Ciprofloxacin-Loaded Poly(N-isopropylacrylamide-co-acrylamide)/Polycaprolactone Nanofibers as Dual Thermo- and pH-Responsive Antibacterial Materials

Nanofibers are an attractive option in drug release, especially as antibacterial materials. However, there is no universal antibacterial material and little attention has been devoted to bacteria–nanofiber attachment. Poly(N-isopropylacrylamide-co-acrylamide) is particularly interesting due to its dual thermo- and pH-responsive nature. Here, we prepared stimuli-responsive antibacterial nanofibers by the blend electrospinning of polycaprolactone (PCL), various concentrations of PNIPAm-co-AAm and ciprofloxacin (CIP). The lower critical solution temperature (LCST) of PNIPAm-co-AAm was determined by refractometry in distilled water and buffer solutions at pH 4 and 7.4. Based on the results obtained, we performed release tests, which indicated that the amount of released CIP and its release kinetics were dependent on nanofiber composition. Moreover, the nanofibers showed enhanced release at temperatures below LCST and, in turn, this led to enhanced antibacterial activity, as demonstrated by disk diffusion tests on Staphylococcus epidermidis and Escherichia coli. In addition, both bacterial strains demonstrated much lower attachment to CIP-loaded PCL/PNIPAm-co-AAm compared with CIP-loaded PCL nanofibers. Furthermore, cytocompatibility tests, performed using primary human dermal fibroblasts, produced similar good cell spreading regardless of PNIPAm-co-AAm concentration. Collectively, our results show that the proposed nanofibers have considerable potential as materials, which promote wound healing and significantly decrease the probability of bacterial infection.