Quercetin

4.57

5.68

6.8

25.97

0.9998

Rutin

0.60

16.16

6.4

9.65

0.9992

Adsorption Isotherms. The equilibrium adsorption isotherms are fundamental in describing the interactions between flavonoids and silk fiber, which can provide the most important information for analyzing and designing the adsorption process. The adsorption isotherms of quercetin and rutin on silk at pH 2.75 are depicted in Figure 5.

Figure 5. Equilibrium adsorption isotherms of quercetin and rutin for silk.

Langmuir and Freundlich adsorption models were used to describe the experimental isotherm points. For the Langmuir adsorption model, it is assumed that once one solute molecule is adsorbed by one reactive site of adsorbent, further adsorption at this site is impossible. In theory, when all reactive sites of adsorbent are occupied by solute

15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 35

molecules, no further adsorption can occur. The Langmuir isotherm has a pronounced plateau of the complete monolayer fulfillment, which is quite common in chemisorption processes. The expression of Langmuir adsorption is shown in Equation (6), where Cf (mg/g) and Cs (mg/L) represent the concentration of quercetin or rutin on silk and in solution at equilibrium, respectively; S is the saturation concentration of quercetin or rutin on silk; KL is the Langmuir affinity constant. Cf =

SK L Cs 1 + SK L Cs

(6)

The Freundlich isotherm is also a widely accepted adsorption model. This model describes the equilibrium adsorption of solute on the heterogeneous surfaces of adsorbent, and thus does not assume a monolayer capacity.29 The Freundlich equation is given as Equation (7), where KF is the Freundlich affinity constant, and n is an indicator of surface heterogeneity or adsorption intensity.

Cf = K FCsn

(7)

The Langmuir and Freundlich adsorption parameters were obtained from the linear plots of 1/Cf versus 1/Cs and lnCf versus lnCs, respectively and listed in Table 2. From Table 2, it is clear that the Langmuir equation fitted quite well with the experimental points (R2=0.9961 for quercetin, and R2=0.9998 for rutin), whereas the Freundlich equation displayed slightly lower correlation coefficients (R2 =0.9911 for quercetin,

R2=0.9974 for rutin). This indicates that the Langmuir adsorption mechanism is more favorable than the Freundlich adsorption mechanium. On the other hand, the Freundlich exponent n was very close to 1, indicating that the reactive sites of silk fiber available for the adsorption of quercetin and rutin have a high degree of homogeneity. These 16


Page 17 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


results indicate the significant contribution of chemisorption process in a monolayer followed by a multilayer physisorption.

Table 2. Langmuir and Freundlich Adsorption Parameters of Quercetin and Rutin for Silk. Langmuir

Freundlich

Samples

KL (L/g)

S (mg/g)

R2

KF (L/g)

n

R2

Quercetin

0.684

212.77

0.9961

0.130

1.05

0.9911

Rutin

0.268

72.46

0.9998

0.036

0.88

0.9974

Our previous work showed that silk fiber has an isoelectric point of 4.32.6 Therefore, silk fiber is positively charged at pH 2.75 which was used in this study, owing to the protonation of amino groups in its structure. The ion-ion interactions of the positively charged silk fiber with the deprotonated phenolic hydroxyl groups in quercetin and rutin can contribute to the Langmuir adsorption. The dissociation constants (pKa1) of quercetin and rutin reported in the literature are 5.87 and 7.1, respectively.23,30 At these pH values, the ionized fraction of phenolic hydroxyl groups is 50%. Thus, in the adsorption process, as a small quantity of hydroxyl groups in quercetin and rutin molecules are subjected to deprotonation at the pH used, and adsorbed by the positively charged silk fiber, their dynamic ionization equilibrium is broken which can promote the further disassociation and adsorption of quercetin and rutin. Additionally, quercetin and rutin have multiple hydrogen groups, and silk fiber bears a large amount of amide, amino, and carboxyl groups. Thus, hydrogen bonding can occur between silk fiber and

17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

quercetin and rutin. There also exist van der Waals forces between silk and quercetin and rutin, which contribute to the Freundlich adsorption. As far as the adsorption parameters were concerned, quercetin showed higher Langmuir affinity constant (KL), Freundlich affinity constant (KF), and adsorption saturation (S) than rutin. The high KL and KF values reveal that quercetin has a high affinity to silk fiber than rutin, which agrees well with the results of the adsorption kinetics mentioned above.

