Quaternized carbon quantum dots with broad-spectrum antibacterial activity for the treatment of wounds infected with mixed bacteria

Bacterial resistance to antibiotics have become one of the most severe threats in global public health, so the development of new-style antimicrobial agents is urgent. In this work, quaternized carbon quantum dots (qCQDs) with broad-spectrum antibacterial activity were synthesized by a simple green one-pot method using dimethyl diallyl ammonium chloride and glucose as reaction precursors. The qCQDs displayed satisfactory antibacterial activity against both Gram-positive and gram-negative bacteria. In rat models of wounds infected with mixed bacteria, qCQDs obviously restored the weight of rats, significantly reduced the death of rats from severe infection, and promoted the recovery and healing of infected wounds. Biosafety tests confirmed that qCQDs had no obvious toxic and side effects during the testing stage. The analysis of quantitative proteomics revealed that qCQDs mainly acted on ribosomal proteins in Staphylococcus aureus (Gram-positive bacteria) and significantly down-regulated proteins associated with citrate cycle in Escherichia coli (Gram-negative bacteria). Meanwhile, real-time quantitative PCR confirmed that the variation trend of genes corresponding to the proteins associated with ribosome and citrate cycle was consistent with the proteomic results after treatment of qCQDs, suggesting that qCQDs has a new antibacterial mechanism which is different from the reported carbon quantum dots with antibacterial action. Statement of significance With the development of the research on carbon quantum dots, the application of carbon quantum dots in the field of medicine has attracted extensive attention. In this paper, quaternized carbon quantum dots (qCQDs) with antimicrobial activity prepared by specific methods were studied, including antimicrobial spectrum, antimicrobial mechanism and in vivo antimicrobial application. The antimicrobial mechanism of qCQDs was studied by proteomics and RT-qRCR, and the different mechanisms of qCQDs against Grampositive and Gram-negative bacteria were also found. This study provides a research foundation for the application of carbon quantum dots in antimicrobial field, and also expands the application range of carbon quantum dots in medicine field. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Bacterial resistance to antibiotics has become a serious global public health threat, highlighting the urgent need for new antimicrobial agents. In this study, quaternized carbon quantum dots (qCQDs) with broad-spectrum antibacterial activity were successfully synthesized. The qCQDs exhibited satisfactory antibacterial activity against both Gram-positive and Gram-negative bacteria. In rat models of wound infections, qCQDs effectively restored the weight of rats, reduced the mortality rate associated with severe infection, and promoted wound recovery and healing. Biosafety tests confirmed the absence of obvious toxic and side effects during the testing phase. Proteomics analysis revealed that qCQDs primarily targeted ribosomal proteins in Staphylococcus aureus (Gram-positive bacteria) and down-regulated proteins associated with the citrate cycle in Escherichia coli (Gram-negative bacteria). Real-time quantitative PCR confirmed the consistency between the changes in genes corresponding to these proteins and the proteomic results after qCQDs treatment, suggesting a new antibacterial mechanism of qCQDs different from previously reported carbon quantum dots with antibacterial properties.