Journal of Science: Advanced Materials and Devices (2018) 175e180 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Electrospun characteristics of gallic acid-loaded poly vinyl alcohol fibers: Release characteristics and antioxidant properties P Chuysinuan a, T Thanyacharoen b, S Techasakul a, **, S Ummartyotin b, * a b Laboratory of Organic Synthesis, Chulabhorn Research Institute, Bangkok, Thailand Materials and Textile Technology, Faculty of Science and Technology, Thammasat University, Patumtani, Thailand a r t i c l e i n f o a b s t r a c t Article history: Received March 2018 Received in revised form 16 April 2018 Accepted 20 April 2018 Available online 27 April 2018 The physico-chemical properties of electrospun polyvinyl alcohol (PVA) based hydrogel composites were investigated Tetraethyl orthosilicate (TEOS) was employed as a crosslinking agent 2.5e7.5 wt% of gallic acid was successfully loaded into an electrospun poly vinyl alcohol fiber The resulting gallic acid loaded electrospun fiber based hydrogel presented a thermal resistance up to 200 C The structural properties, which were evaluated using FTIR and DSC, showed a good miscibility between the gallic acid and the polyvinyl alcohol With the increment on gallic acid, the diameter of the electrospun fibers increased The release profile of the electrospun fibers was investigated based on a diffusion method The electrospun fibers showed high antioxidant activities, which were monitored using DPPH, radical scavenging, ABTS,ỵ radical scavenging assay, and ferric reducing antioxidant power (FRAP) They also exhibited their good characteristics as a drug delivery system, and for use in wound healing and cosmetics © 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: Gallic acid Poly vinyl alcohol Electrospun Antioxidant Introduction In recent years, the development of electrospun nanofibers has been extremely demanded due to the excellence in biomedical research, owing to their high porosity and specific surface area Utilization of the electrospun nanofibers has provided a great interest in textile technology, tissue engineering, and would dressing, as well as a drug delivery system Electrospinning was therefore referred to as a fiber production technique It employed an electric force to draw charges threads of polymer solution and polymer melts up to the nano-scale fibers [1,2] Utilization of the electrospinning technique has therefore captured the interest in nanoscale fiber formation From a fundamental point of view, electrospinning was regarded as a well-known and versatile technique to fabricate fiber materials This technique has also gained many interests for making composite fibers, porous structure fibers, polymer fibers and so on This technique provided significant advantages such as high surface area to volume ratio, ease of fiber * Corresponding author ** Corresponding author E-mail addresses: supanna@cri.or.th (S Techasakul), sarute.ummartyotin@gmail com (S Ummartyotin) Peer review under responsibility of Vietnam National University, Hanoi functionalization, ease of material combination, ease of fiber deposition onto other substrate fibers, as well as a relatively low cost of the mass production process [3,4] Our research group has successfully developed the hydrogel composites for a drug delivery system [5e7] Utilization of hydrogel based materials was strongly demonstrated to achieve low toxicity, low immunogenicity and improved compatibility It was therefore remarkable to note that the utilization of the hydrogel based materials was versatile in various research sectors, including food technology, medical device, pharmaceutical technology, as well as cosmetics [8e10] In order to use the hydrogel based materials in medical technology with higher efficiency, the development of phenolic acid grafted hydrogels was considered as one of the most important approaches for its bioactivity [11] The phenolic grafted hydrogel was successfully prepared by a chemical coupling technique, the enzyme catalyzed method, the free radical mediated grafting method, as well as the electrochemical technique [12e15] An example of phenolic acid was referred to as coumaric acid, caffeic acid, ferulic acid and sinapic acid as suggested by Aludatt et al [16] The significant enhancement in the phenolic acid loaded hydrogel was due to its non-cytotoxicity, antioxidant activity, antimicrobial activity, antitumor activity, anti-allergic activity, as well as anti-diabetic activity To use the phenolic loaded