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Preparation and Characterization of PVA/PVPNanofibers as Promising Materials for Wound DressingFaruk Gökmeşe a , İbrahim Uslu b & Arda Aytimur b c

a Department of Chemistry , Faculty of Arts and Sciences, Hitit University , Çorum , Turkeyb Department of Chemistry Education , Gazi Faculty of Education, Gazi University ,Teknikokullar , Ankara , Turkeyc Department of Advanced Technologies , Institute of Science and Technology, GaziUniversity , Teknikokullar , Ankara , TurkeyAccepted author version posted online: 27 Aug 2013.Published online: 05 Sep 2013.

To cite this article: Faruk Gökmeşe , İbrahim Uslu & Arda Aytimur (2013) Preparation and Characterization of PVA/PVPNanofibers as Promising Materials for Wound Dressing, Polymer-Plastics Technology and Engineering, 52:12, 1259-1265, DOI:10.1080/03602559.2013.814144

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Preparation and Characterization of PVA/PVP Nanofibers asPromising Materials for Wound Dressing

Faruk Gokmese1, Ibrahim Uslu2, and Arda Aytimur2,31Department of Chemistry, Faculty of Arts and Sciences, Hitit University, Corum, Turkey2Department of Chemistry Education, Gazi Faculty of Education, Gazi University,Teknikokullar, Ankara, Turkey3Department of Advanced Technologies, Institute of Science and Technology, Gazi University,Teknikokullar, Ankara, Turkey

The PVA/PVP, PVA/PVP with 5% and 10% chitosan andPVA/PVP-Iodine fibers were produced via electrospinning tech-nique. Their morphological and chemical characteristics were exam-ined with SEM, TGA, FT-IR, viscometer and four-point probeconductivity measurement apparatus. The addition of chitosanincreased the viscosity and the electrical conductivity of the poly-mer. The increase chitosan contents resulted in the diameters ofthe fibers smaller than expected. This was attributed to the increasein the viscosity of the solution and the electrical conductivity of theresulting fibers. The DSC results show that iodine was efficientlycross-linked with the polymer, forming an amorphous structure.

Keywords Chitosan; Electrospinning; Iodine; Nanofibers; PVA;PVP

INTRODUCTION

Poly (vinyl alcohol) (PVA) is a water-soluble polymersynthesized industrially by hydrolysis of poly (vinylacetate)[1]. It has been used in fiber and film products formany years. It has also widespread use as a paper coating,adhesives, colloid stabilizer and precursor polymer[1–5]. Inrecent years, much attention has been focused on the bio-medical applications of PVA hydrogels including contactlenses, artificial organs and drug delivery systems[1,6–20].

Poly (vinyl pyrrolidone) (PVP K-30) is an importantsynthetic polymer (Fig. 1). PVP K-30 has been used as afilm forming agent, viscosity enhancement agent, lubricatorand adhesive and it one of the most important ingredientsof hair sprays, mousse, gels and lotions, and solutions. Ithas found a widespread use in cosmetic market as skin careproducts, hair-drying reagents, shampoos, eye makeup,lipsticks, deodorants, sunscreen product and dentifricesdue to its low chemical toxicity and biocompatibility. It

is one of the most important materials used in detergents,paints, electronics, and biological engineering[21–29].

Chitosan is a semicrystalline polymer and is used in a widevariety of biomedical applications, such as drug deliverycarriers, surgical thread, bone healing and especially wounddressing materials[30]. It has found very wide applications inwound management in recent years. Chitosan could acceler-ate tensile strength of wounds by speeding the broblasticsynthesis of collagen in the first few days of wound heal-ing[31,32]. The electrospun PVP K-30 fibers were first synthe-sized by Bognitzki et al. in 2001[33]. Li et al. synthesizednanofibers of PVP K-30 and TiO2 (or SnO2) in 2003[34].

PVA and PVP K-30 hydrogels have been widelyexplored as water-soluble polymers for numerous biomedi-cal and pharmaceutical applications due to its nontoxic,noncarcinogenic and bioadhesive properties[35–37].

In this study PVA=PVP, PVA=PVP with 5% and 10%chitosan and PVA=PVP-Iodine fibers were produced withthe use of electrospinning technique as promising materialsfor wound dressing because of these polymers advantagesmentioned here. An electrospinning technique was usedin order to synthesize nanofiber because electrospinningis relatively cost-effective and an easy technique for nano-fiber fabrication.

