Extraction of natural colorant from purple sweet potato and dyeing of fabrics with silver nanoparticles for augmented antibacterial activity against skin pathogens

Accepted Manuscript Extraction of natural colorant from purple sweet potato and dyeing of fabrics with silver nanoparticles for augmented antibacterial activity against skin pathogens

Palanivel Velmurugan, Jae-In Kim, Kangmin Kim, Jung-Hee Park, Kui-Jae Lee, Woo-Suk Chang, Yool-Jin Park, Min Cho, Byung-Taek Oh PII: DOI: Reference:

S1011-1344(17)30785-6 doi: 10.1016/j.jphotobiol.2017.07.001 JPB 10906

To appear in:

Journal of Photochemistry & Photobiology, B: Biology

Received date: Revised date: Accepted date:

8 June 2017 29 June 2017 3 July 2017

Please cite this article as: Palanivel Velmurugan, Jae-In Kim, Kangmin Kim, Jung-Hee Park, Kui-Jae Lee, Woo-Suk Chang, Yool-Jin Park, Min Cho, Byung-Taek Oh , Extraction of natural colorant from purple sweet potato and dyeing of fabrics with silver nanoparticles for augmented antibacterial activity against skin pathogens, Journal of Photochemistry & Photobiology, B: Biology (2017), doi: 10.1016/j.jphotobiol.2017.07.001

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ACCEPTED MANUSCRIPT Extraction of natural colorant from purple sweet potato and dyeing of fabrics with silver nanoparticles for augmented antibacterial activity against skin pathogens Palanivel Velmurugana, Jae-In Kima, Kangmin Kima, Jung-Hee Parka, Kui-Jae Leea, WooSuk Changb, Yool-Jin Parkc, Min Choa*, Byung-Taek Oha,d*

Division of Biotechnology, Advanced Institute of Environment and Bioscience, College of

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a

b

Department of Biology, University of Texas-Arlington, Arlington, TX 76019, USA

Department of Ecology Landscape Architecture-Design, College of Environmental and

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c

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54596, South Korea

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Environmental and Bioresource Sciences, Chonbuk National University, Iksan, Jeonbuk

Bioresource Sciences, Chonbuk National University, Iksan, Jeonbuk 54596, South Korea Plant Medical Research Center, College of Agricultural and Life Sciences, Chonbuk

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d

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National University, Jenoju, Jeonbuk 54896, South Korea

*Corresponding authors Min Cho Tel: +82-63-850-0845; Fax: +82-63-850-0834. E-mail: [email protected] Byung-Taek Oh Tel: +82-63-850-0838; Fax: +82-63-850-0834. E-mail: [email protected] 1

ACCEPTED MANUSCRIPT Abstract The main objective of this study was to extract natural colorant from purple sweet potato powder (PSPP) via a water bath and ultrasound water bath using acidified ethanol (A. EtOH) as the extraction solvent. When optimizing the colorant extraction conditions of the solvents, acidified ethanol with ultrasound yielded a high extraction capacity and color intensity at pH

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2, temperature of 80°C, 20 mL of A. EtOH, 1.5 g of PSPP, time of 45 min, and ultrasonic

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output power of 75 W. Subsequently, the colorant was extracted using the optimized

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conditions for dyeing of textiles (leather, silk, and cotton). This natural colorant extraction technique can avoid serious environmental pollution during the extraction and is an

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alternative to synthetic dyes, using less solvent and simplified abstraction procedures. The extracted purple sweet potato natural colorant (PSPC) was used to dye leather, silk, and

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cotton fabrics in an eco-friendly approach with augmented antibacterial activity by in situ synthesis of silver nanoparticles (AgNPs) and dyeing. The optimal dyeing conditions for

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higher color strength (K/S) values were pH 2 and 70°C for 45 min. The colorimetric

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parameters L∗, a∗, b∗, C, and H were measured to determine the depth of the color. The Fourier transform infrared spectroscopy (FTIR) spectra of undyed control, dyed with PSPC

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and dyed with blend of PSPC and AgNPs treated leather, silk and cotton fabric were investigated to study the interaction among fiber type, nanoparticles, and dye. The structural

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morphology of leather and silk and cotton fabrics and the anchoring of AgNPs with elemental compositions were investigated by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). The dry and wet rubbing fastness for dye alone and dye with nanoparticles were grade 4–5 and 4, respectively. Thus, the results of the present study clearly suggest that in situ synthesis of AgNPs along with dyeing should be considered in the development of antimicrobial textile finishes. Key words: Natural colorant; extraction; ultrasound; dyeing; textiles; antibacterial 2

