Electrospun characteristics of gallic acid loaded poly vinyl alcohol fibers release characteristics and antioxidant properties

Original ArticleElectrospun characteristics of gallic acid-loaded poly vinyl alcohol ﬁbers: Release characteristics and antioxidant properties P.. The electrospunﬁbers showed high antiox

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Original Article

Electrospun characteristics of gallic acid-loaded poly vinyl alcohol

ﬁbers: Release characteristics and antioxidant properties

P Chuysinuana, T Thanyacharoenb, S Techasakula,**, S Ummartyotinb,*

a Laboratory of Organic Synthesis, Chulabhorn Research Institute, Bangkok, Thailand

b Materials and Textile Technology, Faculty of Science and Technology, Thammasat University, Patumtani, Thailand

a r t i c l e i n f o

Article history:

Received 2 March 2018

Received in revised form

16 April 2018

Accepted 20 April 2018

Available online 27 April 2018

Keywords:

Gallic acid

Poly vinyl alcohol

Electrospun

Antioxidant

a b s t r a c t

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 alcoholfiber The resulting gallic acid loaded electrospunfiber based hydrogel presented a thermal resistance up to 200C 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 electrospunfibers increased The release profile of the electrospun fibers was investigated based on a diffusion method The electrospunfibers showed high antioxidant activities, which were monitored using DPPH, radical scavenging, ABTS,þradical 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/)

1 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

in-terest in textile technology, tissue engineering, and would dressing,

as well as a drug delivery system Electrospinning was therefore

referred to as aﬁber production technique It employed an electric

force to draw charges threads of polymer solution and polymer

melts up to the nano-scaleﬁbers[1,2] Utilization of the

electro-spinning technique has therefore captured the interest in

nano-scaleﬁber formation From a fundamental point of view,

electro-spinning was regarded as a well-known and versatile technique to

fabricateﬁber materials This technique has also gained many

in-terests for making compositeﬁbers, porous structure ﬁbers,

poly-mer ﬁbers and so on This technique provided signiﬁcant

advantages such as high surface area to volume ratio, ease ofﬁber

functionalization, ease of material combination, ease of ﬁber deposition onto other substrateﬁbers, 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 ma-terials 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 tech-nique, 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

* 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.

Contents lists available atScienceDirect Journal of Science: Advanced Materials and Devices

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d

https://doi.org/10.1016/j.jsamd.2018.04.005

Journal of Science: Advanced Materials and Devices 3 (2018) 175e180

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proposed In 2013, Bosworth et al.[17]reported on state of the art of

the composite prepared from an electrospunﬁbers 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

electrospunﬁbers 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

char-acteristics were then tested and reported

2 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 matrixﬁbers, the 10% w/v of

polyvinyl alcohol (PVA) was dissolved in DI water and heated at

80C 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 4 h at room temperature to achieve a homogeneous

solution The electrospinning system, equipped with a high voltage

power supply unit under aﬁxed 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 electrospunﬁbers were immersed in water for 3 h

and then the solution was reacted with 2 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 2 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 electrospunﬁbers were

monitored using DPPH radical scavenging, ABTSþ radical

scav-enging 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 min 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 activityð%Þ ¼

ðAblank AsampleÞ Ablank

100

where Ablankand Asample are the absorbance values of the blank solution (0.3 mM DPPH solution) and the sample solution, respectively

b ABTS,þradical scavenging assay

The ABTS,þ radical cation scavenging capacity of the GA/PVA

electrospun ﬁbers was determined according to the procedure described by Finley et al.[23] The ABTS,þradical cation solution was obtained from the reaction of 2.6 mM potassium persulfate in water with 7.4 mM ABTS,þin 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 electrospunﬁbers immersing in water, were reacted with ABTS,þsolution and

incu-bated for 2 h ABTS,þradical scavenging capacity was calculated using the following formula:

Scavenging activityð%Þ ¼

ðAblank AsampleÞ Ablank

100

where Ablankis the absorbance of the ABTS,þradical without the

antioxidant materials and Asampleis the absorbance of the ABTS,þ radical in the presence of the antioxidant materials after 2 h

c Ferric reducing antioxidant power (FRAP) The antioxidant capacity of 2.5, 5, and 7.5% GA/PVA electro-spunﬁbers 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 FeCl3in 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 (Fe3þ TPTZ) complex was reduced to ferrous (Fe2þ) 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 electrospunﬁbers 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 37C ranging between 0 and 2880 min The medium

