Developed functionalization of wool fabric with extracts of Lycium ruthenicum Murray and potential application in healthy care textiles

Dyes and Pigments 163 (2019) 308–317

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Developed functionalization of wool fabric with extracts of Lycium ruthenicum Murray and potential application in healthy care textiles

T

Yongchun Donga,b,∗, Jiayu Gua, Peng Wanga, Hongjie Wena a b

Division of Textile Chemistry & Environmental Care, School of Textile Science and Engineering, Tianjin Polytechnic University, Tianjin, 300387, China Key Laboratory of Advanced Textile Composite of Ministry of Education, Tianjin Polytechnic University, Tianjin, 300387, China

A R T I C LE I N FO

A B S T R A C T

Keywords: Lycium ruthenicum Murray Anthocyanidins Functionalities Wool fabric Dyeing process

To develop healthy care textiles, Lycium ruthenicum Murray (abbreviated as LRM in the following) extracts were prepared in both different media and characterized, respectively for the functionalizing of wool fabric by an exhaustion dyeing process. The antimicrobial and antioxidant activities of both LRM dyed wool fabric were then investigated and compared. Enhanced effect of Fe ions as the post mordants on functionalities and durability of the dyed fabrics was also examined. The results indicated that LRM ethanol extract was found to contain more anthocyanins than LRM water extract. LRM dyed wool fabric showed antimicrobial and antioxidant activities. Increasing color strength could enhance their functionalities. Treatment of Fe ions, especially Fe3+ led to the durable functionalities. Compared with the dyed wool fabric with Lycium barbarum L. extract, LRM dyed wool fabric exhibited strong functionalities.

1. Introduction In recent years, healthy care textiles have been become the fastest growing sectors in the technical textile market throughout the world due mainly to their multi-functionalities, especially health-enhancing effect [1,2]. Furthermore, rapid growth in the population and increasing standard of living, especially in developing areas have led to a huge need for healthcare textiles. It is known that an antibacterial and anti-oxidative acting formulation should serve as a functional textile finishing primary for healthcare or medical fabrics [3], which can protect people from getting infected by harmful microorganisms or prevent the oxidative stress caused by harmful species such as active oxygen radicals [4,5]. The previous literature [3,6–8] revealed that healthy care textiles were often processed with a number of chemicals, especially aromatic amines, formaldehyde-containing compounds and phenols derivatives, etc to enhance their functionalities. It should be noticed that when selecting the active substances for textile finishing, it must be ensured that these substances are not only permanently effective, but also compatible with human body and natural environment [2]. However, the main disadvantage of these chemical substances is their high toxicity and poor environmental compatibility [3], which should be severely limited from the view point of environmental care and health protection legislation. Because of this, some bioactive extracts from plants as renewable and sustainable bioresource products

have been gradually applied in the textile process, which has great vitality and promising prospects in the development of healthcare textiles. The majority of bioactive extracts from natural products such as isoflavones from the soybean [9], phenols from olive oil [10] or polyphenols from the grape or tea [11] have been applied for different textiles [5]. Moreover, flavonoids are known as powerful agents to functionalize textiles, and account for the largest proportion in the family of natural bioactive extracts [3,12]. Lycium ruthenicum Murray (LRM for short) is a medicinal and edible plant distributed in Europe, central Asia and northwestern China, and its fruit has been used as a remedy for treating of many diseases to humans such as abnormal menstruation and heart disease [13,14]. The extracts from LRM fruits were found to contain abundant anthocyanins [14], which were shown as a subgroup of flavonoids to provide many potential health-enhanced effects on human body including antiatherosclerotic, immune-enhancing, anti-fatigue, and antioxidant and anticancer [15–17]. Besides, recent research confirmed that most of the anthocyanins from LRM fruits were acylated anthocyanins [18,19], which showed higher antioxidant activity than the corresponding anthocyanidins and their glycoside forms [20,21]. In recent years, many studies [14–19] have concentrated on the isolation and identification of anthocyanins from the extracts of LRM fruits. However, little research has been devoted to the application of LRM extracts for preparing functional fabrics, especially healthy and environmental care textiles.

∗ Corresponding author. Division of Textile Chemistry & Environmental Care, School of Textile Science and Engineering, Tianjin Polytechnic University, 399 Bingshui West Road, Xiqing District, Tianjin, 300387, China. E-mail addresses: [email protected], [email protected] (Y. Dong).

https://doi.org/10.1016/j.dyepig.2018.12.011 Received 15 August 2018; Received in revised form 6 December 2018; Accepted 6 December 2018 Available online 08 December 2018 0143-7208/ © 2018 Published by Elsevier Ltd.

