Evaluate the effect of graphitic carbon nitride nanosheets decorated with copper nanoparticles on biofilm and icaA gene expression in Staphylococcus aureus isolated from clinical samples

The emergence, spread, and persistence of multidrug-resistant (MDR) bacteria have become a public health threat. Therefore, it is urgent to investigate novel antimicrobial materials without antibacterial resistance. In this regard, Copper/graphitic carbon nitride nanocomposites (Cu/g-C3N4 NCs) with different loading amounts of Cu nanoparticles (NPs) have been successfully prepared via the co-precipitation-sonication approach. The purity of the nanostructures was verified by the X-ray diffraction (XRD) pattern. The antibacterial activity of Cu/g-C3N4 NCs versus tested bacteria were determined by the microdilution technique. Inhibition of biofilm formation was also evaluated using the microtiter plate method. In addition, the ability of Cu/g-C3N4 NCs to the expression level of the icaA gene was assessed by the Real-Time PCR technique. Our results showed that the doping of graphitic carbon nitride with Cu-NPs can improve the antibacterial activity of g-C3N4. So, sample 4 (Cu:g-C3N4 1;1), with higher Cu content, had the highest antibacterial activity toward tested bacteria. The result also showed that sample 4 recorded the largest inhibition zone diameters against tested bacteria, including Staphylococcus aureus (29 mm) and Pseudomonas aeruginosa (16 mm). In addition, Cu/g-C3N4 NCs exhibited a 65% reduction in biofilm formation for Staphylococcus aureus. Moreover, icaA gene was down-regulated after treatment with Cu/g-C3N4 NCs. In conclusion, our study showed that extract Cu/g-C3N4 NCs can use as a promising anti-biofilm agent against biofilm–producing bacteria.