ACCEPTED MANUSCRIPT 1. Introduction Presently, the usage of natural colorant is thriving worldwide as an alternative to synthetic colorant as an environmentally friendly method. During textile finishing, an enormous number of synthetic colorants have been utilized to dye fabrics; however, because all the colorant does not bind to the fabrics, 10-15% of the unbound synthetic colorant is

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released into the water stream, coloring the effluent and leading to environmental damage

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[1]. Also, many kinds of solvents and chemical intermediates are used in synthetic colorants

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for better binding, and these toxic chemicals can harm living beings through serious pollution and harm to the environment [1, 2]. While there are several techniques in development to

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treat synthetic colorants, they are all costly and time-consuming. To resolve this problem, the only alternative is eco-friendly natural colorants form plant sources, which are highly

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available, low cost, and environmentally friendly.

Extraction of colorant from various plant-based products due to the leaching process

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of solid and liquid is a critical issue [3]. Colorant extraction from tough plant cell membranes

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has been performed through various physical methods such as ultrasound for beetroot dye [47]; electric pulse and gamma ray irradiation extraction [8, 9] for green wattle bark, marigold

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flowers, pomegranate rinds, 4’o clock plant flowers, and cocks comb flowers [3]; and microwave-assisted extraction of yellow-red natural dye from the seeds of Bixa orellana [10].

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Among several methods, ultrasound is a novel technique to rupture the cell wall and release natural dye into the extraction medium. Therefore, we examined ultrasound extraction of sweet potato colorant using acidified ethanol along with ultrasound. Fabrics finished with natural dye have recently become attractive options due to their value-added

features

such

as

antimicrobial

and

antiallergenic

properties,

better

biodegradability, and environmental friendliness [11]. To meet the growing demand for natural dyes with potent antimicrobial properties for clothing, plant-based colorants and silver 3

ACCEPTED MANUSCRIPT nanoparticles (AgNPs) are the best potential choice for development and utilization because of their ease of availability, high productivity, low cost, and short production cycle [12, 13]. Textiles are known to be a great harbor of bacterial growth due to their large surface area and protein (keratin) and cellulose structures that enhance bacterial growth by providing basic moisture, oxygen, and nutrients and an ideal temperature [14], which lead to unpleasant odor,

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skin infection, low product quality and other related issues [15]. Hence, there is high demand

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for the development of excellent antibacterial textiles, clothing, and leather. Previously,

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several antimicrobial textiles have been developed and reported [16-21]. However, these current methods all produce non-biodegradable synthetic chemical compounds, which cause

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environmental and health concerns. Hence, there is a need to develop textiles such as cotton, silk, and leather dyed with natural dyes with an efficient antibacterial agent using AgNPs.

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Purple sweet potato has recently been suggested as a promising source of valuable natural colorant. Purple sweet potato contains abundance of phytochemical with rich

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nutritional value and its health benefits has attracted public to consume more, thus it being

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regarded as a functional food [22]. Since, its introduction from Japan and China, purple sweet potato has received a lot of attention because of its high content of anthocyanins [23] with a

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positive charge with C6-C3-C6 structure (cyanidin, peonidin, and pelargonidin) and one of the most common water-soluble pigments in nature [24]. Purple sweet potato anthocyanins

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were found to be quite stable and have good biological activities [22,25] In this study, we have studied two extraction techniques using water bath extraction and ultrasonication with water bath to extract purple sweet potato colorant (PSPC) with acidified ethanol and water as solvents. The extracted colorant with AgNPs was used to dye textiles, and the antibacterial activity against odor and skin bacteria was examined. Additionally, the dyed and AgNP-coated textiles and leather were subjected to FTIR and

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ACCEPTED MANUSCRIPT SEM-EDS analyses to identify functional groups and study the morphology of the anchored nanoparticles. 2. Materials and methods 2.1 Chemicals and media Silver nitrate (AgNO3) (99.9%) acquired from DaeJung Chemicals, Seoul, South

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Korea, was used for the synthesis of AgNPs. Commercial silver nano powder (99.5%, <100

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nm) was purchased from Sigma-Aldrich (St. Louis, MO, USA). Mueller-Hinton agar, brain-

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heart infusion broth (BHI), and Luria-Bertani broth (LB) were purchased from MB Cell, Seoul, South Korea, for the antibacterial study. All chemicals were used as supplied.

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Nanopure water (conductivity=18 µΩ/m, TOC < 3 ppb, Barnstead, Waltham, MA, USA) was used in all experiments.

