Comprehensive in vitro and in vivo risk assessments of β-lactam antibiotic and β-lactamase inhibitor loaded chitosan nanoparticles

The safety of using nano-emulsion drug delivery systems is a growing concern. Here, we conducted risk assessments of an innovative combination therapy for multidrug resistant pathogens by encapsulating cephalosporin antibiotics and β-lactamase inhibitors with chitosan nanoparticles (CNAIs) using in vitro human cell lines and an in vivo animal model, Caenorhabditis elegans. The four combinations of CNAIs including two cephalosporin antibiotics (cefotaxime and ceftiofur) with two β-lactamase inhibitors (tazobactam and clavulanate) were engineered as water–oil-water emulsions. CNAIs maintained stable antimicrobial activity in various thermal challenges. CNAIs exerted strong antimicrobial activity but did not cause toxicity in human cell lines measured by cell membrane integrity, mitochondria activity, and reactive oxygen species generation. Reported damage was observed at 8 µg/mL and 16 µg/mL for only two of the four combinations of CNAIs. More importantly, CNAIs at 4 µg/mL did not cause adverse effects on the lifespan of C. elegans. In summary, CNAIs do not cause toxicity at working concentration in vitro and in vivo risk assessments, suggesting that nano-emulsion drug delivery systems can be a new framework for developing treatments for multidrug pathogen infections.