Enhanced anti-P. aeruginosa treatment via phage and ciprofloxacin co-loaded particles prepared by electrospraying.

Antimicrobial resistance (AMR) poses a critical global health challenge, contributing to an estimated 1.27 million deaths worldwide due to bacterial infections in 2019. Phages offer a possible solution to this, but alone have been found to be sub-optimal. There can however be great benefits in combining antibiotics and phages to give synergistic treatment. To that end, this study incorporates both ciprofloxacin (cipro) and phages into co-loaded microparticles prepared by electrospraying (ES). With optimized concentrations (0.25 wt% cipro and 50 % v/v phage stock), the resulting phage encapsulation efficiency (EE) reached 29 ± 3 %. Following electrospraying, a modest reduction in phage titer was observed, from 5 × 107 to 1.4 × 107 PFU/mg, suggesting good preservation of phage viability during the electrospraying process. The cipro loading reached 0.20 ± 0.01 %, with an EE of 79.9 ± 2.2 %. In addition to spherical morphology and efficient phage loading, the particles exhibited a rapid initial release of their therapeutic cargo, achieving 98.8 ± 4.0 % of phage release and 93.5 ± 7.0 % of cipro release within 10 min. The combination of half the minimum heat inhibition concentration (MHIC) of cipro (0.3 μg/ml) and 108 PFU/ml phages completely inhibited the growth of Pseudomonas aeruginosa (P. aeruginosa) over 30 h, and a co-loaded particle concentration of 333 μg/ml extended bacterial inhibition for over 40 h. The results provide meaningful guidance for the design and optimization of antibiotic- and phage-loaded microparticles as potential antibacterial formulations for the treatment of bacterial infections.