Sodium alginate/poly(vinyl alcohol)/nano ZnO composite nanofibers for antibacterial wound dressings

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Abstract

Sodium alginate (SA)/poly (vinyl alcohol) (PVA) fibrous mats were prepared by electrospinning technique. ZnO nanoparticles of size ∼160 nm was synthesized and characterized by UV spectroscopy, dynamic light scattering (DLS), XRD and infrared spectroscopy (IR). SA/PVA electrospinning was further carried out with ZnO with different concentrations (0.5, 1, 2 and 5%) to get SA/PVA/ZnO composite nanofibers. The prepared composite nanofibers were characterized using FT-IR, XRD, TGA and SEM studies. Cytotoxicity studies performed to examine the cytocompatibility of bare and composite SA/PVA fibers indicate that those with 0.5 and 1% ZnO concentrations are less toxic where as those with higher concentrations of ZnO is toxic in nature. Cell adhesion potential of this mats were further proved by studying with L929 cells for different time intervals. Antibacterial activity of SA/PVA/ZnO mats were examined with two different bacteria strains; Staphylococcus aureus and Escherichia coli, and found that SA/PVA/ZnO mats shows antibacterial activity due to the presence of ZnO. Our results suggest that this could be an ideal biomaterial for wound dressing applications once the optimal concentration of ZnO which will give least toxicity while providing maximum antibacterial activity is identified.f

Introduction

In recent years, there has been a growing interest among the researchers to incorporate metal nanoparticles into polymer nanofibers so as to make antibacterial electrospun mats. The wound dressing application of the electrospun mats using nano silver, zinc oxide etc. are already been reported using various degradable and non-degradable polymers. Electrospinning, a simple and a low cost method for making the nanofibers with ultra-small diameters was first patented by Antonio Formhals in 1934 [1]. Due to their high specific surface area and porous structure, the electro spun nonwoven fabrics consisting of ultrafine fibers find wide applications as scaffolds for tissue engineering [2], [3], tissue repair substitutes, wound dressing materials [4], [5] and carriers for drug delivery [6].

Alginate, a biodegradable polymer is a negatively charged polysaccharide derived from brown sea weed. It gains negative charge from the carboxyl groups located on the ring structure of both the M and G monomers. Unlike chitosan, alginate is readily soluble in water. It is a linear polysaccharide copolymer that consists of two sterically different repeating units 1,4α-l guluronate and 1,4β-d mannuronate in varying proportions [7]. The unique properties of sodium alginate are its biological origin, non-toxicity, hydrophilicity, biocompatibility, biodegradability and low cost [8], [9] makes it suitable for many biomedical applications. Due to its good tissue compatibility, it has been widely used in the field of tissue engineering including regeneration of skin [10], cartilage [11], bone [12], [13] and liver [14], [15] and in the treatment of exuding wounds and in enhancing the healing process [16].

Alginates, like chitosan, have many potential uses in bulk form. Due to biocompatibility and protein release properties of alginate matrices, there has been extensive interest in drug delivery applications [17]. The pH sensitivity and the stability of alginate based beads have been developed for controlled drug delivery systems [18]. The rigid and fragile nature of the gelatinous alginates may also be unfavorable in processing into non-spherical forms such as films and filaments via the gel state. A method to overcome this drawback is to blend the polysaccharide with a compatible flexible vinyl polymer. Most of the natural polymers, even though they have biocompatibility and biodegradability; they have poor mechanical properties and processing difficulties when compared with the synthetic polymers. There are reports which substantiate the electro spinnability of alginate with synthetic polymers such as PVA and poly (ethylene oxide) (PEO) [19], [20], [21], [22].

In this work we have blended SA with PVA for making them into nanofibers. PVA is a poly hydroxy polymer, which is water-soluble and has good fiber forming ability, biocompatibility, chemical resistance and biodegradability [23], [24]. Also there are reports related with the electrospinning of PVA from aqueous solutions [25]. In SA/PVA electrospinning, PVA interacts with SA through hydrogen bonds to form SA/PVA composite fibers. Also it is known that PVA can form gels with various solvents and co solvents. All these properties make PVA suitable for medical, cosmetic, food, pharmaceutical and packaging applications. In this work, we developed SA/PVA/ZnO nanofibrous mats for wound dressing applications.

Section snippets

Materials

Sodium alginate (SA) (medium molecular weight) was purchased from Sigma Aldrich. Poly (vinyl alcohol) (PVA) (medium molecular weight) was purchased from Qualigens. Methanol, gluteraldehyde, sodium hydroxide and zinc acetate were obtained from Merk. Syringes and needles were purchased from BD Sciences Ltd., Spain. All the chemicals were used as received.

Preparation and characterization of zinc oxide nanoparticles

Zinc oxide (ZnO) nanoparticles were prepared by sol–gel method [26]. Briefly, 0.1 M sodium hydroxide in methanol was added dropwise to 0.1 M zinc

Preparation and characterization of ZnO nanoparticles

ZnO nanoparticles show a characteristic sharp absorption peak around 360 nm in the UV spectrum at an intensity of 2, which is adequate to confirm the formation of particles (Fig. 1A). The average particle size obtained from DLS was 164 ± 2 nm (Fig. 1B). The typical XRD pattern of ZnO nanoparticles is shown in Fig. 1C. The characteristic peaks well matches with the pattern bulk ZnO [26]. The sharp peaks at diffraction angles (2θ) of 33.2° and 36.3° corresponds to the diffraction planes 1 0 0 and 1 0 1

Conclusions

SA/PVA nanofibrous mats were prepared by electrospinning technique. ZnO nanoparticles with average diameter 160 nm was synthesized and characterized. SA/PVA/ZnO nanofibrous mats with 0.5, 1, 2 and 5% ZnO concentrations were also prepared and found that fiber diameter is slightly increasing due to the addition of particles. Thermal studies show that ZnO incorporation altered the thermal stability of virgin SA/PVA fibers to a higher value due to the formation of composite fibers. Antibacterial

Acknowledgements

The authors are thankful to the Nanomission, Department of Science and Technology (DST), Govt. of India and Fast Track Scheme for Young Investigators (Ref. No. SR/FT/CS-005/2008) for the financial support. The author Shalumon K.T. is grateful to Council of Scientific and Industrial Research (CSIR) for awarding Senior Research Fellowship (SRF). We are also grateful to Mr. Sajin P. Ravi, Ms. Soumya and Ms. Chandini for their assistance in characterization and cellular studies.

References (29)

  • S. Agarwal et al.

    Polymer

    (2008)
  • R. Jayakumar et al.

    Carbohyd. Polym.

    (2010)
  • L. Sennerby et al.

    Biomaterials

    (1987)
  • Z. Li et al.

    Biomaterials

    (2005)
  • J.W. Lu et al.

    Polymer

    (2006)
  • W.C. Lin et al.

    Colloids Surf. B: Biointerfaces

    (2006)
  • K.T. Shalumon et al.

    Carbohyd. Polym.

    (2009)
  • N. Bhattarai et al.

    Biomaterials

    (2005)
  • K.T. Shalumon et al.

    Carbohyd. Polym.

    (2010)
  • A. Formhals, 500283...
  • N. Bolgen et al.

    J. Biomed. Mater Res. Part B: Appl. Biomater.

    (2007)
  • R. Lakshman et al.

    J. Macromol. Sci. Pure Appl. Chem.

    (2010)
  • F. Ignatious et al.

    Pharm. Res.

    (2010)
  • N. Bhattarai et al.

    Nanotechnology

    (2007)
  • Cited by (0)

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