Building-Up Property. The building-up ability of plant extracts have received particular attention in textile industry owing to its close relationship with the utilization and eco-environmental impacts, which is related to the chemical structure, affinity to fiber, and adsorption mechanism and capability of natural substances. Thus, the building-up ability of quercetin and rutin on silk were also explored. As shown in Figure 6a, the adsorption amount of quercetin on silk continued to increase as its initial concentration increased, and the exhaustion percentage was still above 60% even at the initial concentration of 6% owf, indicating its good building-up capability and high utilization. However, rutin displayed much lower exhaustion and adsorption quantity than quercetin. The poor building-up ability of rutin would mean a high application cost. As quercetin and rutin are pale yellow in color, their treatment can exert certain impacts on the appearance of silk. As shown in Figure 6b, the treated silk fabrics displayed increasing b* values and color difference (DE in the inserted table) along with increasing concentrations of quercetin and rutin. Compared with the untreated silk, the

18


Page 18 of 35

Page 19 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


treated samples showed a palely brilliant yellow appearance. Quite evidently, rutin had a smaller effect on the color of silk than quercetin.

Figure 6. Exhaustion and adsorption quantity of quercetin and rutin on silk at various concentrations (a), and color characteristics of the treated silk fabrics (b).

Functionalities. Antioxidant Activity. Previous studies have reported that the catechol moiety in B-ring, the 3-hydroxyl group in C-ring, and the hydroxyl groups in A-ring contribute to the antioxidant action of flavonoids.31 Generally, quercetin exhibits higher antioxidant activity than rutin in vitro as it bears the free 3-hydroxyl group in C ring, and the greater number of hydroxyl groups.17 For the treated silk fabrics, their

19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 35

antioxidant activity depends not only on the molecular structures of flavonoids, but also on the adsorption quantities of flavonoids. As seen in Figure 7a, the original silk exhibited poor antioxidant activity when compared to the quercetin and rutin treated silk. The silk samples treated with quercetin •

and rutin showed remarkable antioxidant activity. The color of ABTS + faded away in a few minutes after the contact with the treated samples, indicating that the treated silk possessed high-efficient radical scavenging ability. The antioxidant activity of silk treated with 2% owf quercetin and rutin reached 99% and 82%, respectively, suggesting that a small quantity of quercetin and rutin can endow silk with excellent antioxidant activity. At the same initial concentration, quercetin can endow silk with higher antioxidant activity than rutin, mainly due to its higher adsorption capability on silk as mentioned above. Figure 7b is a further plot of Figure 7a, which reflects the relationship between the antioxidant activity of the treated silk and the adsorption quantity of flavonoids on silk. Clearly, the antioxidant activity increased with increasing adsorption quantity of flavonoids. It is interesting to note that the rutin treated silk was more effective in free radical scavenging than the quercetin treated silk at almost the same adsorption quantity. To be specific, rutin showed an antioxidant value of 99.21% at the adsorption quantity of 8.81 mg/g, whereas the antioxidant activity of quercetin was 93.21% at the adsorption quantity of 8.46 mg/g. This phenomenon can be attributable to the fact that rutin is more easily desorbed from the treated silk in the ABTS˙+ solution than quercetin due to its low affinity to silk and relatively high hydrophilicity.

20


Page 21 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. Correlation of the antioxidant activity of the treated silk with the initial application concentration (a) and adsorption quantity (b) of quercetin and rutin.

