Electrospun nanofibers embedded with silver nanoparticles: preparation, characterization and antibacterial activity

Introduction. The electrospinning of biodegradable polymers and its potential applications have recently been the subject of a large number of studies in the field of biomaterials. The high surface area and porosity of the obtained nanofibers make them particularly attractive to a large number of medical applications, i.e.: filtration, tissue engineering, implants, wound dressing and drug delivery. In parallel, a considerable interest on the use of silver nanoparticles use, due to their known antibacterial activity, has developed. The purpose of this work was to evaluate the antibacterial activity of both nano polymeric fibers of poly lactic acid (PLA) and PLA containing nanoparticles of silver (Ag) produced by an alternative, one-step, electrospinning method. Materials and methods. The nanofibers (PLA and PLA + Ag) obtained by an electrospinning technique have been characterized morphologically by SEM and TEM. Both nanofibers were subsequently tested to evaluate their antibacterial activity against two reference bacterial strains: Staphylococcus epidermidis (ATCC 35984) and Escherichia coli (ATCC 25922). The nanofibers PLA and PLA+Ag were sterilized by UV, placed in the presence of a bacterial inoculum of 107 CFU/ml and incubated for 15, 24 and 48 hours at 37°C. Controls without nanofibers were also performed. After the incubation time, for each sample the number of CFU/ml was quantified by TSA plate count. All the experiments were performed in triplicate. The results were analyzed by descriptive statistics and tested by unpaired T-test (p<0.05). Results. The resultant fibers exhibited uniform morphology with silver nanoparticles distributed throughout the fiber. Our results demonstrated that no antibacterial activity was detected for the PLA nanofibers. Further on, a significant (p<0.01) activity against both S. epidermidis and E. coli was observed to be more pronounced for the PLA embedded with Ag, during the course of the experiments. Discussion and conclusions. Although there has been only a partial Ag release from nanofibers during the experiment times, a significant antimicrobial activity, exerted by PLA+Ag against two common types of pathogens, was detected and attributed to the presence of Ag nanoparticles. Further studies on the biocompatibility, cytocompatibility, and antimicrobial properties of the obtained nanofibers will pave the way for potential applications in medical areas such as in the field of wound dressing.