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2.2 Sweet potato

A commercially available fine purple sweet potato (Ipomoea batatas (L.) Lam)

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powder was used to extract the purple colorant to dye textiles and optimize the extraction

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through conventional direct heating and conventional direct heating with ultrasonic-assisted extraction. To optimize the extraction, varying parameters of pH, temperature, time, solvent

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concentration, substrate concentration, and ultrasound were examined. 2.3 Textile materials

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Various textiles of scoured and bleached white cotton fabric (warp 106 dtex, weft 106 dtex; warp density 133 yarns per inch, weft density 72 yarns per inch; weight 106.6 g/m2), white silk taffeta fabric (16.5 g m−2), and wet-blue goat leather were purchased online in South Korea. Before the leather was dyed using the process developed by Sivakumar et al. and Velmurugan et al. [4,13], the chrome tanned wet-blue goat leather was cut into 5 x 5 cm pieces as per the SLTC official method of sampling and neutralized to pH 6.0–6.5 using 1% sodium formate and 1% sodium bicarbonate solution. Cotton and silk fabrics were treated 5

ACCEPTED MANUSCRIPT with commercial fabric washing detergent (5 g L−1) in a boiling hot water bath for 30 min, followed by several manual washes in running tap water and air drying at room temperature. 2.2 Methods 2.2.1 Extraction using a water bath and ultrasonication (water and acid–ethanol) Typically, 1.5 g of PSPP was placed in a 100-ml beaker, and 20 ml of distilled water

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or acid–ethanol (HCl, 1.5 mol/l) was added to two glass beakers. The beakers were covered

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using aluminum foil to avoid solvent loss during heating. The extraction was performed in a

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water bath and an ultrasonic water bath. To determine the optimal extraction conditions, water bath and ultrasonic extraction were carried out at different pH values (2-10) (HANNA

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HI 8424, HANNA Instruments, USA), liquid-solid ratios (1:20–1:50), solid–liquid ratios (0.25:1–1.50:1), temperatures (20–80°C) (water bath both), time intervals (0-60 min), and

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sonic powers (25-100 W) (SD-D400H, Sonics and Materials, South Korea). The extract was then centrifuged at 4000 rpm for 15 min and used for further analysis.

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2.2.2 Dyeing with and without silver nanoparticles on textiles

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The washed leather, silk, and cotton samples were immersed in PSPC aqueous solutions without nanoparticles or with a 1 mM AgNO3 solution to fabric ratio of 60:1. The

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dyeing of leather, silk, and cotton samples with and without nanoparticles was optimized for various parameters of pH (2-10), water bath temperature (40-80°C), dye concentration (1-

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10%), time (0-320 min), and sonic power (25-100W) at a fixed concentration of AgNO3 without any external chemicals. After the dyeing process, the fabrics were washed twice with boiling liquid soap, followed by drying at 70°C. All experiments were performed in triplicate. During the dyeing process, no moderant was used. For estimation of the silver nanoparticle and dye mixture, the control dye was used as a blank. Similarly, SEM-EDS analysis was performed to evaluate the number of nanoparticles anchored in the textiles and the elemental composition. 6

ACCEPTED MANUSCRIPT 2.3 Measurements 2.3.1 UV/visible scanning analysis of extracted colorant The purple colorant was extracted from the sweet potato powder with a 90% (V/V) acidified ethanol or water solution by adjusting various parameters for extraction optimization. The visible absorption spectrum of the dye solution was measured by a UV-Vis

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spectrophotometer (UV-1800, Shimadzu, Kyoto, Japan).

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2.3.2 Color characteristics

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The CIE L*, a*, b*, C*, h, - a* presents redness-greenness and b* presents yellowness-blueness, and the color strength (K/S) of dyed leather, silk, and cotton samples

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was tested using a Datacolor 600 spectrophotometer (Datacolor Company, USA) under illuminant D65, by a 10° standard observer. The test result was the average of the observed

K/ S =(1−R ) 2 / 2R ,

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2.3.4 Color fastness

(1)

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where R is the observed reflectance.