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Hence, in this present work, LRM fruits were first extracted using ethanol and deionized water as the medium, respectively. The obtained LRM extracts were then characterized and used for the functionalizing of wool fabric through a simple dyeing method because LRM extracts have been used as an alternative to synthesized colorants in food industry [13]. Additionally, the application of LRM extracts makes it possible to combine dyeing and finishing processes of wool fabric, showing a great advantage of low consumption of water and energy. Accordingly, the functionalizing process of wool fabric with the two LRM extracts was conducted and optimized with respect to its color strength. The antimicrobial and antioxidant activities of the dyed wool fabrics with the two LRM extracts were investigated and compared. And the dyed wool fabric was then treated with two iron salts as the post mordants, respectively and their enhanced effect on functionalities and stabilities of the resulting fabric was studied. Finally, LRM dyed wool fabric was found to be strong functionalities by comparing with the dyed wool fabric with a traditional Lycium barbarum. L (LBL for short) fruit extract.

anthocyanins were main components in LRM extracted samples, and more than 10 anthocyanins were detected. Accordingly, total anthocyanin content in LRM extract was measured by the pH differential method described by Lee et al. [22] in this present study. In a brief process, 0.5 mL of LRM extract was added into 9.5 mL of KCl buffer solution (pH = 1.0) and CH3COONa buffer solution (pH = 4.5), respectively. The resulting mixtures were then equilibrated at 25 °C for 15 min, and their absorbance values were tested by a UV-2401 Shimadzu spectrophotometer at 528 nm (λmax of LRM extract) and 700 nm in buffer solutions at pH 1.0 and 4.5. Total anthocyanin content (TAC, mg/100 g) was calculated through Eq. (1).

TAC =

[(A528 − A700 ) pH 1 − (A528 − A700 ) pH 4.5] × MW × DF × V ε ×M

(1)

where A528 and A700 are absorbances at 528 nm and 700 nm, respectively, ε is molar absorptivity (cyanidin 3-glucoside: 25965 cm−1M−1), V is total volume of LRM extract, and MW is molecular weight of cyanidin 3-glucoside (449). DF refers to diluted factor.

2. Experimental

2.3. Functionalizing method of wool fabric with both LRM extracts

2.1. Materials and reagents

Functionalization of wool fabric with the LRM extract was achieved by a regular exhaustion dyeing process using a laboratory dyeing machine with 12 glass tubes (Xiamen Rapid Precision Machinery Co., China). The dye bath was comprised of LRM extract and deionized water, and pH level of the dye bath was adjusted with diluted HCl or NaOH aqueous solution. The wool fabric specimens were immersed in dye bath at a liquor ratio of 1:30. Dyeing of wool fabric was carried out with the dye baths containing different amounts of LRM extract at the requisite temperature for a given time. After the dyeing, the resulting wool fabric was taken out from the baths and then washed using warm water, followed by cold rinses and finally dried at 60 °C for 15 min. In order to enhance the functionalities of the LRM dyed wool fabric, a post mordant treatment was used with different iron salts (FeSO4 and Fe2(SO4)3) at a liquor ratio of 1: 30. Iron salt concentration varied from 3 to 20% owf. LRM dyed wool fabric was placed into iron salt aqueous solutions at 60 °C for 30 min. Subsequently, the resulting fabrics were rinsed and then air dried. To evaluate the adsorption content of LRM extract, especially anthocyanins on the dyed wool fabric, the surface color strength (K/S) of which was determined using a SF-600 spectrophotometer (Datacolor International, USA) under a D65 illuminant with a 10° standard observer. K/S value of the dyed fabric can be built through the KubelkaMunk equation [23]:

The dry fruits of LRM and LBL were purchased by Ningxia QYCL Biological Company (Ningxia, China). They were first cleaned with warm deionized water repeatedly, and then dried at 60 °C under vacuum and subsequently crushed into powders before use. Commercially available wool woven fabric (247.93 gm−2) was used in this work, and further treated by washing in acetone for 3 h in an ultrasonic bath to remove the impurities. Fabric samples were taken out and then dried at 50 °C. Ethanol, pyrogallic acid, H2O2 (30%w⁄w), FeSO47H2O and Fe2(SO4)3 were of analytical grade and used as received. Deionized water was used in whole work. 2.2. Preparation and characterization of LRM extracts 2.2.1. Extraction process with 80% ethanol/water The desired weight of LRM powders were put into a round bottom flask equipped with a reflux condenser, and a mixture of ethanol: water (80:20, v/v) was then added with a solid-to-liquid ratio of 1:30. Extraction process was performed at pH 2 in thermostatic water bath by continuous stirring at 65 °C for 3 h. After cooling to ambient temperature, the extracted liquid was centrifuged at 4000 rpm for 20 min to collect the supernatant, and then rapidly filtered through a Buchner funnel to remove all the residues. The resulting filtrate was transferred into 100 mL volumetric flask and denoted as LRM-e.

K/S =

(1 − R)2 2R

(2)

where R is the reflectance of the dyed fabric, K is the absorption coefficient, and S is the scattering coefficient. To confirm the status of Fe ions deposited on the LRM dyed wool fabrics, a Hitachi S-4800 fieldemission scanning electron microscopy with EDX spectrometer was used to examine their surface structure and morphology before and after Fe ions treating.

