PHOSPHATASE ACTIVITY OF SULFUR DOPED CARBON DOTS

Abstract

Carbon dots are novel class of carbon nanomaterials which recently have attracted a widespread attention due to their strong fluorescence, low-cost production and easy synthesis methods. They have been used mostly in biosensing, bioimaging and as drug delivery agents. Recently it was found that they can have enzyme mimetic activity and thus can act as nanozymes. Carbon dots exhibit peroxidase activity as well as can act as catalysts in electrocatalysis. In this project, a novel property of carbon dots, phosphatase activity was identified, and the working mechanism was investigated. The nitrogen and sulfur doped carbon dots were synthesized through a hydrothermal reaction using beet as the starting material. Using NBT-BCIP and pNPP as the substrates, the phosphatase of several assays was performed on carbon dots including pH, temperature and inhibition screening. The enzymatic kinetics characteristics were quantitatively analyzed and antimicrobial properties were tested. The as prepared carbon dots showed high reactivity with both substrates and were not affected by various pH and temperature conditions. In addition, carbon dots exhibited strong inhibition against the growth of E. coli, and rather mild inhibition against L. lactis in a dose dependent manner. Thus, the N and S doped carbon dots are likely achieved the phosphatase through the direct participation in the dephosphorylation steps. The antimicrobial effect exhibited on the E. coli bacteria might be based on the phosphatase nature of the carbon dots.