hydrogel with higher efficiency, the development of materials in the nano-fibers form was therefore https://doi.org/10.1016/j.jsamd.2018.04.005 2468-2179/© 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) 176 P Chuysinuan et al / Journal of Science: Advanced Materials and Devices (2018) 175e180 proposed In 2013, Bosworth et al [17] reported on state of the art of the composite prepared from an electrospun fibers based hydrogel The application was very versatile in medical technology sector, such as regenerative medine, drug delivery system, as well as chemical sensor Han et al [18] and Zhang et al [19] also developed electrospun fibers for protein release based on emulsion technique The utilization of the electrospun hydrogel was also strongly evident in a scaffold based material as reported by Liu et al [20] Recently, the electrospun hydrogel was also extented to bio-based materials Mendes et al [21] and Bosiger et al [22] reported hybrid electrospun chitosan and phospholipids for transdermal drug delivery and antimicrobial treatment Therefore, we wish to extend our research work on hydrogel based composites in drug delivery The objective of this research work is to utilize the electrospinning technique, in order to prepare electrospun gallic acid-loaded poly vinyl alcohol based composite fibers Physico-chemical properties of the materials were therefore evaluated Their antioxidant properties and in vitro release characteristics were then tested and reported Experimental 2.1 Materials Poly vinyl alcohol (molecular weight 100,000) were purchased from chemical-supply Pty Ltd, Australia Tetraethyl orthosilicate (TEOS) and gallic acid (GA) were purchased from Sigma Aldrich, USA They were employed as a crosslinking agent and a bioactive compound, respectively Phosphate Buffered Saline (PBS) was purchased from VWR Cief Science Amresco, USA Acetic acid was purchased from Labscan, Thailand All of the chemical reagents were used as received without further purification 2.2 Methods 2.2.1 Preparation of Neat and Gallic Acid-Loaded polyvinyl alcohol Fiber Mats For preparing electrospun polymer matrix fibers, the 10% w/v of polyvinyl alcohol (PVA) was dissolved in DI water and heated at 80 C Subsequently, 2.5, 5, 7.5 %wt of gallic acid (GA) (based on weight of PVA) were added into PVA solution The mixture was stirred for h at room temperature to achieve a homogeneous solution The electrospinning system, equipped with a high voltage power supply unit under a fixed electric field of 15 kV/15 cm, was used to provide high voltage The positive electrode with a high voltage power was connected to the needle tip Aluminum foil wrapped around the drum collector 2.2.2 Total phenolic content Analysis of total phenolic contents of the GA/PVA electrospun fibers was determined based on Folin-Ciocalteau test [23] The 2.5, 5, 7.5% PVA/GA electrospun fibers were immersed in water for h and then the solution was reacted with N folin & ciocalteu's phenol reagent solution and vortexed immediately After that, 7%w/ v Na2CO3 solution was added to this mixture The mixture was shaken and left to incubate for h and absorbance was measured using a microplate reader at 765 nm Gallic acid was used as standard, and the total phenolic content was expressed as mg gallic acid equivalent per gram of sample (GAE/g extract) 2.2.3 Antioxidant activities The antioxidant activities of the GA/PVA electrospun bers were monitored using DPPH radical scavenging, ABTSỵ radical scavenging assay, and Ferric reducing antioxidant power (FRAP) a DPPH, radical scavenging assay DPPH, radical scavenging activity of 2.5, 5, and 7.5% of GA/PVA electrospun fibers was determined according to the method of Pang et al [24] The reaction mixture consisted of the sample and 0.3 mM of DPPH radical solution in methanol The mixture was kept in the dark for 30 The absorbance of the reaction mixture was then measured using a microplate reader at a wavelength of 517 nm The scavenging activity (%) was calculated as follows: Scavenging activity%ị ẳ Ablank Asampleị 100 Ablank where Ablank and Asample are the absorbance values of the blank solution (0.3 mM DPPH solution) and the sample solution, respectively b ABTS,ỵ radical scavenging assay The ABTS,ỵ radical cation scavenging capacity of the GA/PVA electrospun fibers was determined according to the procedure described by Finley et al [23] The ABTS,ỵ radical cation solution was obtained from the reaction of 2.6 mM potassium persulfate in water with 7.4 mM ABTS,ỵ in methanol for 12 