The potential of copper-functionalized multi-walled carbon nanotubes against Staphylococcus aureus biofilms

Carbon nanotubes (CNTs) possess attractive properties for various applications. Recent research has shown that functionalizing or modifying CNTs with antimicrobial drugs, polymers, or metals can enhance their antimicrobial potential. Given the global challenge of biofilm formation, particularly on medical devices, this study explores the functionalization of multi-walled carbon nanotubes (MWCNTs) with copper (Cu-MWCNTs) and their efficacy against pre-established Staphylococcus aureus biofilms. Functionalized MWCNTs were characterized for copper content, metal and carbon leaching, morphology, elemental composition, textural properties, and zeta potential. S. aureus biofilms were formed for 48 h on polydimethylsiloxane (PDMS) surfaces and exposed to Cu-MWCNTs at their minimum inhibitory concentration (3 % w/v) for 6 h. Biofilms were analysed for changes in structure, and cell viability and culturability. The antimicrobial mechanisms and bacterial morphological changes were also examined. Material characterization confirmed the successful Cu functionalization of MWCNTs. After exposure to Cu-MWCNTs, the thickness and spatial distribution of S. aureus biofilms were altered. Additionally, biofilm cells showed a significant reduction in culturability by 1.30 and 0.56 Log compared to untreated or p-MWCNT-exposed controls, respectively, demonstrating a synergistic effect due to copper incorporation. Cu-MWCNTs compromised bacterial membrane integrity and reduced metabolic activity. These findings highlight the potential of Cu-MWCNTs as effective agents against pathogenic biofilms.