Antibacterial Activity. The antibacterial activity of quercetin and rutin in vitro has been reported to be achieved via molecular actions by forming complex with proteins through nonspecific forces.32 In the present work, the antibacterial activities of the silk samples treated with 2% and 8% owf quercetin and rutin against E. coli and S. aureus were checked, and the results are depicted in Figure 8. The original silk fabric had poor antibacterial activity, and its reduction rate against E.

coli and S. aureus was of 15% and 17%, respectively, whereas the treated silk presented significantly enhanced antibacterial performance which increased with an increase in the initial concentration of quercetin and rutin (Figure 8a). Moreover, the quercetin treated silk showed higher antibacterial activity than the rutin treated silk at the same initial application concentration. In the frame diagram of Figure 8b, a further plot of Figure 8a, rutin showed slightly higher antibacterial activity than quercetin although its adsorption amount (Cf, 11.42 mg/g) was slightly lower than that of quercetin (Cf, 15.33

21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

mg/g). This is also an unexpected phenomenon, which is considered to originate from the high extent of the desorption of rutin from silk in the bacteria solution during the process of antibacterial activity test.

Figure 8. Correlation of the antibacterial activity of the treated silk with the initial application concentration (a) and adsorption quantity (b) of quercetin and rutin.

UV Protection Performance. It is common knowledge that overexposure to solar UV radiation may lead to increasing skin problems. Hence, developing UV protective clothes is a simple and effective measure to reduce or prevent the skin risks. Because the UVC (100–280 nm) is blocked by the earth's atmosphere, the UVA (315–400 nm) and UVB (280–315 nm) radiations exert considerable influence on the UV protection performance of textiles.33 Most of silk fabrics have poor UV protection ability because of their lightweight character. The untreated fabric showed high UV transmittance in the UV-A and UV-B region ranging from 290 to 450 nm (Figures 9a and 9b), and accordingly had a very low UPF of 4.91 (Figure 9c). Both of quercetin and rutin exhibited obvious absorption peaks

22


Page 22 of 35

Page 23 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


in the UV light region as shown in Figure 2, suggesting their potential application as UV protection finishing agents. As depicted in Figure 9a, the silk fabrics treated with low concentration (2% owf) of quercetin and rutin were effective in preventing the transmittance of UVA and UVB. Moreover, quercetin showed higher capability than rutin for reducing the transmittance of UVA and UVB through silk fabric at the same initial concentration (Figure 9b), giving rise to its higher UPF values (Figure 9c). Figure 9d shows the relationships between the UPF of the treated silk and the adsorption amount of quercetin and rutin. Clearly, the UPF of silk fabric did not increase obviously with increasing adsorption quantity of quercetin, implying that the UV protection ability of silk fabric is also restricted by the aggregation density of fibers in fabric. At almost the same adsorption quantity, quercetin showed slightly higher UPF than rutin. For example, the UPF of the quercetin treated silk fabric was 26.39 at Cf=8.46 mg/g quercetin, while that of the rutin treated silk fabric was 23.05 at Cf=8.81 mg/g. This is directly related to the fact that quercetin possesses higher UV absorption intensity than rutin, as shown in Figure 2.

23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 9. UV transmittance curves (a), UVA and UVB transmittance (b), UPF (c) and UV protection efficiency (d) of silk fabrics treated with quercetin and rutin at various concentrations.

