Co-spinning of Silver Nanoparticles with Nisin Increases the Antimicrobial Spectrum of PDLLA: PEO Nanofibers

Silver nanoparticles (AgNPs), synthesized using N,N-dimethylformamide (DMF), were electrospun with nisin in a 50:50 blend of 24 % (w/v) poly(d,l-lactide) (PDLLA) and poly(ethylene oxide) (PEO). Addition of AgNPs decreased the average diameter of the nanofibers [silver nanofibers (SF)] from 588 +/- A 191 to 281 +/- A 64 nm, or to 288 +/- A 63 nm when nisin was co-spun with AgNPs. Nanofibers containing AgNO3 (SF) had a beads-on-string structure, whereas nanofibers with AgNPs and nisin [silver plus nisin nanofibers (SNF)], nanofibers with only nisin [nisin nanofibers (NF)], and nanofibers without AgNPs and nisin [control nanofibers] had a uniform structure. The irregular topography was confirmed by atomic force microscopy. No interactions occurred between silver, nisin, PDLLA, and PEO, as confirmed with Fourier transform infrared spectroscopy. Most of the AgNPs (18 +/- A 2.8 ppm) and nisin (78.1 +/- A 1.2 A mu g/ml) were released within the first 2 h. SF and SNF inhibited the growth of gram-positive and gram-negative bacteria, whereas NF failed to inhibit gram-negative bacteria. A wound dressing with broad-spectrum antimicrobial activity may be developed by the incorporation of nanofibers containing a combination of AgNPs and nisin.