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solution was removed, the fresh medium with equal amount was

replaced, and the amount of GA release from the GA/PVA

electro-spunﬁbers was measured using a microplate reader by measuring

the absorbance at 260 nm

2.3 Instruments

The surface morphology was determined using scanning

elec-tron microscope (JEOL JSM-6400) The samples were cut into

cir-cular shape with an average diameter of 1.5 cm Specimens were

coated with a thin gold layer using a sputter Theﬁber diameters

were measured using a SemAphore 4.0 software at 20000

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 cm1at

room temperature and attenuated total reﬂectance (ATR) mode at a

resolution of 4 cm1

Thermal stability was evaluated by thermo gravimetric analysis

(209 F3 Tarsus, NETZSCH) The samples were heated from room

temperature to 700C with a heating rate of 10C/min under

ni-trogen atmosphere

Thermal behavior was investigated using a differential scanning

calorimeter (204 F1 Pheonix) under nitrogen atmosphere The

samples were heated from room temperature to 300C at a heating

rate of 10C/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 polytetra

ﬂuoro-ethylene (PTFE) reference cell

3 Results and discussion

Electrospun characteristics of the GA/PVA electrospun ﬁbers

were successfully conducted.Fig 1exhibits the FTIR spectra of the

GA/PVA electrospun ﬁbers Note that at a wavenumber of

3400 cm1, 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 cm1 It was slightly shifted to a higher wavenumber when

the gallic acid was loaded into the electrospun ﬁbers It was

obviously observed that the characteristic peak at 1710 cm1was 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 cm1[28] Meanwhile, the characteristic peaks of the electrospunﬁbers from 500 to 1000 cm1did 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 2shows the thermal decomposition characteristic of the GA/PVA electro-spunfibers It was worth to note that the thermal decomposition can be categorized into three different regions From room tem-perature to 200C, a 10% weight loss was observed; it involved the removal of water The GA/PVA electrospunfibers 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 500C, 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 CO2in 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 500C, the change in the weight loss of the electrospunﬁbers was terminated The product was changed to char and residual

Fig 3exhibits the DSC curve of GA/PVA electrospunﬁbers The glass transition temperature was estimated to be 50C With the existence of the gallic acid, the glass transition temperature was slightly shifted to higher temperature After that, with the incre-ment 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 compositeﬁber 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 fi-bers was heated to high temperature [31] However, it was remarkable to note that with the existence of the gallic acid, the crystallinity of the compositefibers was decreased, resulting in the melting absorption peak becoming broad and shifting to lower temperature Next to this, the second endothermic peak for the compositefibers was found to appeared at ~320C.

Fig 2 Thermal decomposition characteristics of the gallic acid-loaded electrospun

P Chuysinuan et al / Journal of Science: Advanced Materials and Devices 3 (2018) 175e180 177

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Morphological properties of the GA/PVA electrospunﬁbers were

investigated by SEM With the magniﬁcation of 20000, 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

asso-ciated with the previous article reported by Yang et al.[32]

3.1 Release profile of gallic acid from GA/PVA electrospun fibers The release of gallic acid from the GA/PVA electrospunfibers into phosphate buffer solution pH 7.4 was measured by using UV-Vis spectrophotometer, and the results concerning the concentra-tion of accumulative release versus the submersion time are shown

inFig 5 Atﬁrst 60 min 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 min The result showed that the release of the gallic acid from the GA/PVA electrospunﬁbers 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 electrospunﬁbers 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 electrospunﬁbers were displayed inTable 1 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 electrospunﬁber was 48.58 ± 0.19%, followed by those of the Fig 3 DSC thermoscans of the gallic acid-loaded electrospun poly vinyl alcohols.

Fig 4 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.

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2.5% and 5% GA/PVA electrospun ﬁbers (45.24 ± 5.42% and

47.98± 2.78%), respectively

3.2.3 ABTSþradical scavenging assay

As shown inTable 1, the ABTSþvalues of GA/PVA electrospun

ﬁbers increased with increasing gallic acid concentration, and the

ABTSþ 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 alcoholﬁbers,

the values of FRAP of the GA/PVA electrospunﬁbers were higher

than that of the control sample The 7.5% GA/PVA electrospunﬁbers

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)

Theﬁnding 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 ABTSþradical scavenging assay

4 Conclusion

We investigated the physico-chemical properties of the gallic

acid loaded electrospun poly vinyl alcohol basedﬁbers TEOS was

employed as a crosslinking agent The thermal, morphological, structural and surface properties of the gallic acid loaded electro-spun 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 basedfibers 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 basedfibers also exhibited good properties for use in a drug delivery system, in the wound healing and cosmetics

Acknowledgments The authors would like to acknowledge theﬁnancial support provided by Thammasat University We are grateful for the space and research facilities support by the Chulabhorn Research Insti-tute We would like to thank Mr Nitirat Chimnoi for research fa-cilities support and Ms Kittiporn Trisupphakant for assisting on characterization

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Fig 5 Cumulative release characteristics of the gallic acid-loaded electrospun poly vinyl alcohols.

Table 1

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P Chuysinuan et al / Journal of Science: Advanced Materials and Devices 3 (2018) 175e180 179

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