2.2.2. Extraction process with water The LRM water extract (denoted as LRM-w) was prepared by mixing LRM powders with deionized water with a solid-to-liquid ratio of 1:30 at pH 2 and 85 °C in a constant-temperature water bath under continuous agitation for 3 h. Afterward, the same centrifuging and filtering processes described above were used to remove all the residues to obtain LRM-w.

2.4. Antibacterial activity evaluation 2.2.3. Characterization of both LRM extracts Both LRM extracts were examined using a UV-2401 Shimadzu spectrophotometer and a Nicolet Magna-560 Fourier Transform-infrared (FTIR) spectrometer (Nicolet Inc., USA) with a 4 cm−1 resolution, respectively for their composition analysis. Thermo-gravimetric analysis (TGA) measurement for the powder from LRM extracts was conducted using Q600 SDT Simultaneous DSC-TGA thermal analyzer under nitrogen atmosphere at heating rate of 10 °Cmin-1 with a sample weight of 10 mg. The solid contents in LRM extracts were calculated by determining the unchanged weight loss after heat treatment at 105 °C. Also, some previous investigations [13,18] confirmed that

Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as model bacteria to assess the antibacterial activity of LRM dyed fabrics by the method described in ASTM E2149-2013 [15] with some modification in this present study. The antibacterial activity was expressed by the percentage of bacterial reduction after contact with the LRM dyed wool fabric compared to the number of bacterial colonies surviving after contact with the original wool fabric as control sample. After the antibacterial test, bacteria colonies were counted using Scan 500 Colony Counter (Interscience, France), and the percentage of bacterial reduction was calculated by Equation (3). 309

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Fig. 1. FTIR (a), UV–Vis (b) spectra as well as solid content and total anthocyanin content (inset) and TGA and DTA curves (c) of both LRM extracts.

Fig. 2. K/Smax values of LRM dyed wool fabrics at varied conditions.

R (%) =

B−A × 100% B

dyed and original wool fabric, respectively after 12 h contact time. (3)

where R(%) is the percentage of bacterial reduction. A and B are the number of the visual bacterial colonies for the plates containing the 310

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control. The superoxide radical inhibition ability was expressed as:

ΔA325nm, control − Inhibition(%) = ⎛ t ⎝ ⎜

ΔA325nm, sample ΔA325nm, control × 100%⎞ / t t ⎠ (5) ⎟

Where ΔA325nm,control is the increase in the A325nm value of the mixture with the untreated wool fabric. ΔA325nm,sample is the increase in the A325nm value of the mixture with the dyed wool fabric. t is the time required for the determination (5 min in this case).

Fig. 3. Decomposition reaction of anthocyanin molecule at pH > 6.

2.5. Antioxidant activity determination 2.6. Color characteristics measurement

2.5.1. Hydroxyl radical scavenging assay The hydroxyl radical scavenging activity of the LRM dyed wool fabric was determined using a modified test method as reported by Smirnoff et al. [24]. In a typical procedure, 50 mg of the dyed wool fabric was immersed in mixed solution containing 2.0 mL of FeSO4 aqueous solution (6.0 mmolL−1) and 2.0 mL of salicylic acid solution (6.0 mmolL−1), followed by the addition of 2.0 mL of H2O2 (6.0 mmolL−1). The resulting mixture was incubated at 37 °C for 60 min. The absorbance of the mixture at 510 nm was determined by a UV-2401 spectrophotometer (Shimadzu Co. Japan). The inhibition rate of hydroxyl radicals was calculated according to Equation (4).

A Inhibition(%) = ⎛1 − s ⎞ × 100% A c⎠ ⎝ ⎜

Before testing, LRM dyed wool fabrics were conditioned at 25 °C and 65% RH for at least 24 h. Their color characteristic values including L*, a*, b*, c* and h° values were analyzed using a SF-600 spectrophotometer (Datacolor International, USA) under a D65 illuminant with a 10° standard observer. L*, a*, b*, c* and h° are lightness, rednessgreenness, yellowness-blueness, saturation and hue, respectively. 2.7. Color fastness evaluation Color fastnesses to washing, rubbing and light of LRM dyed wool fabrics were tested and evaluated before and after Fe ions treatment according to Chinese Textiles Test Specification for Color Fastness (GB/ T3921-2008, GB/T3920-2008 and GB/T8426-2008), correspondingly, which are based on ISO international standards.

⎟

(4)

where Ac and As refer to the absorbance of the hydroxyl radical at 510 nm in the absence and presence of the dyed wool fabric, respectively.

