N-Heterocycle Modified Graphene Quantum Dots as Topoisomerase Targeted Nanoantibiotics for Combating Microbial Infections

Developing next-generation antibiotics to eliminate multidrug-resistant (MDR) bacteria/fungi and stubborn biofilms is challenging, because of the excessive use of currently available antibiotics. Herein, the fabrication of anti-infection graphene quantum dots (GQDs) is reported, as a new class of topoisomerase (Topo) targeting nanoantibiotics, by modification of rich N-heterocycles (pyridinic N) at edge sites. The membrane-penetrating, nucleus-localizing, DNA-binding GQDs not only damage the cell walls/membranes of bacteria or fungi, but also inhibit DNA-binding proteins, such as Topo I, thereby affecting DNA replication, transcription, and recombination. The obtained GQDs exhibit excellent broad-spectrum antimicrobial activity against non-MDR bacteria, MDR bacteria, endospores, and fungi. Beyond combating planktonic microorganisms, GQDs inhibit the formation of biofilms and can kill live bacteria inside biofilms. RNA-seq further demonstrates the upregulation of riboflavin biosynthesis genes, DNA repair related genes, and transport proteins related genes in methicillin-resistant S. aureus (MRSA) in response to the stress induced by GQDs. In vivo animal experiments indicate that the biocompatible GQDs promote wound healing in MRSA or C. albicans-infected skin wound models. Thus, GQDs may be a promising antibacterial and antifungal candidate for clinical applications in treating infected wounds and eliminating already-formed biofilms.