Durability of Functionalities. In this section, the functionalities of the quercetin and rutin treated silk fabrics subjected to repeated washing were explored in order to clarify their durability. The fabrics treated with 2% and 8% owf quercetin and rutin were employed to assess the durability of antioxidant activity and UV protection ability, and the 8% owf quercetin or rutin treated silk was used to explore the durability of antibacterial performance. As seen in Figure 10a, the antioxidant activity of the treated silk decreased with increasing washing cycle. However, the decline of antioxidant activity was greater for the rutin treated silk than for the quercetin treated silk. For the 8% owf quercetin treated silk, its antibacterial activity values against E. coli and S. aureus decreased to 70.2%

24


Page 24 of 35

Page 25 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and 74.8%, respectively after 10 washing cycles, but they were always higher than those of the rutin treated silk (Figure 10b). The UPF of the quercetin treated silk showed little variations after 10 washing cycles, while for the silk treated with 2% and 8% owf rutin, its UPF declined to 9.44 and 13.86, respectively (Figure 10c). Figure 10 reveals that the rutin treated silk had an obvious reduction in functionalities after 10 washing cycles in comparison with the quercetin treated silk. These results are in close relationship with the differences in the affinity of quercetin and rutin to silk fiber, and the desorption performance (Figure S1, Supporting Information) of quercetin and rutin from silk fiber in water. On the other hand, considering practical applications, the development of the multifunctional materials with distinctive washing durability is also the target in order to cater to different demands. For instance, in the case that the multifunctional silk has to be subjected to repeated washing cycles during its life time, the quercetin treated silk is desirable. To manufacture the medical materials with sustained release of antioxidants during usage, rutin treated silk is the better choice. In the light of the tests on the functionality durability and flavonoid desorption of the treated silk, a low dosage (2% owf) of quercetin is sufficient for the manufacture of the washing resistant and functional silk materials, whilst a high concentration (8% owf) of rutin is suitable for the preparation of the medical materials with sustained release function.

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 10. Functionality changes of the quercetin and rutin treated silk after repeated washing: antioxidant activity (a), antibacterial activity (b) and UV protection performance (c).

26


Page 26 of 35

Page 27 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Changes in the surface morphology, thermal stability and mechanical performance of silk. No changes or small changes in the morphological structure, thermal stability and mechanical property of silk fiber which is subjected to functional modification are important for practical applications. Thus, the related changes were studied in the present study. The morphological structures of silk fabrics were observed by SEM and shown in Figure S2 (Supporting Information). Obviously, the treated silk fiber showed a clean and smooth surface as the untreated sample did, revealing that the morphological structure of silk fiber is not affected by the quercetin and rutin treatment. Additionally, the aggregates of quercetin and rutin were not found on the silk surface, indicating that quercetin and rutin diffuse into the fiber interior in the adsorption process. The thermal stability of the untreated and treated silk was investigated by TG analyses. As depicted in Figure S3 (Supporting Information), the treatment processes involving quercetin and rutin had a marginal effect on the thermal stability of silk. The evaluation of tensile strength was implemented by measuring the maximum stress of stress–strain plot at the beginning of the breaking of the fabric. The stress–strain plots which represent the average values are shown in Figure S4 (Supporting Information). The mean tensile strength and elongation of the untreated sample at break were 461.2 ± 5.3 N and 26.2% ± 1.5%, respectively. The quercetin and rutin treated samples had the average tensile strength of 428.0 ± 5.8 N and 428.1 ± 6.3 N, respectively, and their average elongation were 35.3% ± 2.5% and 36.9% ± 1.7%, respectively. The tensile strength deterioration of the quercetin and rutin treated fabrics

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

is caused by the hydrolysis of silk fiber at low pH and high temperature. For the wet processing of silk, a small decrease in tensile strength is permissible and may not have great impact on the application of silk fabric. After the treatment, silk fabric had a slightly increased elongation which is mainly attributed to the swelling of silk fiber, leading to the shrinkage of silk fabric.