3. Results and discussion 3.1. Characterization of LRM extracts

2.5.2. Superoxide radical scavenging test The superoxide radical scavenging activity was measured in accordance with a method developed by Li et al. [25]. In brief, the dyed wool fabric were added into mixture solution containing Tris-HCl buffer (2 mL, 50 mmolL−1, pH 8.2) and pyrogallol (0.5 mL, 6.0 mmolL−1 in 10.0 mmolL−1 HCl), and then the resulting mixture was vigorously shaken at 37 °C before being analyzed at 325 nm every 30 s for 5 min. The slope of the correlation of absorbance with time was calculated. The mixture solution with the untreated wool fabric was used as the

Both LRM extracts (LRM-e and LRM-w) were prepared with 80% ethanol/water and only water, respectively and then characterized by UV–Vis and FTIR spectra, respectively. Meanwhile, their solid content and total anthocyanin content were also measured, and the results were presented in Fig. 1. Several typical absorption peaks of LRM-e were observed from Fig. 1 (A) to be at 3414 cm−1, 2931 cm−1, 1732 cm−1, 1618 cm−1, and Fig. 4. Photographs of survival S. aureus (1) and E. coli (2) colonies on the agar Petri dish after 12 h of static contact with original wool fabric (a), LRM-e-W (b) or LRM-w-W (c). R% and K/Smax values of both LRM dyed wool fabrics (d). Relationship between K/Smax of LRM dyed wool fabrics and Inhibition% for both free radicals (e and f).

311

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Fig. 5. K/S curves of both LRM dyed wool fabrics (a and b) and their antibacterial (c) and antioxidant (d) activities before and after Fe ions treatment.

and B) bonded to a heterocyclic ring (C) with oxygen [30]. Accordingly, it was believed that LRM-e was composed mainly of anthocyanin compounds. LRM-w showed a similar FTIR spectrum to LRM-e. However, the peak at 1720 cm−1 became much less intensive and the OH group peak shifted to lower position, which may be attributed to the partial hydrolysis of anthocyanins in water during the water extraction process [30]. As shown in Fig. 1 (B), both strong characteristic adsorption peaks was clearly observed at about 285–315 nm and 530 nm (maximum absorbance wavelength in the visible region, λvis-max), respectively for both LRM extracts, which was similar to the UV–Visible spectra of anthocyanins in wild LRM fruit [31] and other fruits [32]. Moreover, both peaks for LRM-e was more intensive than that for LRMw, indicating that there were more anthocyanins in LRM-e than in LRMw, which was agreed with the total anthocyanin content in both LRM extracts in Fig. 1 (B) inset. It is known that the ratio of A310/Avis-max was used to estimate the acylation pattern of anthocyanins [31]. A310/Avismax were calculated to be 0.15 and 0.22 for LRM-e and LRM-w, correspondingly, demonstrating that the anthocyanins in both LRM extracts were the acylated anthocyanins, which was agreed well with the results reported by Zheng and Hu et al. [18,19]. In order to obtain a deep insight into both LRM extracts, their TG and DTG curves were shown in Fig. 1 (C). It was seen that their thermal decomposition in nitrogen proceeds by only one step, and during which a maximum weight loss was seen at about 150 °C, which was similar to thermal performance of the anthocyanins from black soybean [33]. Accordingly, the subsequent functionalization of wool fabric with both LRM extracts could be successfully completed by a conventional exhaustion dyeing process at the temperature below 100 °C.

Table 1 Effect of Fe ions on color characteristics of LRM-e dyed wool fabric. Samples

LRM-e-W LRM-e-W-Fe2+

LRM-e-W-Fe3+

Fe ions Conc. (owf %)

0 5 10 15 20 5 10 15 20

Color characteristics L*

a*

b*

c*

h*

44.03 51.9 52.09 49.56 47.76 45.47 44.75 44.14 44.10

29.85 6.85 6.45 6.05 5.99 3.46 3.21 3.16 3.05

5.54 15.98 15.89 15.47 14.15 14.77 14.67 14.4 13.82

27.45 17.02 17 16.76 15.37 15.11 14.98 14.74 14.09

11.64 69.88 69.15 67.37 67.07 78.25 77.74 77.63 76.65

Table 2 Effect of Fe ions on color characteristics of LRM-w dyed wool fabric. Samples

LRM-w-W LRM-w-W-Fe2+

LRM-w-W-Fe3+

Fe ions Conc. (owf %)

0 5 10 15 20 5 10 15 20

Color characteristic L*

a*

b*

c*

h*

44.8 56.84 56.62 55.69 55.01 48.36 46.95 46.64 45.06

26.88 3.62 3.03 2.79 2.67 1.52 1.47 0.51 0.3

3.07 16.05 15.2 14.45 13.77 13.68 13.25 12.5 11.63

30.01 16.46 15.5 14.72 14.02 13.76 13.33 12.51 11.63

5.87 79.08 79.03 78.73 77.28 88.53 87.69 83.69 83.65

1033 cm−1 owing to the stretching vibration of OH, CH, C]O and C]C [26,27]. Additionally, there was a characteristic adsorption between 500 and 950 cm−1, which was attributed to the vibration modes of benzene rings [27]. These characteristic peaks were also found from the IR spectra of anthocyanins in several plant extract samples [26,28,29]. As shown in Fig. 1 (D), anthocyanidins contain two aromatic rings (A

