Antibacterial Ag containing core-shell polyvinyl alcohol-poly (lactic acid) nanofibers for biomedical applications

Core-shell-structured polyvinyl alcohol (PVA)-poly (lactic acid) (PLA) nanofibers combining the hydrophilic trait of PVA and the biocompatibility of PLA were produced using coaxial electrospinning. This allowed the incorporation of AgNO₃ in the PVA core of the distinct fibers as shown through transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) showed relatively uniform and bead-free fibers with smooth surfaces. Ag-containing fibers show significantly decreased diameters compared with Ag-free samples as a result of the increased conductivity of the spinning solutions with increasing amounts of AgNO₃. In a postsynthetic treatment, the AgNO₃ was reduced forming silver nanoparticles (Ag NPs). Ag NPs of 45 to 90 nm size were located in the PVA core but also on the surface of the core-shell fibers and as individual, agglomerated, and polymer-coated particles of 100-200 nm. Powder X-ray diffraction (PXRD), energy dispersive X-ray spectroscopy (EDX), and UV-vis absorption spectroscopy confirmed the increasing amounts of Ag in the core-shell fibers when using increasing amounts of AgNO₃ in the spinning solutions. The antibacterial activity of the nanofiber mats against two prokaryotes Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) increased with increasing amounts of Ag, as expected and produces inhibition zones of 1 to 2 mm.