h in the dark The stock solution was diluted with methanol to obtain an absorbance of 0.7 ± at 734 nm with a microplate reader Then, sample release solutions, obtained from 2.5, 5, and 7.5% GA/PVA electrospun bers immersing in water, were reacted with ABTS,ỵ solution and incubated for h ABTS,ỵ radical scavenging capacity was calculated using the following formula: Scavenging activity%ị ẳ ðAblank À AsampleÞ Â 100 Ablank where Ablank is the absorbance of the ABTS,ỵ radical without the antioxidant materials and Asample is the absorbance of the ABTS,ỵ radical in the presence of the antioxidant materials after h c Ferric reducing antioxidant power (FRAP) The antioxidant capacity of 2.5, 5, and 7.5% GA/PVA electrospun fibers was estimated spectrophotometrically following the procedure of Yang et al [25] The Ferric reducing antioxidant power (FRAP) reagent was prepared by mixing acetate buffer, 2,4,6-tri(2-pyridyl)-S-triazine (TPTZ) solution TPTZ in HCl and FeCl3 in the proportion of 10:1:1 Freshly prepared working FRAP reagent was pipetted using micropipette and mixed with the solution An intense blue color complex was formed when ferric tripyridyl triazine (Fe3ỵ TPTZ) complex was reduced to ferrous (Fe2ỵ) form and recorded at 593 nm against a reagent blank (FRAP reagent) The calibration curve was prepared by plotting the absorbance at 593 nm versus known concentrations of FeSO4 and Trolox was used as the positive control The reducing power was expressed as mg of Trolox equivalent per gram of sample (mg TE/g extract) All the determinations were performed in triplicates d In vitro gallic acid release study The electrospun fibers of PVA with different GA concentrations were cut into circular shape with 1.5 cm diameter pieces and the initial weight was measured Each specimen was then placed in a tube containing 30 mL phosphate buffer saline solution (PBS) The tubes containing the solutions were then incubated in a shaking water bath at 37 C ranging between and 2880 The medium P Chuysinuan et al / Journal of Science: Advanced Materials and Devices (2018) 175e180 solution was removed, the fresh medium with equal amount was replaced, and the amount of GA release from the GA/PVA electrospun fibers was measured using a microplate reader by measuring the absorbance at 260 nm 2.3 Instruments The surface morphology was determined using scanning electron microscope (JEOL JSM-6400) The samples were cut into circular shape with an average diameter of 1.5 cm Specimens were coated with a thin gold layer using a sputter The fiber diameters were measured using a SemAphore 4.0 software at 20000Â magnification More than 50 individual fibers were measured for their diameters and reported as mean ± SD The chemical structure was determined by Fourier transform infrared (FT-IR) spectrophotometer (SPECTRUM ONE, Perkin Elmer) Samples were scanned over range of 400e4000 cmÀ1 at room temperature and attenuated total reflectance (ATR) mode at a resolution of cmÀ1 Thermal stability was evaluated by thermo gravimetric analysis (209 F3 Tarsus, NETZSCH) The samples were heated from room temperature to 700 C with a heating rate of 10 C/min under nitrogen atmosphere Thermal behavior was investigated using a differential scanning calorimeter (204 F1 Pheonix) under nitrogen atmosphere The samples were heated from room temperature to 300 C at a heating rate of 10 C/min A Varian Cary 5000 UV-Vis NIR spectrophotometer (Agilent Technologies, CA, USA), equipped with a transmittance accessory, was employed to record the electronic spectrum of the samples in the wavelengths of 200e900 nm This technique allowed the absorbance spectra of the samples to be studied The accessory consisted of a 110-nm diameter integrating sphere and an in-built high-performance photomultiplier Each sample was placed in a sample cell, which was specifically designed for the instrument A baseline was recorded and calibrated using a polytetrafluoroethylene (PTFE) reference cell Results and discussion Electrospun characteristics of the GA/PVA electrospun fibers were successfully conducted Fig exhibits the FTIR spectra of the GA/PVA electrospun fibers Note that at a wavenumber of 3400 cmÀ1, it was attributed to the characteristic peak of OeH and NeH [26] Furthermore, it was found that the electrospun poly vinyl alcohol exhibited the CeH stretching vibration at approximately 2930 cmÀ1 It was slightly shifted to a higher wavenumber when the gallic acid was loaded into the electrospun fibers It was Fig FTIR spectra of the gallic