3.2. Optimization of wool fabric dyeing process with LRM extracts In order to obtain high adsorption amount of LRM extracts onto wool fabric, dyeing process was optimized by investigating and comparing the effect of several important variables on K/Smax value (K/S value at 530 nm of maximum absorbance wavelength in the visible region) of the LRM dyed wool fabric, and the results were given in 312

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Fig. 6. SEM images and EDX spectra of LRM-e-W (a) and LRM-w-W (b) before (1) and after treating of Fe2+ (2) or Fe3+ (3) ions.

aglycosidic forms of anthocyanins (anthocyanidins) [32] with similar molecular weight (900–1100) [31] to direct dyes. Accordingly, the anthocyanins may depend mainly on secondary forces such as hydrogen bonds and van der Waals forces to bond with wool fiber, although they are positively charged in acidic medium [30], which may reject the protonated terminal amino groups of wool fiber due to the electrostatic repulsion. Moreover, K/Smax value with LRM-e was higher than that with LRM-w at the same time, suggesting that more anthocyanins were deposited on wool fabric by using LRM-e, possibly because of relatively high total anthocyanin content in LRM-e. Additionally, the residual ethanol in LRM-e may have a favorable effect on anthocyanins adsorption on wool fiber through decreasing the surface tension between them [34]. A series of wool fabrics was dyed with a treating solution (100 mL) containing different amounts of LRM extracts at pH = 2 and 90 °C, and K/Smax values of the dyed fabrics were tested and presented in Fig. 2 (B). It was clear in that K/Smax values gradually rose with increasing dosage of both LRM extracts, which was mainly owing to the enhanced contact of anthocyanin molecules on fiber surface, therefore causing a strong anthocyanin adsorption. As shown in Fig. 2 (C), elevation of dyeing temperature increased K/Smax values, demonstrating that high temperature enhanced the anthocyanin adsorption on wool fiber. A reason is that the cuticle on the surface of wool fiber acts as a barrier to the diffusion of LRM extracts. High temperature could enhance the

Scheme 1. Proposed simultaneous coordinating modes of Fe ions with LRM extract and wool fiber.

Fig. 2. Fig. 2 (A) shows K/Smax values of the dyed wool fabrics with both LRM extracts with a liquor ratio of 1:30 at pH = 3 and 90 °C for different periods, respectively. It was found that K/Smax values gradually increased with the extension of dyeing time, and became flat from 80 min to 100 min, proposing that the anthocyanins in LRM extracts were constantly adsorbed onto wool fabric at the beginning stage of dyeing process, and the adsorption equilibrium was then almost reached over 80 min. This indicated that the almost unchanged amount of LRM extracts could be deposited on wool fabric after 80 min of dyeing time. This is because as described earlier, the anthocyanins in LRM extracts are the acylated anthocyanins, which are confirmed as the 313

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Table 3 Antibacterial and antioxidant activities of dyed wool fabrics after different washing cycles. Parameters

R (%)

Inhibition (%)

E.coli Washing cycles LRM-e-W LRM-e-W-Fe2+ LRM-e-W-Fe3+ LRM-w-W LRM-w-W-Fe2+ LRM-w-W-Fe3+

0 72.0 88.8 97.5 62.9 70.7 76.1

5 42.1 73.6 82.8 48.3 54.3 63.0

S.aureus 10 31.9 56.8 79.7 47.1 53.5 58.2

0 74.5 94.5 98.1 65.4 76.3 77.5

5 54.3 75.6 85.5 53.7 57.1 63.9

Hydroxyl radical 10 46.8 74.6 81.3 51.7 55.1 63.2

LRM-e-W LRM-e-W-Fe2+ LRM-e-W-Fe3+ LRM-w-W LRM-w-W-Fe2+ LRM-w-W-Fe3+

Washing fastness

Rubbing fastness

Fading

SC

SW

Dry

Wet

3–4 4–5 4–5 3–4 4–5 4–5

5 4–5 5 4–5 4–5 5

5 5 5 5 5 5

5 5 5 5 5 5

4–5 4–5 5 4–5 4–5 5

5 54.3 65.2 69.0 28.5 57.1 81.0

10 53.3 64.2 67.9 25.6 50.0 79.2

0 88.4 88.7 89.9 65.4 90.9 96.3

5 69.3 73.4 76.1 37.4 58.6 83.8

10 68.0 70.7 74.8 26.8 52.1 80.6

As seen in Fig. 4(a–d), the number of bacteria colonies from both dyed wool fabrics were less than that from the original wool fabric. R% values for LRM-e-W against two bacteria were over 70%, which were slightly higher than those for LRM-w-W at the same conditions. These results indicated that LRM-e-W and LRM-w-W samples exhibited relatively higher antibacterial activity. Anthocyanins were regarded as the principal component responsible for the antibacterial effect of the dyed wool fabrics with LRM extracts, since the antibacterial effect of anthocyanins in some plants extracted samples was confirmed in several previous studies [35–37]. Moreover, the antibacterial mechanism of anthocyanins was reported to be a combined effect of the destabilisation of cytoplasmic membrane, permeabilization of plasma membrane, inhibition of extracellular microbial enzymes, direct actions on microbial metabolism and deprivation of the substrates required for microbial growth [35,36]. Thus, better antibacterial activity of LRM-e-W may mainly be attributed to high total anthocyanin content in LRM-e.