EXPERIMENTAL

Materials

PVA (MW: 85,000–146,000 gmol�1, 98% hydrolyzed),chitosan (Mw 400,000 gmol�1) and acetic acid were obtainedfrom Merck (Darmstadt, Germany). All polymer solutionswere prepared using deionized water. Aqueous acetic acid(2% [v=v]) was used as a solvent because chitosan is only sol-uble in acetic acid. Granular polyvinyl pyrrolidone (PVP,K-30, pH, 10% in water 3.48 with K value 31.41) and poly-vinyl pyrrolidone iodine (PVP Iodine) were supplied byBASF (Ludwigshafen, Germany) and all the solutions wereprepared by the use of ultrapure distilled water as a solvent.

Address correspondence to Arda Aytimur, Departmentof Chemistry Education, Gazi Faculty of Education, GaziUniversity, Teknikokullar, Ankara, 06500, Turkey. E-mail:ardaaytimur@hotmail.com

Polymer-Plastics Technology and Engineering, 52: 1259–1265, 2013

Copyright # Taylor & Francis Group, LLC

ISSN: 0360-2559 print=1525-6111 online

DOI: 10.1080/03602559.2013.814144

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Sol Preparation

PVA hydrogel was prepared by fully dissolving 10.0 g ofpolymer powder without further purification in 100ml ofdeionized water, under magnetic stirring for 2 h, at tem-perature of 90�C. The 10% PVA solution was cooled toroom temperature. PVP hydrogel was prepared by com-plete dissolution of 6.0 g polymer powder without furtherpurification in 60ml ultrapure deionized water, under mag-netic stirring, at 60�C. PVA and PVP hybrid polymers wereproduced by mixing 30 g 10% PVA with 20 g 10% of PVPaqueous solutions for an hour at room temperature.

Then 5% and 10% chitosan were dissolved in aqueousacetic acid (2% [v=v]) by stirring overnight at room tem-perature. The PVA=PVP with 5% and 10% chitosan solu-tions were prepared by mixing these chitosan solutions indropwise manner in 50ml PVA=PVP aqueous hybrid poly-mer for two hours. PVA=PVP iodine hybrid polymer wasalso prepared in the same way as the PVP=PVA solution.The solutions were kept at room temperature for 24 h toremove air bubbles.

Electrospinning of Polymer Solution

Polymeric nanofibers can easily be prepared by an elec-trospinning process. Electrospinning uses a high electricfield to draw a polymer solution from the tip of a capillarytowards a collector. The applied voltage causes a jet of thesolution to be drawn toward a grounded collector. The finejets form nanosized polymeric fibers after they dry up, andthey are collected as a weblike mass.

Characterization and Measurement

The electrospinning equipment uses a variable high volt-age power supply from Gamma High Voltage Research(USA). The applied voltage can be varied from 0–40KV.The syringe needle was used as the electrode connected tothe power source. The collector was a 20� 40 cm2 alumi-num foil placed 15 cm horizontally from the tip of the nee-dle. The collector was connected to the power supply as anelectrode with opposite polarity. A metering syringe pumpfrom New Era Pump Systems Inc. (USA) was responsiblefor supplying polymer solution with a constant rate of0.5ml=h. Nanofibers were obtained by electrospinning

from PVA aqueous solutions at an electrical voltage of20 kV at room temperature under air atmosphere.

Fiber formation and morphology of the electrospunPVA=PVP, PVA=PVP with chitosan and PVA=PVP withiodine fibers were determined using a scanning electronmicroscope (SEM) Quanto 400 FEI MK-2 (Oregon, USA).

The fiber diameters were measured using the image pro-cessing software, ImageJ (Image Pro-Express, Version5.0.1.26, Media Cybernetics Inc.), which is a public domainJava image processing program.[38]

Fourier Transformation Infrared Spectra (FT-IR) withATR module were obtained using Thermo Nicolet 6700spectrophotometer (Thermo Scientific, Waltham, MA,USA). DSC studies of the nanofibers were carried out witha Shimadzu DSC-60 Differential Scanning Calorimeter(Shimadzu, Columbia, MD, USA) pH and conductivity ofthe solutions were measured by using a Wissenschaftlich-Technische-Werkstatten WTW and 315i=SET (Weilham,Germany) apparatus and the viscosity of the hybrid polymersolutions measured with an AND SV-10 viscometer.

Advancing and receding air=water contact angles weremeasured at room temperature by an image analyzing sys-tem, using the air bubble technique. The advancing anglewas obtained by placing a needle in deionized water andcreating a bubble on the sample surface (1–1.5mL) andcarefully expanding the bubble volume until the part ofthe bubble adjacent to the sample surface stopped chan-ging. Similarly, the receding angle was obtained when theair was sucked out of the bubble.

