Alginate chitosan microbeads and thermos-responsive hyaluronic acid hydrogel for phage delivery

Bacteriophages are potential alternatives to conventional antibiotics in the treatment of multidrug resistant infections. However, optimal treatment administration protocols are not established. The direct application of bacteriophages in local biomaterials-based carriers offers solutions to many of the limitations of current modalities. In this study, thermo-responsive hyaluronic acid-poly(N-isopropylacrylamide) (HA-pNIPAM) hydrogels and alginate-chitosan microbeads have been developed as bioresorbable local bacteriophage delivery systems designed to enable rapid and delayed phage release, respectively. The long-tailed Staphylococcus aureus phage ISP and the short-tailed Pseudomonas aeruginosa phage LUZ19 were selected as structurally diverse phages to load within both biomaterials. HA-pNIPAM hydrogels were synthesized and their thermo-responsive crosslinking was confirmed after rheological assessment. Alginate microbeads where prepared by ionic-gelation and chitosan surface deposition was confirmed by amine sensitive assays. After embedding phages, their antimicrobial potential was retained when stored at 4 °C. Release of both phages from HA-pNIPAM hydrogels was gradual and consistent over 21 days, whereby, continuous release of the short-tailed LUZ19 was observed for 21 days from the microbeads, while release of the long-tailed ISP portrayed burst-like release during early timepoints, with gradually reducing phage release thereafter. These findings suggest that the release kinetics of phage from biomaterials are impacted by both the biomaterial and the phages themselves. These results highlight the potential of HA-pNIPAM hydrogel and alginate-chitosan microbeads for local delivery of ISP and LUZ19 bacteriophages for both rapid burst release and controlled, extended release.