Table 4 Color fastnesses of LRM dyed wool fabric before and after Fe ions treatment. Samples

0 81.2 83.9 91.3 55.5 85.1 96.2

Superoxide radical

Light fastness

1 1–2 2–3 1 1–2 2–3

Staining on cotton fabric (SC), Staining on wool fabric (SW).

sufficient swelling of cuticle, thus increasing the penetration and wetting of LRM extract into wool fiber. Fig. 2 (D) displays the variation of K/Smax values with the pH level of dyeing bath. Increasing pH level led to an almost significant reduction in K/Smax values of both samples. It is known that anthocyanins exhibits different colors which depend on the pH of the solution [18,30]. Flavylium cation (red color) and blue quinoidal compounds are the predominant species at pH < 4. At pH values between 5 and 6, there are only two colorless carbinol pseudobase and chalcone in the solution. Moreover, the anthocyanins prefer to decompose at pH > 6 (Fig. 3) [34]. Therefore, it was conclude that pH level should be set between 2 and 3 to obtain the dyed wool fabric with high adsorption of anthocyanins when dyeing with LRM extracts.

3.4. Antioxidant activity study A series of wool fabrics was dyed with a treating solution (100 mL) containing varied volumes of LRM extracts at pH = 2 and 90 °C, and K/ Smax values and the hydroxyl and superoxide radicals scavenging activities of the LRM dyed fabrics were determined, respectively and both free radical inhibition% values were calculated and presented in Fig. 4(e and f). It was clear that inhibition% values for both free radicals in the presence of the original wool fabric were less than 15%, proposing that the original wool fabric had poor antioxidant activity. Whereas the LRM dyed wool fabric presented significantly enhanced antioxidant performance, and inhibition% values gradually increased with an increase in its K/Smax value. This was mainly due to increasing content of anthocyanins adsorbed on the LRM dyed wool fabrics with high K/Smax values. According to the previous studies [18,38], the anthocyanins in LRM extracts acted as strong antioxidant by contributing hydrogen atoms to highly reactive free radicals and inhibiting the free radical chain reaction. Moreover, the more hydroxyl group anthocyanins had the higher antioxidant activity it would be guaranteed to have. The antioxidant activity of anthocyanins mainly was dependent upon the aglycone. The acylated anthocyanins might have

3.3. Antibacterial evaluation Both wool fabrics with similar K/Smax values were firstly prepared through controlling the amount of both LRM extracts and dyeing conditions. After dyeing with both LRM extracts, the resulting dyed samples were then thoroughly rinsed with deionized water, and they were denoted as LRM-e-W and LRM-w-W for wool fabrics dyed with LRM-e and LRM-w, correspondingly. Antibacterial activities of both samples against E. coli and S. aureus as the model bacteria were examined in this work. As a comparison, a control experiment was performed, in which the original wool fabric was used, and the results were shown in Fig. 4(a–d).

Fig. 7. Multi-functionalities of dyed wool fabrics with LBL or LRM water extract. 314

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polarity of the metal ion, because of the partial sharing of its positive charge with donor groups, which in turn enhances the interaction between metal ion and the lipid as a main component of bacteria cell wall and membranes. This may break the permeability barrier of the cell, thus leading to interference with normal cell processes [42,43]. Also, Fe complexes are known for its DNA destroying performance due to the combination of the complexes with base pair of DNA helix [44,45]. Thus, a synergistic effect of anthocyanin ligand and the Fe ions acting together could occur, thus favoring the antibacterial property of the dyed wool fabrics after Fe ions treatment in this work. On the other hand, Fig. 5(d) demonstrated that Fe ions treating caused a little or slight enhancement in Inhibition% values for both free radicals, suggesting that the antioxidant activities of the dyed wool fabrics were hardly affected by Fe ions treating.

