Dual functionality nanobioconjugates targeting intracellular bacteria in cancer cells with enhanced antimicrobial activity

Bacterial drug resistance has emerged as a serious global threat mandating the development of novel methodologies that allow facile modulation of antimicrobial action in a controlled fashion. Conjugating antibiotics to nanoparticles helps to meet this goal by increasing the drug’s overall avidity, bioavailability and easier internalisation into mammalian cells, targeting bacteria that otherwise escape antibacterial action by host cell-localisation. We used polymyxin B sulfate (PMB) and sushi peptide as model drugs against Gram-negative bacteria and established their enhanced antimicrobial activity on Escherichia coli (E. coli) cells after conjugation to gold nanoparticles (AuNPs). The efficacy of the bioconjugates was also tested on Salmonella typhi (S. typhi) bacteria infected into cervical cancer cells (HeLa) and further improved through specific targeting via folate receptors. Our results demonstrate significantly lower inhibitory concentration values for sushi-NP assemblies as compared to free drug, especially at optimal drug loading levels. No major cytotoxicity was observed in mammalian cells alone.