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values from eight different positions. The K/S value was calculated by Eq. (1):

The rubbing, washing, and light fastness of the dyed leather, silk, and cotton fabric

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samples were tested based on ISO 105-C01, ISO 105-X12, and ISO 105-B02, respectively. 2.3.5 FTIR and SEM-EDS analyses

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FT-IR spectra were produced by a Perkin-Elmer FTIR spectrophotometer (Norwalk, CT, USA) to confirm the functional groups of the PSPC in the control and dyed leather, silk, and cotton samples in diffuse reflectance mode at a resolution of 4 particles cm−1 in KBr pellets. For each sample, 32 scans at 4 cm−1 resolution (400–4000 cm−1) were gathered in transmittance (PSPP) or PSPC dyed textiles mode. Pieces of each control (undyed), dyed (only PSPC), and PSPC + AgNP dyed leather, silk, and cotton specimens were analyzed

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ACCEPTED MANUSCRIPT using SEM-EDS (JEOL-64000; JEOL, Tokyo, Japan) after coating the prepared fabric samples with osmium plasma. 2.4 Antibacterial activity The antimicrobial activity of control (undyed), dyed (only PSPC), and PSPC + AgNP dyed leather, silk, and cotton specimens were evaluated against four types of bacteria known

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to cause body odor or skin infections: B. linens (KACC-14346), P. acnes (KACC-11946), B.

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cereus (KACC-10001), and S. epidermidis (KACC-13234). These cultures were obtained

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from KACC (Korean Agricultural Culture Collection). The microbial cultures were preserved in a nutrient agar medium and stored at 4ºC for further use.

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The four strains of odor- and skin infection-causing bacteria B. linens, P. acnes (anaerobic condition), B. cereus, and S. epidermidis were applied to test the antibacterial

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properties of control (undyed), dyed (only PSPC), and PSPC + AgNP dyed leather, silk, and cotton specimens according to Ren et al., [11] and Hashemikia et al., [26]. Briefly, all four

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bacteria were cultured, and the cells were centrifuged, washed, and suspended in normal

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saline to an OD620 of 0.1, which is equal to 1.5 × 108 CFU/mL. Control (undyed), dyed (only PSPC), and PSPC + AgNP dyed leather, silk, and cotton specimens with equal dimensions

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were separately cut into small pieces (~ 1 × 1 cm), placed in sterile 50 mL autoclavable Falcon tubes, and sterilized in an autoclave. The samples were then inoculated with each

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bacteria individually, with aerobic and anaerobic conditions maintained for the appropriate organism throughout the entire study, and incubated at 30 and 37°C for 1-5 d according to the specific organism. After the proper exposure time, the cultures were diluted with normal saline, and 0.1 mL of each dilution was spread on Mueller–Hinton agar. Plates were incubated for the appropriate time and at the optimal temperature for each organism. After the antibacterial experiment, the bacteria colonies were counted by a colony counter, and the reduction in bacteria was obtained according to Eq. (2): 8

ACCEPTED MANUSCRIPT R(%) = (A−B)/A × 100%,

(2)

where R is bacterial reduction (%), A and B are the number of visual bacterial colonies from undyed control (undyed), dyed (only sweet potato dye), and dye + silver nanoparticle dyed leather, silk, and cotton specimens, respectively. 2.5 Data analysis

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Statistical analysis was performed using the procedures of the Statistical Analysis System.

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3. Results and discussion

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Currently, plant-based pigments or colorants of various classes and types including anthocyanins, carotenoids, betalains, and chlorophylls have been used as food additives,

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textile colorings, and in livestock feed, pharmaceuticals, cosmetics, and other applications [11, 27]. Plant-based pigments or colorants are classified as either fat-soluble pigments that

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exist in the plastids of plant protoplasm (protoplasts), chlorophylls, and carotenoids or watersoluble pigments including anthoxanthins (common flavonoids) and anthocyanins, which are

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dissolved in the cell sap [1, 27-29]. Anthocyanins can change color from red to blue to green

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based on pH and are responsible for the appearance of color in plant parts such as roots, flowers, and fruits [30]. There are various types of anthocyanins that have many biomedical

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applications such as decreasing the risk of cancer [31], modulating the immune response [32], reducing inflammatory insults [33], and functioning as natural antimicrobial agents [14, 34].

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Fan et al. [28] reported that PSP contains a high level of anthocyanins compared to white, yellow, and orange sweet potatoes, and the contents differ depending on variety. The amount and stability of the anthocyanins present in PSP and available during the extraction process depend on extraction parameters such as pH, temperature, type of solvent, and time (Fig. 1). 3.1 Dye extraction (direct water bath and ultrasonication) 3.1.1 Effect of pH

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ACCEPTED MANUSCRIPT The effect of pH on extraction of PSP dye by ultrasonic power water bath heating and conventional water bath heating are presented in Fig. 2a & b, respectively. These figures show the absorbance spectra at λ max (550 nm) with conventional heating and heating with ultrasound extraction at different pHs. An alkaline condition of pH 2 was optimal for the extraction of dye using both conventional and ultrasound water bath methods. At pH 2.0, the

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anthocyanin-based extract was red, and the λ max was observed at 550 nm (Fig. 2a and b),

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suggesting that the anthocyanins predominantly existed in the form of flavylium cations [35].