positive influence on their antioxidant activity. Besides, comparing both fabrics with different LRM extracts, LRM-e-W possessed higher antioxidant activity for both free radicals than LRM-w-W at the same conditions, which may be attributed to high total anthocyanin content in LRM-e mentioned above. Both dyed wool fabrics presented a stronger scavenging function on the hydroxyl radicals than superoxide radicals. 3.5. Enhanced effect of Fe ions treatment LRM-e-W and LRM-w-W samples with similar K/Smax values (about 4.80) were prepared through optimizing the dyeing process, and then treated with Fe2+ or Fe3+ ions (0.015 mmolL−1) as a post mordant at 60 °C for 30 min. After thoroughly rinsing and air drying, K/S curves of the treated samples (denoted as LRM-e-W-Fe2+ and LRM-w-W-Fe2+ for Fe2+ ion treating, LRM-e-W-Fe3+ and LRM-w-W-Fe3+ for Fe3+ ion treating) were measured and presented in Fig. 5(a and b). An obvious maximum adsorption peak was found at 530 nm in the K/S curves of both dyed wool fabrics, and both peaks showed similar K/ Smax values before Fe ions treating in Fig. 5(a and b). Both K/S curves dramatically changed and the peaks at 530 nm almost disappeared after Fe ions treating. This suggested that Fe ions treating caused a significant change in the color of both samples due probably to the interaction of anthocyanins with Fe ions. The previous works [39,40] confirmed that one of the main characteristics of anthocyanins is that they can coordinate with some metal ions such as Fe3+ or Mg2+ ions to form metal-anthocyanin complexes, thus changing their color. It was noticed that LRM-e-W-Fe3+ and LRM-w-W-Fe3+ showed more intensive K/S curves than LRM-e-W-Fe2+ and LRM-w-W-Fe2+, correspondingly. This demonstrated that Fe3+ ions reacted more easily with anthocyanins than Fe2+ ions, thus possibly depositing more anthocyanins on wool fabric. Specifically, treating with Fe ions, especially Fe3+ ions produced darker greener and yellower shades, indicated by lower a* (redness-greenness value) and c* (saturation), higher b* (yellownessblueness value). Increasing concentration of Fe ions could enhance this trend (Tables 1 and 2). Fig. 6 showed the results from SEM-EDX analysis of both LRM dyed wool fabrics before and after treating of Fe2+ or Fe3+ ions. The orderly arrayed scales were observed on the LRM dyed wool fiber, and four elements including C, O, N and S were identified for both LRM dyed wool fabrics in Fig. 6 (a1 and b1). It was noticed from Fig. 6 (a2, b2, a3 and b3) that the EDX results indicated that except the presence of four elements mentioned above, the Fe ions, especially Fe3+ ions treated samples had low content of Fe element. Besides, it was found from their SEM images that these scales seem to be not clear on the fiber after treating with Fe2+ ions. Particularly, the scales were covered by the mud-like layers, thus becoming more obscure after treating with Fe3+ ions. These finds revealed that Fe ions were immobilized on the LRM dyed wool fiber through a simultaneous coordination of Fe ions with adjacent OH groups in anthocyanin molecules and with carboxyl and amino in wool fiber [46,47], which will be responsible for the enhanced durability of the LRM dyed wool fabrics. A possible reaction mode was described in Scheme 1. More importantly, the antibacterial effects of both LRM dyed wool fabrics were investigated and compared before and after treating of Fe2+ or Fe3+ ions. The original wool fabric was also used in the control experiment to calculate the R% values of the fabric samples, and the results were presented in Fig. 5(c). It was observed that Fe ions treating increased R% values against two bacteria, and LRM-e-W-Fe3+ and LRM-w-W-Fe3+ had higher R% values than LRM-e-W-Fe2+ and LRM-wW-Fe2+, which indicated that Fe3+ ions treating more effectively enhanced antibacterial performance of the LRM dyed wool fabrics than Fe2+ ions treating. According to the work of Pansuriya and coworkers [41], the Fe(III) complexes exhibited higher activity than free ligands. A probable explanation for enhancement in antibacterial performance after Fe ion coordination may mainly be from Tweedy's chelation theory [42]. In general, chelation is able to significantly decrease the

3.6. Durability of LRM dyed wool fabrics The LRM dyed wool fabrics were subjected to the repeated washing to investigate the durability of their functionalities. LRM-e-W and LRMw-W samples with similar K/Smax values (about 4.80) were prepared and then treated with Fe2+ or Fe3+ ions (0.015 mmolL−1) at 60 °C for 30 min. The durability of antibacterial and antioxidant activities of the dyed wool fabrics was assessed before and after Fe ions treating by different washing cycles and listed in Table 3. Washing tests were conducted according to Chinese Standard: Textiles Test Specification for Color Fastness to Washing with Soap or Soap and Soda (GB/T39212008, ISO105-C10:2006, MOD). In brief, 2.0 g of LRM dyed wool fabric was placed into 100 mL of 5.0 gL-1 soap aqueous solution, and then continuously stirred for 30 min at 40 °C, which was regarded as one washing cycle. As seen from Table 3, increasing washing cycles caused a significant decline in inhibition% and R% values of the dyed wool fabrics before Fe ions treating. Specifically, inhibition% and R% values of LRM-e-W decreased to 53.3%, 68.0% and 31.9%, 46.8% respectively, after 10 washing cycles, but which were always higher than those of LRM-w-W, correspondingly. This may be due to the difference in anthocyanins content and their adhesion forces to wool fiber between both LRM extracts. As mentioned above, the treating of Fe ions, especially Fe3+ ions could increase functionalities, particularly antibacterial activity of the dyed wool fabrics. Importantly, Fe3+ ions treating obviously limited reduction extent of inhibition% and R% values after washing processes. The relatively high inhibition% (67.9% and 74.8%) and R% (79.7% and 81.3%) values were observed for LRM-e-W-Fe3+ after 10 washing cycles. These finds revealed that the treating of Fe ions, especially Fe3+ ions enhanced the durability of the LRM dyed wool fabrics, thus showing better functionalities after the repeated washing. A main reason for this was that Fe ions could link anthocyanin molecules and wool fiber by forming complexes expressed by Scheme 1. The washing fastness, rubbing fastness and light fastness of the dyed wool fabrics were examined to further understand their durability (Table 4). Both dyed wool fabrics showed the relatively high washing fastness and rubbing fastness rating of at least 3–4 on grey scale. However, a bad light fastness rating of 1 was observed for both samples. Treating with Fe ions, especially Fe3+ ions enhanced their three fastnesses, particularly light fastness, demonstrating that Fe ions could effectively reduce color change of anthocyanin compounds on wool fiber caused by washing, rubbing or light irradiation. 3.7. Comparison with dyed wool fabrics with Lycium Barbarum L. fruits extract Lycium barbarum L. (LBL) as a traditional Chinese herb has extensively been applied in Asian area for a long time, due to its healthenhanced functions for human body, especially anticancer and chronic diseases controlling. Carotenoids, flavonoids and polysaccharides were isolated and identified to be three main constituents of LBL fruits 315