CONCLUSIONS In the present work, two flavonoids (quercetin and rutin) with similar structures were applied to prepare multifunctional silk materials by an adsorption technique. The adsorption kinetics of quercetin and rutin onto silk obeyed the pseudo second-order kinetic model, and the equilibrium adsorption isotherms fitted well to the Langmuir and Freundlich adsorption models. Quercetin exhibited a higher adsorption capability towards silk than rutin because of its high affinity to silk, and conferred better antibacterial, antioxidant, and UV protection performance to silk than rutin at the same initial application concentration. However, at almost the same adsorption quantity, rutin imparted slightly higher antibacterial and antioxidant activity to silk due to its higher extent of desorption from silk in aqueous solution caused by its low affinity to silk. Additionally, the functionalities of the quercetin treated silk showed better washing resistance than those of the rutin treated silk. In conclusion, quercetin is favorable for the manufacture of the functional silk materials subjected to repeated washing, whilst rutin is suitable for the preparation of the medical materials with sustained release of antioxidants during usage.

28


Page 28 of 35

Page 29 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.xxxxxxx. Desorption rate of quercetin and rutin from the treated silk in water; SEM images, TG curves, and stress-strain curves of the untreated, quercetin treated, and rutin treated silk fabrics (PDF).

AUTHOR INFORMATION Corresponding Author *Ren-Cheng Tang. E-mail: [email protected]. Fax: +86 512 6724 6786. Tel.: +86 512 6716 4993

ORCID Ren-Cheng Tang: 0000-0001-7220-860X Yuyang Zhou: 0000-0003-3808-5778

Notes The authors declare no competing financial interest.

ACKNOWLEDGEMENTS This study was funded by Jiangsu Provincial Key Research and Development

29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 35

Program of China (BE2015066), the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions (No. 2014-37) and the Research Innovation Program for College Graduates of Jiangsu Province (KYLX16_0137).

REFERENCES (1) Shahid-ul-Islam; Shahid, M.; Mohammad, F. Perspectives for natural product based agents derived from industrial plants in textile applications-a review. J. Cleaner.

Prod. 2013, 57, 2–18. DOI 10.1016/j.jclepro.2013.06.004. (2) Shahid, M.; Shahid-ul-Islam; Mohammad, F. Recent advancements in natural dye applications:

a

review.

J.

Clean.

Prod.

2013,

53,

310–331.

DOI

10.1016/j.jclepro.2013.03.031. (3) Shahid-ul-Islam; Mohammad, F. Natural colorants in the presence of anchors so-called mordants as promising coloring and antimicrobial agents for textile materials.

ACS

Sustainable

Chem.

Eng.

2015,

3,

2361–2375.

DOI 10.1021/acssuschemeng.5b00537. (4) Zhou, Y.; Zhang, J.; Tang, R.-C.; Zhang, J. Simultaneous dyeing and functionalization of silk with three natural yellow dyes. Ind. Crop. Prod. 2015, 64: 224–232. DOI 10.1016/j.indcrop.2014.09.041. (5) Li, G.; Liu, H.; Li, T.; Wang, J. Surface modification and functionalization of silk fibroin fibers/fabric toward high performance applications. Mat. Sci. Eng. C 2012,

32, 627–636. DOI 10.1016/j.msec.2011.12.013. (6) Zhou, Y.; Yang, Z.-Y.; Tang, R.-C. Bioactive and UV protective silk materials

30


Page 31 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


containing baicalin–The multifunctional plant extract from Scutellaria baicalensis Georgi. Mater. Sci. Eng. C 2016, 67, 336–344. DOI 10.1016/j.msec.2016.05.063. (7) Abbasi, A.R.; Akhbari, K.; Morsali, Ali. Dense coating of surface mounted CuBTC Metal–Organic Framework nanostructures on silk fibers, prepared by layer-by-layer method under ultrasound irradiation with antibacterial activity. Ultrason. Sonochem.

2012, 19, 846–852. DOI 10.1016/j.ultsonch.2011.11.016. (8)

Abbasi,

A.R.;

Bohloulzadeh,

M.;

Morsali,

A.

Preparation

of

AgCl

nanoparticles@ancient textile with antibacterial activity under ultrasound irradiation.