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Above pH 2, the color of the dye from moderate to low pH to high pH with no uniform absorbance peaks due to the anthocyanin can occur as a mixture of four equilibrium forms

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including flavylium cation (red), quinonoidal base (purple), carbinol base (colorless), and chalcone (yellow) [35, 36].

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3.1.2 Effect of temperature

Fig. 2c and d show the extraction of PSPC by ultrasonic power with bath heating and

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conventional water bath heating using different temperatures. The ultrasonic bath at 80°C and

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water bath at 90°C were optimal, showing the highest absorbance values. The absorbance spectrum of the extract was red with a λ max at 550 nm (Fig. 2c and d), which shows that the

temperature.

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dye can withstand higher temperatures, supporting the possibility of dyeing at high

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3.1.3 Effect of A. EtOH concentration Experiments were conducted using acidified ethanol as a solvent for PSPC. Acidified ethanol was selected as an extraction solvent based on a previous report by Li et al. [37] which showed that acidified ethanol yielded a maximum extraction of about 80% from PSPC and had few environmental hazards. Different solvent concentrations were used for extraction purposes with optimized pH and temperature. The results show that 20 mL and 30 mL of acidified ethanol were sufficient to extract 1 g of PSPC by an ultrasonic bath (Fig. 2e) and 10

ACCEPTED MANUSCRIPT water bath (Fig. 2f), respectively. The ultrasonic bath at 80°C and water bath at 90°C were optimum, with the highest absorbance values. The absorbance spectrum of the extract was red with the λ max at 550 nm (Fig. 2e and f), indicating that the dye can be extracted with a minimal amount of A. EtOH, which is sufficient to minimize pollution. Finally, the ultrasound extraction resulted in the maximum color extraction yield.

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3.1.3 Effect of substrate concentration

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Optimal conditions for pH, temperature, and A. EtOH were used to determine the

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ideal substrate amount for a high yield of color from PSPC (Fig. 3a and b). Different amounts of PSPC were used for both ultrasonic and water bath extraction among all 1.5 g/10 mL of

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substrate yields for maximum color extraction. The absorbance spectrum of the extract was red with the λ max at 550 nm for the ultrasonic bath and water bath (Fig. 3a and b). Finally,

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the minimum amount of 1.5 g was set as an optimum extraction amount. 3.1.4 Effect of extraction time

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The optimal conditions of all above-mentioned parameters were fixed to determine

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the ideal time for maximum color extraction from PSPC by an ultrasonic bath and water bath (Fig. 3b and c). An extraction time of 45 min (Fig. 3c) or 75 min (Fig. 3d) was essential for

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the maximum yield of color from PSPC by an ultrasonic bath and water bath, respectively. This result suggests that an ultrasonic bath is best for extraction of color from PSPC. The

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absorbance spectrum of the extract was red with the λ max at 550 nm for the ultrasonic bath and water bath (Fig. 3c and d). These results indicate that the extraction starts at 30 min and marginally increases up to 45 or 90 min for the ultrasonic bath and water bath, respectively. 3.1.5 Effect of sonic output power The effect of varying the ultrasonic power from 25 to 100 W on the extraction was examined for extracting color from PSP. The total extract yield as well as colorant yields for the different power outputs are shown in Fig. 3e. According to the results, the maximum total 11

ACCEPTED MANUSCRIPT yield of extract was obtained at a power output of 75 W. Higher ultrasonic power could cause degradation of substances [3]. Considering this, 75 W of power output from the sonicator is better suited for the extraction of PSPC under the given process conditions. The absorbance spectrum of the extract was red with the λ max at 550 nm for the ultrasonic bath and water bath (Fig. 3e). The color stability was found to be excellent, and there was no adverse effect

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of the higher ultrasonic intensity employed for the extraction process.