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References

extract in the previous investigations [48,49]. In this present work, LBL water extract was prepared and then used for the dyeing of wool fabric by the same extraction and dyeing processes as LRM water extract. The antibacterial and antioxidant activities of the LBL dyed wool fabric (LBL-w-W) was then tested and compared with those of the LRM dyed wool fabric (LRM-w-W), and the results were summarized in Fig. 7. As shown in Fig. 7 (A), LBL dyed wool fabric had a different K/S curve from LRM dyed wool fabric, and its λvis-max was found to be 500 nm, which was less than that (530 nm) of LRM dyed wool fabric. This was due mainly to a big difference in chemical composition between LBL and LRM water extracts. The moderate antibacterial and antioxidant properties of LBL dyed wool fabrics were found in Fig. 7 (BC) because of their relatively high Inhibition% and R% values. A previous work [49] reported that the flavonoid compounds in LBL extract were active against both E. coli and S. aureus, thus, which may be responsible for the antibacterial performance of LBL-w-W. Other previous studies [48,50,51] investigated the antioxidant properties of LBL extract and revealed that carotenoids showed the most significant enhanced function on scavenging hydroxyl radicals owing to long chain of conjugated double bonds in their chemical structures. While keto and hydroxyl groups in flavonoids were effective in scavenging superoxide anion, and increasing number of hydroxyl groups favor their scavenging activity. Accordingly, the antioxidant activities of LBL-w-W may be closely associated with the carotenoid and flavonoid compounds in LBL water extract adsorbed on wool fabric. Comparing both dyed wool fabrics, it was obvious that Inhibition% and R% values of LBL dyed wool fabric were lower than those of LRM dyed wool fabric at the similar conditions, revealing stronger antibacterial and antioxidant activities of LRM-w-W than LBL-w-W. Similar phenomenon was observed by Zilic and coworkers [52], who isolated phenolic compounds, carotenoids, and anthocyanins from colored maize kernels, and reported that the darker colored maize showed better antioxidant ability, which was relative to its high content of total anthocyanins. Consequently, it was estimated that higher antibacterial and antioxidant activities of LRM-w-W were probably determined by the anthocyanins adsorbed on its surface.

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4. Conclusions LRM fruits could be extracted with ethanol and water, respectively to obtain the functional colorants, which were then identified and used for the functionalizing of wool fabric by an exhaustion dyeing process. LRM ethanol extract (LRM-e) was found to contain more anthocyanin compounds than LRM water extract (LRM-w), which was responsible for high color strength (K/S) of the dyed wool fabric with LRM-e. High temperature enhanced the adsorption of LRM extracts onto wool fabric. K/S values of LRM dyed fabrics gradually decreased with increasing pH level of the dyeing solution. LRM-e dyed wool fabric showed slightly better antimicrobial and antioxidant activities than LRM-w dyed wool fabric with similar K/S value. Increasing K/S value led to the enhanced antioxidant activities. Treatment of Fe ions, especially Fe3+ as the post mordant favored their antibacterial and antioxidant activities. Besides, both LRM dyed wool fabrics exhibited durable functionalities resistant to washing after Fe ions treatment. Compared with the dyed wool fabric with Lycium barbarum L. water extract, LRM-w dyed wool fabric had the strong functionalities at the similar conditions. Just for these valuable finds, the LRM dyed wool fabric can be considered as a promising healthy textile that meet the requirement for comfort, hygiene and wellbeing.

Acknowledgement This research was supported by Innovation & Pioneering Talents Plan of Jiangsu Province (2015-340). 316

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