Innovative polycaprolactone/graphitic carbon nitride composite coatings: enhancing the antibacterial properties of nanoporous alumina membranes

Abstract

Despite the intensive need for antifouling coatings against bacterial contamination, issues remain. Herein, we present a novel approach to enhance the antifouling and antibacterial properties of nanoporous alumina membranes (ALNPMs) by coating them with polycaprolactone (PCL) and graphitic carbon nitride (g-C₃N₄). A porous PCL coating, functionalized with NHS/EDC, was deposited via a spin-coating technique onto the ALNPMs, incorporating g-C₃N₄ at ratios of 1 and 2 wt%. The coated membranes were characterized using SEM/EDX, TEM, FTIR/ATR, XRD, and contact angle measurements. The results revealed that the addition of g-C₃N₄ increased the hydrophilicity of the coated membranes. Contact angles reached 68.5° for 1 wt% and 78.9° for 2 wt% PCL containing g-C₃N₄ coatings compared to pure PCL at 96°. The antifouling properties of the coating were tested by determining the bovine serum albumin (BSA) adsorption and pH stability. At a higher content of g-C₃N₄ (2 wt%), the membrane showed lower BSA adsorption over 14 days (28%) alongside structural integrity. Antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) showed an increase in inhibition upon incorporation of g-C₃N₄. The membrane with 2 wt% g-C₃N₄ showed the highest effectiveness with inhibition zones of 36 and 30 mm for E. coli and S. aureus, respectively. Possible mechanisms for this improvement include increased hydrophilicity, physical destruction of bacterial membranes, and photocatalytic reactive oxygen species generation. Overall, PCL/g-C₃N₄ coatings significantly improve antifouling and antibacterial functionalities, which make them promising candidates for use in membrane technology for biomedical applications.