Antibacterial behavior and mechanism of nitrogen, silicon-doped amphiphilic carbon dots

Abstract

A new kind of amphiphilic carbon dots (CDs) was prepared with citric acid and silane coupling agent as raw materials. Due to the doping of nitrogen and silicon elements, the surface of CDs contains not only oxygen-containing functional groups, but also alkyl hydrophobic chains, showing amphiphilic characteristic. The micro molecular structure and elemental composition of CDs were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and other tests. The antibacterial behavior of CDs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was studied by the disk antibacterial method, plate colony, scanning electron microscopy (SEM) and other methods. The biocompatibility of CDs was evaluated by cytotoxicity and hemolysis in vitro. The results proved that CDs possessed the average particle size of 1.75 nm and the negative surface potential of −2.71 mV. For E. coli and S. aureus, the minimum bactericidal concentrations of CDs were 500 μg/mL and 400 μg/mL, respectively. These co-doped CDs also possessed the ability to inhibit biofilm formation. The antibacterial mechanism was mainly through the adsorption force to rupture the bacterial membrane and induce the generation of reactive oxygen species in bacterial cells. In addition, CDs exhibited excellent biocompatibility because of their low cytotoxicity and hemolysis, indicating that they can be used as a new material in the antibacterial field.