RESULTS AND DISCUSSION

Physical Properties of Solutions and Fibers

Table 1 lists the pH, solution viscosity, and solutionconductivity and fiber conductivity values. Since pH ofthe chitosan solution is lower than PVA and PVP K-30(PVP), the addition of chitosan 5% and 10% decreasedthe pH of the solution to 4.08 and 3.90. PVA=PVP is blend-ing a considerable increase in their viscosity because of thehydrogen bonding in the blended hybrid polymer.

Viscosity of chitosan solution is very high and theaddition of chitosan caused the viscosity of the PVA=PVP solution to increase. On the other hand, conductivityof PVA=PVP solution and its fibers has shown a consider-able increase by the addition of the chitosan. Increase ofthe conductivity of the solution affected the diameter ofthe final fibers because the net charge density carriedby the jet in the electrospinning process is affected by theconductivity of the solution. The higher net charge densityincreased the electrical force exerted on the jet and led todecreased fiber diameter.

DSC Analysis of Chitosan/PVA Nanofibers

Differential Scanning Calorimetry (DSC) measurementswere carried by using nitrogen as the carrier gas. The

FIG. 1. Chemical structure of poly (vinyl pyrrolidone).

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temperature was raised from room temperature to 200�Cthen cooled to room temperature, and the sample washeated again to 500�C at a rate of 10�C=min.

The DSC thermograms of PVA=PVP and PVA=PVPwith iodine fibers show the thermal properties of the twomain polymers. The DSC of PVA=PVP without chitosanfibers showed a melting endotherma at about 214�C and291�C and decomposition peaks at 430�C. As seen fromFig. 2, there are no sharp melting peaks when iodine addedto PVA=PVP blend polymer. It shows that iodine was effi-ciently cross-linked with the polymer forming an amorph-ous structure.

Figure 3 shows the DSC profiles measured for the PVAnanofibers. All the nanofibers have an endothermic peakaround 200–225�C, corresponding to the melting of PVA(Tm).

The Tm values were listed in Table 2. Other endothermicpeaks are around 291�C and 430�C. As seen from Fig. 3 allthese three peaks decrease considerably. For example thereare almost no melting peaks at about 212�C when 10%

chitosan solution added to PVA¼PVP blend polymersolution. Fig. 3 shows that chitosan was efficiently cross-linked with the polymer and an amorphous structurewas formed. In a summary, DSC analysis shows that whenchitosan is added to the polymer, it increases the cross-linking structure of PVA=PVP polymer.

FT-IR Analysis

Figure 4 shows the FT-IR spectrum of pure PVA 10%polymer solution and electrospun fiber. It clearly revealsthe major peaks associated with poly (vinyl alcohol). Forinstance, there are C–H broad alkyl stretching bands(2850–3000 cm�1) and typical strong hydroxyl bands forfree alcohol (nonbonded –OH stretching band at 3600–3650 cm�1), and hydrogen bonded bands (3200–3570 cm�1)for PVA 10% polymer solution. These results are similarto the results of the article by Uslu et al. in 2012[20]. AsUslu et al. mentioned, intramolecular and intermolecularhydrogen bonding are expected to occur among PVA

FIG. 2. DSC analysis of PVA=PVP-Iodine and PVA=PVP fiber.

FIG. 3. DSC thermogramic results of PVA=PVP fiber with no chitosan,

5% and 10% chitosan.

TABLE 1Physical properties of solutions and fibers

Solution pHSolution viscosity

(mPa � s)Solution conductivity

(mS � cm�1)Fiber conductivity�

10�6 (mS � cm�1)

PVA 5.92 1.11 959 –PVP 3.58 6.06 226 –Chitosan 3.37 310 2.80 –PVA=PVP blend soln. 5.23 261 673 7.09PVA=PVP with 5% chitosan 4.08 284 760 8.6PVA=PVP with 10% chitosan 3.90 298 863 14.9PVA=PVP with iodine 2.56 242 2.2 3.6

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chains due to high hydrophilic forces. These peaks areabsent for the PVA electrospun fibers as expected.

The absorption peak at 1096 cm�1 (C–O, 1090–1150 cm�1) is very sharp for the electrospun fiber. This isa carboxyl stretching band (C–O) and attributed to thecrystallinity of the PVA, which is used for the assessmentof poly (vinyl alcohol) structure.