acid-loaded electrospun poly vinyl alcohols 177 obviously observed that the characteristic peak at 1710 cmÀ1 was due to the C]O stretching vibration of the carboxyl group from the poly vinyl alcohol [27] The peak of the OeH bending vibration was observed at 1250 cmÀ1 [28] Meanwhile, the characteristic peaks of the electrospun fibers from 500 to 1000 cmÀ1 did not show obvious changes in their functional groups The thermal behavior of the GA/PVA electrospun fibers was investigated through the thermal gravimetric analysis Fig shows the thermal decomposition characteristic of the GA/PVA electrospun fibers It was worth to note that the thermal decomposition can be categorized into three different regions From room temperature to 200 C, a 10% weight loss was observed; it involved the removal of water The GA/PVA electrospun fibers easily adsorbed moisture It commonly has a strong affinity for water adsorption and, therefore, may be easily hydrated, resulting in a molecule with a rather disordered structure [29] Between 200 and 500 C, weight loss was due to the decomposition of the polyvinyl alcohol The weight loss of the sample was due to pyrolysis; the electrospun fibers decomposed, producing CO and CO2 in this step On the other hand, in the presence of the gallic acid, the change of weight loss was shifted to a slightly higher temperature A possible reason for this may be the higher thermal stability provided by the phenolic content due to the aromatic group Above 500 C, the change in the weight loss of the electrospun fibers was terminated The product was changed to char and residual Fig exhibits the DSC curve of GA/PVA electrospun fibers The glass transition temperature was estimated to be 50 C With the existence of the gallic acid, the glass transition temperature was slightly shifted to higher temperature After that, with the increment on temperature, the second sharp peak appearing nearby 190 C was concerned with an endothermic effect induced by melting of the poly vinyl alcohol [30] The endothermic peak was slightly shifted to lower temperature with the increasing of gallic acid due to the interaction between the carbonyl group and the amine group in the composite fiber system (Fig 4) However, it was controversial that with the existence of the gallic acid, the temperature region of the endothermic peak should be shifted to higher temperature It was due to the fact that the gallic acid structure was involved in the phenolic compound, and it was subsequently difficult to decompose when the composite fibers was heated to high temperature [31] However, it was remarkable to note that with the existence of the gallic acid, the crystallinity of the composite fibers was decreased, resulting in the melting absorption peak becoming broad and shifting to lower temperature Next to this, the second endothermic peak for the composite fibers was found to appeared at ~320 C Fig Thermal decomposition characteristics of the gallic acid-loaded electrospun poly vinyl alcohols 178 P Chuysinuan et al / Journal of Science: Advanced Materials and Devices (2018) 175e180 3.1 Release profile of gallic acid from GA/PVA electrospun fibers Fig DSC thermoscans of the gallic acid-loaded electrospun poly vinyl alcohols Morphological properties of the GA/PVA electrospun fibers were investigated by SEM With the magnification of 20000Â, the diameter of composite fibers was estimated to be 1e5 micron Highly uniform and smooth composite fibers were prepared without the occurrence of bead defects It was remarkable to note that for the GA/PVA electrospun fibers, some bulges could be detected It was believed to be the phenolic group, showing the shape of spindle and sphere On the other hand, with the increment of gallic acid, the diameter of the electrospun fibers increased While the supply voltage and electric field were constant, the process became more difficult The diameter of the electrospun fibers was therefore increased This discussion was strongly associated with the previous article reported by Yang et al [32] The release of gallic acid from the GA/PVA electrospun fibers into phosphate buffer solution pH 7.4 was measured by using UVVis spectrophotometer, and the results concerning the concentration of accumulative release versus the submersion time are shown in Fig At first 60 after submersion, the burst release of the sample was observed The gallic acid released was gradual (60e2880 min), with a lower release rate It was attributed to the release of the encapsulated gallic acid, which