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3.1.6 Optimization of the dyeing process

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To investigate the color changes in PSPC dyed leather, silk, and cotton samples at different pH values under ultrasonic power, the plot of maximum K/S as a function of

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concentration of the dye solution corresponding to different modes of dyeing parameters are given in Fig. 4a. The pH was adjusted from 2 to 10 to reflect the different colors expressed in

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the dyed leather, silk, and cotton samples both without AgNPs (dye alone) and with AgNPs (dye + AgNPs) (Fig. 4b). The AgNPs were in situ synthesized on leather, silk, and cotton

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fabrics under ambient conditions. There was not much difference in the colors with and

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without AgNPs, which might be due to the high color strength of the PSP dye (Fig. 4b). As evident in Fig. 4b, the leather, silk, and cotton fabrics treated at different pH values gradually

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changed to pink, light pink, light green, and dark green from low pH to high pH. As shown, the maximum K/S value increased from 0.12 to 1.89 when the pH of the dye solution

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increased from pH 2 to 5, while the K/S values decreased in the leather, silk, and cotton fabrics with in situ synthesized AgNPs. This might be due to the overcrowding of dye molecules inside the leather, silk, and cotton fabrics due to the ultrasonic power. The results indicate that the color strength of the leather, silk, and cotton fabrics treated with PSP dye can be tuned by controlling the pH. According to Kamel et al. [38], the correlation between dye structure and the leather, silk, and cotton fabrics can be attributed to the dye bath pH. Since the PSP dye used is a water-soluble dye containing anthocyanins [35], mainly glycosylated 12

ACCEPTED MANUSCRIPT cyanidin and peonidin, it would interact with the protonated terminal amino groups of the fabrics at acidic pH via an ion exchange reaction. Fig. 4c and d demonstrate the K/S value and color strength of the leather, silk, and cotton fabrics dyed with PSPC and PSPC with AgNPs under ultrasonic power at different temperatures. The results show that silk and cotton fabrics dyed with only PSP dye but no

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AgNPs show maximum K/S values of 1.80 and 1.762 at 70°C, respectively (Fig. 4c).

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However, cotton and silk fabrics with dye and in situ synthesized AgNPs show K/S values of

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1.52 and 1.46, respectively. These lower K/S values might be due to the overcrowding of dye molecules, which would prevent the nanoparticles from anchoring on the fabric (Fig. 4d). For

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leather, the maximum K/S values of 1.36 only with dye and 1.22 with dye and AgNPs might be because the tough muscle fiber might not allow the dye and nanoparticles to enter the

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leather matrix. The highest K/S values at 70°C might be due to swelling of the fiber, which will enhance the dye uptake.

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Fig. 5a and b show that the effect of dyeing time was conducted at a fixed concentration of

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PSP dye and optimized pH and temperature to reveal the effect of time for higher dye-uptake with dye alone and with dye and AgNPs by leather, silk, and cotton fabrics. As shown in Fig.

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5a, the color strength increased as the time increased in dye alone and in dye and AgNPs (Fig. 5a). A plateau is attained after 30 min until 45 min, which started to decline slightly

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with the prolongation of time (Fig. 5b). The decline in the dye ability can be attributed to desorption of dye molecules because of the long dyeing time. Fig. 5c and d show the effect of ultrasonic power on the dyeability of leather, silk, and cotton fabrics with PSP dye at different power levels (25–100 W). As shown in Fig. 5c, the color strength of dyed fabrics seemed to be directly proportional to the power supplied (Fig. 5d). This behavior again emphasizes the assisting effect of ultrasonic power on the dyeability of leather, silk, and cotton fabrics with the PSP dye alone or with AgNPs. As suggested 13

ACCEPTED MANUSCRIPT before [34], this can be explained by the uniform dispersion of dye molecules in the dye bath by breaking high molecular weight aggregates, ejection of filled gas molecules inside the fabrics from the fibers into the dye bath to create an additional cavitation to facilitate dye– fiber contact, and diffusion (fast-tracking the rate of dye dispersal inside the fiber by penetrating any insulating layer covering the fiber and accelerating any interaction or

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chemical reaction between the dye and fiber).

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3.1.7 Color coordinates

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CIELab values of leather, silk, and cotton fabric samples dyed with PSPC and PSPC with AgNPs under ultrasonic power are given in Table 1. The K/S plot (Fig. 4 and 5) showed

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that pH 2, bath temperature 70°C, time 45 min, and 75 W ultrasound show higher K/S values than controls, and the highest color strength was observed with these optimized conditions for

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PSPC and PSPC with AgNPs dyed samples. This can be attributed to the complex formation among fiber, dye, and AgNPs. The lightness (L*) values were higher in cases of dyed

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samples at non-optimum conditions and corresponded to lighter shades. In contrast, the L*

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values were lower in cases of optimum dyed samples along with AgNPs, which corresponded to deeper shades. In this study, no external chemicals were used for dyeing such as chemical

