Nitrogen-Doped Carbon Quantum Dots for Preventing Biofilm Formation and Eradicating Drug-Resistant Bacteria Infection

Abstract

The development of novel antimicrobial agents is a top priority in the fight against drug-resistant bacteria.Here, we synthesized a green nanoantibiotic, nitrogen-doped carbon quantum dots (N-CQDs) from bis-quaternary ammonium salt (BQAS) as carbon and nitrogen sources. The as-obtained N-CQDs possess high antibacterial activity (>99%) against both methicillin-resistant Staphylococcus aureus (MRSA) and Ampicillin-resistant Escherichia coli bacteria in vitro than some known clinical antibiotics (vancomycin and gentamicin). The N-CQDs can kill MRSA pathogens without inducing resistance, prevent biofilm formation and eliminate established biofilm and persister cells. The treatment of N-CQDs can significantly reduce the amount of bacteria on the infected tissue and accelerate wound healing. The N-CQDs are positively charged, thus enabling them to interact with bacterial cell membrane through electrostatic interaction, leading to severe damage and an increased permeability of the cell membrane, which further promotes the penetration of N-CQDs into the membrane and induces the degradation of DNA by N-CQDs generated reactive oxygen species. The N-CQDs also play a role in obstructing the intracellular metabolic pathways of MRSA. The overall data demonstrate the green nanoantibiotic as an excellent eradicator of biofilm and persister cells as well as a promising antibacterial candidate for treating infections induced by drug-resistant bacteria.

Carbon Quantum Dots Derived from Different Carbon Sources for Antibacterial Applications

“…Hydrothermal synthesis can either be applied as a top-down or bottom-up method to prepare carbon quantum dots, using natural biomass, graphite, polymers or small organic molecules as carbon sources. In hydrothermal synthesis, carbon sources are heated in an aqueous suspension to reaction temperatures ranging from 120 • C to 260 • C. Hydrothermal synthesis of carbon quantum dots is commonly performed in an autoclave, requiring between 4 h and 24 h [22,23,[46][47][48][49][50][51]53]. Hydrothermally obtained carbon quantum dots do not possess a uniform size (Figure 3) and require dialysis or filtration to obtain a uniform size distribution.…”

“…Nitrogen-doped carbon quantum dots, hydrothermally synthesized from a b ternary ammonium salt, for instance, exhibited lower MIC than many common an ics, while inducing less resistance within an MRSA strain than penicillin [47]. Re risk of antimicrobial resistance might arguably be the most promising feature of quantum dots, as many new antimicrobials lose efficacy within shorter and shorte ods of time [97], making the market introduction and clinical application of new an (sub-script), from gentamicin (GENT), induce less resistance of (A) a Gram-positive S. aureus and (B) a Gram-negative E. coli strain than gentamicin used as a carbon source.…”

“…MRSA were exposed to different concentrations of carbon quantum dots. Reproduced with permission from Ref [47],. copyright American Chemical Society, 2019.…”

The In Vivo, In Vitro and In Ovo Evaluation of Quantum Dots in Wound Healing: A Review

“…When the bacteria were exposed to QDs, the microbial membrane disrupt due to the high production of reactive oxygen species (ROS) which triggers significant lipid peroxidation on membrane [ 57 ]. The combination of QDs with polymer deems to have high antibacterial properties towards micro-organisms e.g., S. aureus even inhibits the growth of different drug-resistant bacteria e.g., Methicillin-resistant Staphylococcus aureus (MRSA) [ 60 ].…”

“…This review has stated that the antibacterial properties of QDs have a strong reaction towards both gram-negative and gram-positive bacteria [ 60 ]. However, antibacterial properties of QDs are proven higher towards gram-positive bacteria in comparison with gram-negative bacteria.…”