Selectively Enhanced Antimicrobial Activity by Combining Copper(II)-β-Cyclodextrin with Different Carbon Nanomaterials

Carbon nanomaterials are recognized for their biocompatible and potential antimicrobial agents. These materials are effectively employed in tandem with metal-based antimicrobials to augment antimicrobial efficacy. This study explores the synergistic interactions between sodium dodecyl sulfate (SDS) and copper(II)-β-cyclodextrin (Cu₂-β-CD) alongside various carbon nanomaterials, including hydrophilic graphene oxide (GO) and hydrophobic multi-walled carbon nanotubes (MWCNTs). These materials are strategically utilized to modulate microbial proliferation, thereby enhancing microbicidal and antibacterial outcomes. With 0.3% SDS presence and a carbon nanomaterial to Cu₂-β-CD mass ratio of 1:140, the minimum inhibitory concentration (MIC) of the Cu₂-β-CD@GO composite was reduced to 5.0 μg/mL and 2.5 μg/mL against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. Additionally, the MIC for the Cu₂-β-CD/MWCNTs mixture was established at 150 μg/mL against Candida albicans (C. albicans). The antimicrobial mechanism was elucidated through assays assessing cell membrane permeability and integrity, supplemented by scanning electron microscopy observation. Results demonstrated that the pronounced antimicrobial effects against diverse microbes resulted from the collaborative impact of Cu₂-β-CD, SDS, and GO or MWCNTs. Crucially, carbon nanomaterials played an essential role in selective sterilization, primarily due to the hydrophilic interaction between GO and bacterial strains as well as the hydrophobic interaction between MWCNTs and fungal pathogens.