J. Inorg. Organomet. Polym. 2011, 21, 504–510. DOI 10.1007/s10904-011-9484-8. (9) Pietta, P.-G. Flavonoids as antioxidants. J. Nat. Prod. 2000, 63, 1035–1042. DOI 10.1021/np9904509. (10) Altıok, E., Bayçın, D., Bayraktar, O., Ülkü, S. Isolation of polyphenols from the extracts of olive leaves (Olea europaea L.) by adsorption on silk fibroin. Sep. Purif.

Technol. 2008, 62, 342–348. DOI 10.1016/j.seppur.2008.01.022. (11) Grifoni, D.; Bacci, L.; Lonardo, S. D.; Pinelli, P.; Scardigli, A.; Camilli, F.; Sabatini, F.; Zipoli, G.; Romani, A. UV protective properties of cotton and flax fabrics dyed with multifunctional plant extracts. Dyes Pigm. 2014, 105, 89–96. DOI 10.1016/j.dyepig.2014.01.027. (12) Nijveldt, R. J.; Nood, E.; Hoorn, D. E. C.; Boelens, P. G.; Norren, K.; Leeuwen, P. A. M. Flavonoids: a review of probable mechanisms of action and potential applications. Am. J. Clin. Nutr. 2001, 74, 418–425. (13) Cruz-Zúñiga, J. M.; Soto-Valdez, H.; Peralta, E.; Mendoza-Wilson, A. M.;

31



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 35

Robles-Burgueño, M. R.; Auras, R.; Gámez-Meza, N. Development of an antioxidant biomaterial by promoting the deglycosylation of rutin to isoquercetin and

quercetin.

Food

Chem.

2016,

204,

420–426.

DOI

10.1016/j.foodchem.2016.02.130. (14) Plaza, M.; Pozzo, T.; Liu, J.; Ara, K. Z. G.; Turner, C.; Karlsson, E. N. Substituent effects on in vitro antioxidizing properties, stability, and solubility in flavonoids. J.

Agric. Food Chem. 2014, 62, 3321−3333. DOI 10.1021/jf405570u. (15) Aherne, S. A.; O’Brien, N. M. Dietary flavonols: chemistry, food content, and metabolism, Nutrition 2002, 18, 75–81. DOI 10.1016/S0899-9007(01)00695-5. (16) Kato, K.; Ninomiya, M.; Tanaka, K.; Koketsu, M. Effects of functional groups and sugar composition of quercetin derivatives on their radical scavenging properties. J.

Nat. Prod. 2016, 79, 1808−1814. DOI 10.1021/acs.jnatprod.6b00274. (17) Samsonowicz, M.; Regulska, E. Spectroscopic study of molecular structure, antioxidant activity and biological effects of metal hydroxyflavonol complexes.

Spectrochim. Acta Part A 2017, 173, 757–771. DOI 10.1016/j.saa.2016.10.031. (18) Re, R.; Pellegrini, N.; Proteggente, A.; Pannala, A.; Yang, M.; Rice-Evans, C. Antioxidant activity applying an improved ABTS radical cation decolorization assay.

Free

Radic.

Biol.

Med.

1999,

26,

1231−1237.

DOI

10.1016/S0891-5849(98)00315-3. (19) Zhou, Y.; Tang, R.-C. Modification of curcumin with a reactive UV absorber and its dyeing and functional properties for silk. Dyes Pigm. 2016, 134, 203–211. DOI 10.1016/j.dyepig.2016.07.016.

32


Page 33 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(20) Luo, Z.; Murray, B. S.; Ross, A. -L.; Povey, M. J. W.; Morgan, M. R. A.; Day, A. J. Effects of pH on the ability of flavonoids to act as pickering emulsion stabilizers.

Colloid Surface B 2012, 92, 84–90. DOI 10.1016/j.colsurfb.2011.11.027. (21) Nasirizadeh, N.; Dehghanizadeh, H.; Yazdanshenas, M. E.; Moghadam, M. R.; Karimi, A. Optimization of wool dyeing with rutin as natural dye by central composite

design

method.