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moderants. 3.1.8 Color fastness

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Color fastness including rubbing (wet and dry), washing, and light fastness of the dyed leather, silk, and cotton fabric samples dyed with PSPC and PSPC with AgNPs using ultrasonic power with the optimum dyeing process is shown in Table 2. Since the floating color was adequately removed by washing twice with boiling soap liquid, the rubbing and washing fastness of the dyed cotton were good. However, the color fastness of alkali perspiration was scored as 4 (relatively good) due to the color sensitivity to pH [11]. The purplish-red PSPC changed color to become lighter and eventually became orange-yellow 14

ACCEPTED MANUSCRIPT with an increase in pH value, so the dyed leather, silk, and cotton fabrics were slightly lighter under alkali perspiration. 3.1.9 FTIR The infrared spectra of sweet potato pink dye for coloring of fabric materials (leather, silk, and cotton fabrics) mediated with and without AgNPs indicated functional groups in the

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range from 4000 cm-1 to 400 cm-1, which are shown in Fig. 6. The PSP dye extract exhibited

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OH group stretching vibrations at 3294 cm-1, C – H vibrations of CH3 and CH2 groups at 2931 cm-1, C=O stretching vibrations at 1727 cm-1 and 1633 cm-1, and C – O vibrations in the

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range of 1015 cm-1 to 775 cm-1. The fabrics without coloring exhibited OH and NH stretching

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vibrations indicating H bonding at 3317 cm-1, 3331 cm-1, and 3283 cm-1 and CH stretching vibrations at 2923 cm-1, 2900 cm-1, and 2927 cm-1, while C=O stretching vibrations were

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present in the leather and silk material in the range of 1632 cm

-1

to 1618 cm -1. At the same

time, C-N-C bending vibrations, C-O stretching vibrations, and C-H bending vibrations were

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recorded in the fabricated materials [13, 39]. Dyeing of leather, silk, and cotton fabrics

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exhibited OH and NH stretching, CH stretching, CH groups, C=O stretching, C-N-C vibrations, and C-O stretching vibrations. The major difference between the fabric material

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with and without coloring was the C-H bending vibrations, which were not found in pink dye-colored fabric materials, as shown in Fig. 6. The coloring of pink dye mediated AgNPs to

3278 cm

-1

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exhibit the formation of functional groups with minor peaks of 2924 cm -1, 3333 cm -1, and in the AgNP-coated fabric materials. All corresponding FTIR spectra peaks are

like earlier reports [40, 41]. 3.1.10 SEM-EDS The surface morphologies of the control dye alone, and dye with AgNP-treated fabrics are given in Fig. 7 a, b and c with the corresponding EDS pattern. Untreated fabrics showed smooth surfaces (Fig. 7a), whereas the surfaces of AgNP-treated fabrics showed 15

ACCEPTED MANUSCRIPT roughness due to deposition of AgNPs (Fig. 7a, b and c). Moreover, the high magnification SEM image (Fig. 7c) shows the uniform distribution of AgNPs on the surfaces of leather, silk and cotton fabrics. EDS analysis showed no silver in the untreated sample (Figs. 7a and b). The presence of AgNPs in the treated fabric was further confirmed by EDS analysis. 3.1.11 Antibacterial assay (minimum bactericidal concentration)

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The anti-bacterial properties of the control, dye alone, and dye with AgNP-treated

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fabrics were tested against B. linens, P. acnes, B. cereus, and S. epidermidis as the most

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common odor- and skin infection-causing bacteria. The percentages of bacterial reduction by control, dye alone, and dye with AgNP-treated fabric samples are reported in Table 3.

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Comparing the anti-bacterial properties of control and dye with AgNP-treated fabric samples indicated that the dye has lower antibacterial properties against B. linens, P. acnes, B. cereus,

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and S. epidermidis than dye with AgNPs, which showed good anti-bacterial efficiency. 4. Conclusion

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In this study, a novel method of dyeing leather, silk, and cotton fabrics with PSPC and

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PSPC with AgNPs was developed to enhance the antibacterial activity of the fabric. The optimum methods for the extraction of dye from PSP and the dyeing process were obtained.

