Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

Abstract

Herein, novel hybrid nanomaterials were developed for wound dressing applications with antimicrobial properties. Electrospinning was used to fabricate a double layer nanocomposite nanofibrous mat consisting of an upper layer of poly(vinyl alcohol) and chitosan loaded with silver nanoparticles (AgNPs) and a lower layer of polyethylene oxide (PEO) or polyvinylpyrrolidone (PVP) nanofibers loaded with chlorhexidine (as an antiseptic). The top layer containing AgNPs, whose purpose was to protect the wound site against environmental germ invasion, was prepared by reducing silver nitrate to its nanoparticulate form through interaction with chitosan. The lower layer, which would be in direct contact with the injured site, contained the antibiotic drug needed to avoid wound infections which would otherwise interfere with the healing process. Initially, the upper layer was electrospun, followed sequentially by electrospinning the second layer, creating a bilayer nanofibrous mat. The morphology of the nanofibrous mats was studied by scanning electron microscopy and transmission electron microscopy, showing successful nanofiber production. X-ray diffraction confirmed the reduction of silver nitrate to AgNPs. Fourier transform infrared spectroscopy showed a successful incorporation of the material used in the produced nanofibrous mats. Thermal studies carried out by thermogravimetric analysis indicated that the PVP-drug-loaded layer had the highest thermal stability in comparison to other fabricated nanofibrous mats. Antimicrobial activities of the as-synthesized nanofibrous mats against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were determined using disk diffusion method. The results indicated that the PEO-drug-loaded mat had the highest antibacterial activity, warranting further attention for numerous wound-healing applications.

Keywords: activity; antimicrobial; biomedical; electrospinning; nanofibers; nanomaterials; wound dressing.

Figure 1

SEM image of fabricated electrospun mat. Notes: SEM image at 20,000× of electrospun nanofibers of PVA/chitosan/AgNPs blends of 12 wt%/0.6 wt%/0.9 wt%, respectively, using the following electrospinning conditions of 10 cm, 18 kV, and 0.3 mL/h. The EDS was collected on the PVA/chitosan/AgNPs. Abbreviations: SEM, scanning electron microscopy; PVA, poly(vinyl alcohol); AgNPs, silver nanoparticles; EDS, energy dispersive spectrum; wt, weight; HV, high voltage; Mag, magnification; WD, working distance.

Figure 2

SEM image of fabricated electrospun mat. Note: SEM image at 20,000× of electrospun nanofibers of PVP 12% (wt/v) using the following electrospinning conditions of 10 cm, 18 kV, and 0.3 mL/h. Abbreviations: SEM, scanning electron microscopy; PVP, polyvinylpyrrolidone; v, volume; wt, weight; HV, high voltage; Mag, magnification; WD, working distance.

Figure 3

SEM image of fabricated electrospun mat. Note: SEM image at 1,000× of electrospun nanofibers of PEO 8% (wt/v) using the following electrospinning conditions of 10 cm, 18 kV, and 0.3 mL/h. Abbreviations: SEM, scanning electron microscopy; PEO, polyethylene oxide; v, volume; wt, weight; HV, high voltage; Mag, magnification; WD, working distance.

Figure 4

TEM image showing AgNPs on a nanofiber. Abbreviations: TEM, transmission electron microscopy; AgNPs, silver nanoparticles.

Figure 5

Comparative result of FT-IR spectra for all fabricated samples. Notes: FT-IR shown is for (A) PVA, (B) chitosan, (C) PVA/chitosan, (D) PVA/chitosan/AgNPs, (E) PVA/chitosan/AgNPs/PVP/chlorhexidine, and (F) PVA/chitosan/AgNPs/PEO/chlorhexidine. Abbreviations: FT-IR, Fourier transform infrared spectroscopy; PVA, poly(vinyl alcohol); AgNPs, silver nanoparticles; PVP, polyvinylpyrrolidone; PEO, polyethylene oxide.

Figure 6

Comparative result of TGA spectra for all samples. Notes: TGA shown is for PVA, chitosan, PVA/chitosan, PVA/chitosan/AgNPs, PVA/chitosan/AgNPs/PVP/chlorhexidine, and PVA/chitosan/AgNPs/PEO/chlorhexidine. Abbreviations: TGA, thermogravimetric analysis; PVA, poly(vinyl alcohol); AgNPs, silver nanoparticles; PVP, polyvinylpyrrolidone; PEO, polyethylene oxide.

Figure 7

XRD spectra for electrospun PVA/chitosan/AgNPs. Note: The four diffraction peaks are ascribed to corresponding reflection planes of FCC structure of Ag phase. Abbreviations: XRD, X-ray diffraction; PVA, poly(vinyl alcohol); AgNPs, silver nanoparticles; FCC, face-centered cubic; au, atomic unit; Ag, silver.

Figure 8

Antimicrobial susceptibility disk diffusion test. Notes: (1) PVA/chitosan (control), (2) PVA/chitosan/AgNPs, (3) PVP-drug loaded, and (4) PEO–drug loaded against (A) Staphylococcus aureus, (B) Escherichia coli, (C) Pseudomonas aeruginosa, and (D) Candid albicans. Abbreviations: PVA, poly(vinyl alcohol); AgNPs, silver nanoparticles; PVP, polyvinylpyrrolidone; PEO, polyethylene oxide.

Figure 9

Diameter of zones of inhibition for PVA/chitosan, PVA/chitosan/AgNPs, PVP/chlorhexidine, and PEO/chlorhexidine against S. aureus, P. aeruginosa, E. coli, and C. albicans. Abbreviations: PVA, poly(vinyl alcohol); AgNPs, silver nanoparticles; PVP, polyvinylpyrrolidone; PEO, polyethylene oxide; S. aureus, Staphylococcus aureus; P. aeruginosa, Pseudomonas aeruginosa; E. coli, Escherichia coli; C. albicans, Candida albicans.