Ind. Crop.

Prod.

2012, 40,

361–366.

DOI

10.1016/j.indcrop.2012.03.035. (22) Weiz, G.; Breccia, J. D.; Mazzaferro, L. S. Screening and quantification of the enzymatic deglycosylation of the plant flavonoid rutin by UV-visible spectrometry.

Food Chem. 2017, 229, 44–49. DOI 10.1016/j.foodchem.2017.02.029. (23) Jovanovic, S. V.; Steenken, S.; Tosic, M.; Marjanovic, B.; Simic, M. G. Flavonoids as

antioxidants.

J.

Am.

Chem.

Soc.

116,

1994,

4846–4851.

DOI 10.1021/ja00090a032. (24) Torreggiani, A.; Tamba, M.; Trinchero, A.; Bonor, S. Copper(II)–Quercetin complexes in aqueous solutions: spectroscopic and kinetic properties. J. Mol. Struct.

2005, 744–747, 759–766. DOI 10.1016/j.molstruc.2004.11.081. (25) Herrero-Martínez, J. M.; Sanmartin, M.; Rosés, M.; Bosch, E.; Ràfols, C. Determination of dissociation constants of flavonoids by capillary electrophoresis.

Electrophoresis 2005, 26, 1886–1895. DOI 10.1002/elps.200410258. (26) Singh, O.; Kaur, R.; Mahajan, R. K. Flavonoid-surfactant interactions: a detailed physicochemical

study.

Spectrochim.

Acta

A

2017,

10.1016/j.saa.2016.07.007.

33


170,

77–88.

DOI


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 35

(27) Jurasekova, Z.; Domingo, C.; Garcia-Ramos, J. V.; Sanchez-Cortes, S. Effect of pH on the chemical modification of quercetin and structurally related flavonoids characterized by optical (UV-visible and Raman) spectroscopy. Phys. Chem. Chem.

Phys. 2014, 16, 12802–12811. DOI 10.1039/C4CP00864B. (28) Ho, Y. S.; McKay, G. Pseudo-second order model for sorption processes. Process

Biochem. 1999, 34, 451–465. DOI 10.1016/S0032-9592(98)00112-5. (29) Chairat, M.; Rattanaphani, S.; Bremner, J. B.; Rattanaphani, V. An adsorption and kinetic study of lac dyeing on silk. Dyes Pigm. 2005, 64, 231–241. DOI 10.1016/j.dyepig.2004.06.009. (30) Ramešová, Š.; Sokolová, R.; Degano, I.; Bulíčková, J.; Žabka, J.; Gál, M. On the stability of the bioactive flavonoids quercetin and luteolin under oxygen-free conditions.

Anal.

Bioanal.

Chem.

2012,

402,

975–982.

DOI

10.1007/s00216-011-5504-3. (31) Lemańska, K.; Szymusiak, H.; Tyrakowska, B.; Zieliński, R.; Soffers, A. E.; Rietjens, I. M. The influence of pH on antioxidant properties and the mechanism of antioxidant action of hydroxyflavones. Free Radical Bio. Med. 2001, 31, 869–881. DOI 10.1016/S0891-5849(01)00638-4. (32) Kumar, S.; Pandey, A. K. Chemistry and biological activities of flavonoids: an overview. The Scientific World J. 2013, 2013, 162750. DOI 10.1155/2013/162750. (33) Sun, S. -S.; Tang, R. -C. Adsorption and UV protection properties of the extract from honeysuckle onto wool. Ind. Eng. Chem. Res. 2011, 50, 4217–4224. DOI 10.1021/ie101505q.

34


Page 35 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only (TOC Graphic)

Synopsis Quercetin and rutin are employed to impart antibacterial, antioxidant and UV protection properties to silk fiber by an adsorption technique.

35


Natural Flavonoid-Functionalized Silk Fiber Presenting Antibacterial

Recommend Documents