Abstract
Polymer-based, injectable systems that can simultaneously deliver multiple bioactive agents in a controlled manner could significantly enhance the efficacy of next generation therapeutics. For immunotherapies to be effective, both prophylactically or therapeutically, it is not only critical to drive the antigen (Ag)-specific immune response strongly towards either T helper type 1 (Th1) or Th2 phenotype, but also to promote recruitment of a high number of antigen-presenting cells (APCs) at the site of immunization. We have recently reported a microparticle-based system capable of simultaneously delivering siRNA and DNA to APCs. Here we present an in-situ crosslinkable, injectable formulation containing dendritic cell (DC)-chemo-attractants and dual-mode DNA-siRNA loaded microparticles to attract immature DCs and simultaneously deliver, to the migrated cells, immunomodulatory siRNA and plasmid DNA antigens. These low crosslink density hydrogels were designed to degrade within 2-7 days in vitro and released chemokines in a sustained manner. Chemokine carrying gels attracted 4-6 folds more DCs over a sustained period in vitro, compared to an equivalent bolus dose. Interestingly, migrated DCs were able to infiltrate the hydrogels and efficiently phagocytose the siRNA-DNA carrying microparticles. Hydrogel embedded microparticles co-delivering Interleukin-10 siRNA and plasmid DNA antigens exhibited efficient Interleukin-10 gene knockdown in migrated primary DCs in vitro.