Novel Carbon Nanozymes with Enhanced Phosphatase–like Catalytic Activity for Antimicrobial Applications

Abstract

Abstract In this work, Sulfur and Nitrogen co–doped carbon nanoparticles (SN–CNPs) were synthesized by hydrothermal method using the dried beet powder as the carbon source. TEM and AFM images indicated that these SN–CNPs form a round-shape ball with an approximate diameter of 50 nm. The presence of Sulfur and Nitrogen in these carbon-based nanoparticles was confirmed by FTIR and XPS analyses. These SN–CNPs were found to have strong phosphatase–like enzymatic activity. The enzymatic behavior of SN–CNPs follows the Michaelis–Menten mechanism with greater vmax and much lower Km values compared to alkaline phosphatase. Their antimicrobial properties were tested on E. coli and L. lactis, and values of MIC were identified as 47-µg mL–1 and 188-µg mL–1, respectively. SEM and AFM images of fixed and live E. coli cells showed that SN–CNPs strongly interacted with the outer membranes of bacterial cells, which greatly increased the cell surface roughness. The chemical interaction between SN–CNPs and phospholipid modeled using quantum mechanical calculations further support our hypothesis that the phosphatase and antimicrobial properties of SN–CNPs are due to the thiol group on the SN–CNPs, which is a mimic of the cysteine–based protein phosphatase. The present work is the first to report carbon–based nanoparticles with phosphatase activity and propose a phosphatase natured antimicrobial mechanism. This novel class of carbon nanozymes has the potential to be used for effective catalytic and antibacterial applications.