Bacterial biofilms are highly antibiotic resistant microbial cell associations that lead to chronic infections. Unlike free-floating planktonic bacterial cells, the biofilms are encapsulated in a hardly penetrable extracellular polymeric matrix and, thus, demand innovative approaches for treatment. Recent advancements on the development of gel-nanocomposite systems with tailored therapeutic properties provide promising routes to develop novel antimicrobial agents that can be designed to disrupt and completely eradicate preformed biofilms. In our study, we developed a unique thermoresponsive magnetic glycol chitin-based nanocomposite containing d-amino acids and iron oxide nanoparticles, which can be delivered and undergoes transformation from a solution to a gel state at physiological temperature for sustained release of d-amino acids and magnetic field actuated thermal treatment of targeted infection sites. The d-amino acids in the hydrogel nanocomposite have been previously reported to inhibit biofilm formation and also disrupt existing biofilms. In addition, loading the hydrogel nanocomposite with magnetic nanoparticles allows for combination thermal treatment following magnetic field (magnetic hyperthermia) stimulation. Using this novel two-step approach to utilize an externally actuated gel-nanocomposite system for thermal treatment, following initial disruption with d-amino acids, we were able to demonstrate in vitro the total eradication of Staphylococcus aureus biofilms, which were resistant to conventional antibiotics and were not completely eradicated by separate d-amino acid or magnetic hyperthermia treatments.
Keywords: Staphylococcus aureus; biofilm; d-amino acids; hydrogel nanocomposite; iron oxide nanoparticles; magnetic hyperthermia.