Figure 5 is the FT-IR spectra of the PVA=PVPhydrogels obtained within the range between 4000 and400 cm�1. The absorption peaks at 1417 cm�1 (CH2 bend-ing) and 858 cm�1 (CH2 rocking) characteristic to PVAappear in all spectra. But the peak heights are different.The peak at 1270 cm�1 is due to the C-H vibration. The

absorption peak of the chitosan is located at 1657 cm�1,which is the characteristic peak of chitosan and reportedas amide I[39]. The broad peak at 1096 cm�1 indicates theC-O stretching vibration. The absorption peak of thePVP K-30 and chitosan C¼O group is located at1657 cm�1 and are present in all spectra of PVA=PVPhybrid polymers. However the peak height is graduallydecreased as the iodine is added, and the smallest peakappears for PVA=PVP with iodine.

Contact Angle Measurement

In Fig. 6 water drops on the PVA=PVP and PVA=PVP5% chitosan fiber surfaces are viewed to determine thecontact angles of the surfaces. The measured average con-tact inner and outer angles of the PVA=PVP fiber are 38.3�

and 141.6�. The average inner and outer contact angles forthe PVA=PVP 5% chitosan fibers are 46.2� and 133.8�.PVA=PVP was determined as the higher hydrophilic mate-rial than PVA=PVP 5% chitosan fiber according to thesecontact angle values.

SEM Analysis

The morphology of the PVA=PVP, PVA=PVP with 5%chitosan and PVA=PVP-Iodine fibers produced were exam-ined using SEM micrographs. Figure 7(a) shows the SEMimages of PVA=PVP fibers. There seen elongated andstraight electrospun nanofibers with relatively homoge-neous diameters ranging from 150 to 350 nm. The averagediameter of these nanofibers was measured as 247 nm.Figure 7(b) is the image of PVA=PVP with 5% chitosan.Fiber diameters range from 100 to 250 nm. Measured aver-age diameter is 168 nm for these nanofibers. Figure 7(c) isthe image of PVA=PVP-Iodine fibers with diameters ran-ging from 100 to 500 nm. The average diameter of PVA=PVP-Iodine nanofibers measured greater than the othersas 298 nm. Fiber diameter distributions could be seen fromFig. 8.

Addition of chitosan increased the viscosity of the poly-mer. The increase in chitosan contents resulted in the curlyand wavy fiber structures. This was attributed to theincrease in the viscosity of the solution and the electrical

FIG. 5. FT-IR spectrum of PVA=PVP and PVA=PVP-iodine.

FIG. 6. Water drops on: (a) the PVA=PVP fiber surface, and (b) the

PVA=PVP 5% chitosan fiber surface. (Color figure available online.)

FIG. 4. FT-IR spectrum of pure 10% PVA polymer solution and electro-

spun fiber.

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conductivity of the resulting fibers, which caused thediameters of the fibers being smaller than expected. PVA=PVP with iodine hybrid polymer showed higher tendencyto bead formation because of considerable lower conduc-tivity of the polymer as mentioned in the text.

CONCLUSIONS

The addition of chitosan increased the viscosity and theelectrical conductivity of the polymer. The resulting fiberswere curly and wavy in nature of the polymer. The increaseof chitosan contents resulted such that the diameters of thefibers were smaller than expected. This was attributed tothe increase in the viscosity of the solution and the electri-cal conductivity of the resulting fibers. The FT-IR spectrathe revealed that the absorption peak of C¼O group islocated at 1657 cm�1 gets gradually smaller as the iodineis added. The DSC results show that that iodine wasefficiently cross-linked with the polymer forming an amor-phous structure.

PVA=PVP with iodine hybrid polymer showed highertendency to bead formation because of the considerable

FIG. 8. Fiber diameter distributions of: (a) PVA=PVP fiber, (b) PVA=PVA with 5% chitosan fiber, and (c) PVA=PVP with iodine fiber.

FIG. 7. SEM picture of: (a) PVA=PVP fiber, (b) PVA=PVA with 5%

chitosan fiber, and (c) PVA=PVP with iodine fiber.

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lower conductivity of the polymer. The iodine and chitosancontaining PVA=PVP hybrid polymers were successfullysynthesized. They have an important potential for use aswound dressing material. The future studies will includeincreasing the moisture regain values of the polymers bygrafting acrylic acid on them with the use of plasma-enhanced vapor deposition, since it is a well-known factthat wounds heal quicker in moist media. The resultingpolymers will also be grafted with various antibiotics withEDTA in order to increase their wound-healing capacity.

ACKNOWLEDGMENTS

The present work is supported financially by theScientific and Technological Research Council of Turkey(TUBITAK) Project by Contract 106T630.

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