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The dyed fabrics with PSPC and PSPC with AgNPs possessed good rubbing, washing, and perspiration fastness. In addition, the antibacterial activity of dyed fabrics with PSPC and

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AgNPs against B. linens, P. acnes, B. cereus and S. epidermidis was outstanding. This study demonstrates that natural colorants extracted from vegetables could be successfully employed as an effective, eco-friendly, and cleaner alternative to synthetic colorants in the textile dyeing industry. It can be concluded that, the use of eco-friendly ultrasound-assisted dyeing of textiles with PSPC is a very promising concept as an alternative method to synthetic dyeing. It may help to protect environment from pollution and potential to produce environmental friendly textile materials. On the environmental protection perspective and the 16

ACCEPTED MANUSCRIPT additional antibacterial properties of the textiles dyed with natural dye from PSPP, it can be applied as commercial natural colorant and will open a new avenue in future natural dye market. Acknowledgements This work was supported by Korea Institute of Planning and Evaluation for

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Technology in Food, Agriculture, Forestry and Fisheries (IPET) through Agri-Bio Industry

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Technology Development Program, funded by Ministry of Agriculture, Food and Rural

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Affairs (MAFRA) (315033-3). This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries (IPET) through Agri-

and Rural Affairs (MAFRA) (313058-5).

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Figure Legends

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Fig. 1 Purple sweet potato, purple sweet potato powder, and purple sweet potato color

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extraction with and without ultrasonication using acidified ethanol and the basic structure

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of the anthocyanin colorant.

Fig. 2 (a-f) Optimization of purple sweet potato colorant extraction. (a) (b) pH, (c) (d)

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temperature, and (e) (f) A. EtOH (acidified ethanol) using an ultrasonic water bath and normal water bath, respectively.

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Fig. 3 (a-d) Optimization of purple sweet potato colorant extraction. (a) (b) PSP concentration, (c) (d) time frame, and (e) ultrasonic power using an ultrasonic water bath

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and normal water bath, respectively.

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Fig. 4 (a-d) Optimization of dyeing of leather, silk, and cotton fabrics with PSPC and PSPC with AgNPs at different pH (a, b) and temperature (c, d).

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Fig. 5 (a-d) Optimization of dyeing of leather, silk, and cotton fabrics with PSPC and PSPC with AgNPs using different time frames (a, b) and ultrasonic power (c, d).

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Fig. 6 FTIR of leather, silk, and cotton fabrics dyed with PSPC and PSPC with AgNPs along with undyed control fabrics. Fig. 7 (a-c) SEM-EDS images of (a) leather, (b) silk, and (c) cotton fabrics dyed with PSPC and PSPC with AgNPs along with undyed control fabrics after five washing cycles.

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ACCEPTED MANUSCRIPT Table 1. CIE L,a,b values of the PSPC dyed leather, silk and cotton fabrics at optimum condition – Control, with and without AgNPs. L*

b* c* Control 10.23 22.21 32.21 10.23 5.22 5.21 2.64 6.32 5.31 5.33 2.89 5.38 Purple sweet potato colorant dyed 10.23 56.23 31.02 30.21 22.22 68.52 28.24 26.22 25.31 69.34 29.24 25.36 Purple sweet potato colorant dyed + AgNPs 10.23 65.21 26.84 31.0 22.22 70.21 22.56 28.42 26.31 76.25 23.59 28.68

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h° 32.52 20.21 20.32 56.32 52.84 58.36

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Table 2. Fastness properties of PSPC dyed leather, silk and cotton fabrics at optimum condition – Control, with and without AgNPs. Control

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Leather Silk Cotton

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Wet 3 2-3 3 3 3 4 Purple sweet potato colorant dyed 3 3 2-3 4 4-5 4 4-5 4-5 4 Purple sweet potato colorant dyed + AgNPs 3 3 2-3 4 4 4 4 4 4

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Dry 3 2 2

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ACCEPTED MANUSCRIPT Table 3. Antibacterial properties of PSPC dyed leather, silk and cotton fabrics at optimum condition – Control, with and without AgNPs. P. acnes B. cereus S. epidermidis Control (Bacterial reduction %) Leather Silk Cotton Purple sweet potato colorant dyed (Bacterial reduction %) Leather 52 31 46 34 Silk 74 71 62 52 Cotton 76 76 66 51 Purple sweet potato colorant dyed + AgNPs (Bacterial reduction %) Leather 68 43 58 46 Silk 86 82 74 61 Cotton 82 84 88 79

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ACCEPTED MANUSCRIPT Highlights  Extraction of natural colorant from purple sweet potato powder  Optimization of colorant extraction by different environmental parameters  Dyeing of textiles (leather, silk, and cotton) using extracted colorant and AgNPs

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 Augmented antibacterial activity of dyed and AgNPs coated leather, silk, and cotton

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