Surfactin-loaded polyvinyl alcohol (PVA) nanofibers alters adhesion of Listeria monocytogenes to polystyrene

Abstract

Surfactin-loaded polyvinyl alcohol (PVA) nanofibers were spun using gravity electrospinning. Scanning electron microscopy (SEM) images showed that nanofibers spun with surfactin are free from bead formation and uniform in diameter. The average nanofiber diameters were decreased (273±39nm, 259±39nm and 217±33nm) with increasing levels of surfactin (0.5, 1.0 and 1.5%, w/v) into PVA (10%, w/v). The 10% (w/v) PVA had average fiber diameter of 303±33nm. Atomic force microscopy (AFM) analysis showed that fibers spun with surfactin are not smooth as PVA fibers. The surface average roughness (S_a) estimated for surfactin loaded nanofibers (0.5%: 19.0nm, 1.0%: 20.4nm and 1.5%: 20.7nm) was higher as compared with PVA (10%:15.8nm). Scanning transmission electron microscopy (STEM) showed no matrix differences between PVA and surfactin-loaded PVA nanofibers. Fourier transform infrared (FTIR) microscopy revealed uniform distribution of surfactin in PVA. Based on differential scanning calorimetry (DSC) analyses, surfactin decreased the crystallinity of PVA during spinning. No antimicrobial activity was detected against methicillin-resistant Staphylococcus aureus (MRSA) strain Xen 30, Listeria monocytogenes EDGe, Escherichia coli Xen 14, and Pseudomonas aeruginosa PA01. However, the adhesion of L. monocytogenes to polystyrene in presence of surfactin-loaded nanofibers decreased significantly (OD₅₉₅: 0.012±0.001) as compared with control (OD₅₉₅: 0.022±0.002), suggesting that these nanofibers may be used in wound dressings or in the coating of prosthetic devices to prevent biofilm formation and secondary infections.

Keywords: Biofilms; Electrospinning; L. monocytogenes; Nanofibers; Polyvinyl alcohol; Surfactin.