was fully released after 2880 The result showed that the release of the gallic acid from the GA/PVA electrospun fibers is related to the concentration of gallic acid When the gallic acid content was increased, more gallic acid percent was released The maximum gallic acid release was observed for the GA/PVA electrospun fibers containing 2.5, 5, and 7.5% gallic acid, which were determined to be 9.75 ± 2.2%, 10.44 ± 3.3%, and 10.87 ± 0.36%, respectively 3.2 Total phenolic content and antioxidant activities 3.2.1 Total phenolic content Total phenolic contents of the GA/PVA electrospun fibers were displayed in Table The 2.5%, 5%, and 7.5% GA/PVA electrospun fibers had the average total phenolic content of 35.01 ± 7.55, 42.23 ± 9.06, and 44.42 ± 2.84 mg GAE/g extract, respectively 3.2.2 DPPH, radical scavenging assay The antioxidant capacity was analyzed using DPPH, scavenging assay (Table1), which showed an increase with the amount of gallic acid The highest DPPH, scavenging activity found in the 7.5% GA/ PVA electrospun fiber was 48.58 ± 0.19%, followed by those of the Fig SEM micrographs of the gallic acid-loaded electrospun poly vinyl alcohols (a) neat PVA, (b) 2.5%wt of the gallic acid, (c) 5%wt of the gallic acid, and (d) 7.5%wt of the gallic acid P Chuysinuan et al / Journal of Science: Advanced Materials and Devices (2018) 175e180 179 Fig Cumulative release characteristics of the gallic acid-loaded electrospun poly vinyl alcohols Table Antioxidant properties of the gallic acid-loaded electrospun poly vinyl alcohols Sample Anti-oxidant activity DPPH assay (%) ABTS assay (%) FRAP assay (mg TE/g extract) Neat GA 2.5% GA 5% GA 7.5% 45.14 ± 5.42 47.98 ± 2.73 48.58 ± 0.19 34.42 ± 5.86 41.99 ± 4.57 95.67 ± 0.29 1.39 ± 0.43 2.41 ± 0.25 2.70 ± 0.43 2.5% and 5% GA/PVA electrospun fibers (45.24 ± 5.42% and 47.98 2.78%), respectively 3.2.3 ABTSỵ radical scavenging assay As shown in Table 1, the ABTSỵ values of GA/PVA electrospun fibers increased with increasing gallic acid concentration, and the ABTS ỵ radical scavenging activity ranged from 34.42 5.86% to 95.67 ± 0.29% 3.2.4 Ferric reducing antioxidant power (FRAP) assay Compared with the neat electrospun poly vinyl alcohol fibers, the values of FRAP of the GA/PVA electrospun fibers were higher than that of the control sample The 7.5% GA/PVA electrospun fibers showed the highest FRAP scavenging activity (2.70 ± 0.43 mg TE/g extract), followed by those of 2.5% and 5% g GA/PVA electrospun fibers (1.39 ± 0.43 and 2.41 ± 0.25 mg TE/g extract) The finding that the incorporation of gallic acid into a polymer matrix caused increase in the antioxidant activity was also reported by Rui et al [33] who showed that the gallic acid-grafted-chitosan films possessed enhanced antioxidant activities and the effect increased when increasing the concentration of gallic acid by using DPPH and ABTSỵ radical scavenging assay Total phenolic content (mg GAE/g extract) 35.01 ± 7.55 42.23 ± 9.06 44.42 ± 2.84 employed as a crosslinking agent The thermal, morphological, structural and surface properties of the gallic acid loaded electrospun poly vinyl alcohols were characterized With increasing the gallic acid content, the diameter of the poly vinyl alcohol increased The gallic acid loaded electrospun poly vinyl alcohol based fibers exhibited excellent antioxidant properties The release profile of the chitosan-based composite investigated in phosphate buffer solution was found to follow the pseudo-Fickian model for 48 h The gallic acid loaded electrospun poly vinyl alcohol based fibers also exhibited good properties for use in a drug delivery system, in the wound healing and cosmetics Acknowledgments The authors would like to acknowledge the financial support provided by Thammasat University We are grateful for the space and research facilities support by the Chulabhorn Research Institute We would like to thank Mr Nitirat Chimnoi for research facilities support and Ms Kittiporn Trisupphakant for assisting on characterization References Conclusion We investigated the physico-chemical properties of the gallic acid loaded electrospun poly vinyl alcohol based fibers TEOS was [1] M Kitsara, et al., Fibers for hearts: a critical review on electrospinning for cardiac tissue engineering, Acta Biomater 48 (2017) 20e40 [2] L.A Mercante, et al., Electrospinning-based 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vinyl alcohols 178 P Chuysinuan et al / Journal of Science: Advanced Materials and Devices (2018) 175e180 3.1 Release profile of gallic