Characterization, antioxidant activity of banana peel carbon dots and their antibacterial mechanism against Staphylococcus aureus

AIMS: The carbon dots (CDs) used in this study are a type of carbon nanomaterial extracted from banana peels, which possess various biological activities and demonstrate significant advantages in the antimicrobial field. Staphylococcus aureus is one of the most common foodborne pathogenic bacteria, severely impacting human health and food safety, as well as causing substantial economic losses. This study investigates the properties of the CDs and their inhibition mechanism against S. aureus. METHODS AND RESULTS: The synthesized CDs were characterized using transmission electron microscopy, ultraviolet-visible spectroscopy, fluorescence spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The antioxidant activity and antimicrobial effect of CDs were explored through free radical scavenging and bacterial experiments. The cytocompatibility of CDs was determined by MTT assay. The results showed that spherical blue CDs of 6.4 ± 1.56 nm were synthesized. CDs showed a UV-visible absorption peak at 265 nm. CDs are rich in hydroxyl, carboxyl, and amino groups, demonstrating excellent water solubility, photostability, pH stability, and antioxidant properties. The findings showed that CDs disrupt the cell membrane structure of S. aureus, resulting in altered membrane permeability, leakage of cell contents, and accumulation of excessive ROS. The minimum inhibitory concentration was found to be 3.125 mg ml-1. Moreover, the CDs exhibited good cell compatibility. CONCLUSION: CDs are an ideal antioxidant and natural antibacterial agent that can inhibit S. aureus. The antioxidant effect of CDs is achieved through radical scavenging, and they exhibit good cytocompatibility. At the same time, CDs exhibits strong antifungal activity through mechanisms such as disrupting the cell membrane structure, altering membrane permeability, causing leakage of cellular contents, increasing malondialdehyde (MDA) levels, and accumulating intracellular ROS.