Alginate-Chitosan Gel Microbeads for PhiKZ Encapsulation as a Model of Bacteriophage Delivery to Combat Pseudomonas...

Wound infections due to antibiotic resistance pose a global public health problem. Phage therapy is a promising approach to address this issue. To improve localization, phage stability, delivery, and antibacterial performance, we propose polymer mix gel microbeads encapsulated with phages as a model for the delivery of phiKZ bacteriophage to combat Pseudomonas aeruginosa. Phages were loaded into the alginate pre-gel under magnetic stirring, with further cross-linking by chitosan and/or Ca²⁺ ions. The obtained gel microbeads were characterized using FTIR and Raman spectroscopy, and their cytotoxicity and antimicrobial properties were evaluated. This study demonstrated the efficient loading of high-titer phage lysate, achieving up to 99% encapsulation efficiency for alginate-chitosan microbeads. The key characteristics of the microbeads include stable physicochemical properties, slow but continuous phage release over 48 h in physiological saline, and low cytotoxicity. The phage-loaded microbeads demonstrated strong in vitro antimicrobial activity against P. aeruginosa PAO1, resulting in mean reductions of 6.9 log₁₀ and 4.8 log₁₀ CFU/mL for alginate and alginate-chitosan formulations, respectively. This corresponded to a decrease in bacterial concentration from approximately 1.1 × 10¹¹ CFU/mL in untreated controls to 1.1 × 10⁵ CFU/mL and 7.7 × 10⁶ CFU/mL for alginate and alginate-chitosan formulations after 3 h of incubation.