Nanoparticle-based delivery of DNAzymes to mitigate inflammatory responses in activated macrophages

Macrophages are highly plastic cells that act as key regulators in the inflammatory process by releasing cytokines to facilitate immune cell infiltration, orchestrate various cellular responses, and help clear bacteria and cellular debris. In chronic inflammatory conditions, macrophages fail to polarize from a pro-inflammatory to an anti-inflammatory phenotype, and the constant inflammatory environment leads to an increase in both apoptosis and unprogrammed cellular death cascades that exacerbate the pathology To address this problem, we developed a biodegradable nanoparticle platform (PCaP NP) that encapsulates a nonimmunogenic nucleic acid in the form of a DNAzyme to suppress IRF5 expression, which promotes macrophage depolarization from a pro-inflammatory state. Our system is comprised of three unique components: 1) a calcium phosphate nanoparticle core designed for predictable biodegradability and optimal retention of nucleic acid payloads, 2) an IRF5-specific DNAzyme designed to silence the expression of IRF5 while mitigating adverse immunogenic responses, and 3) a poly(β-amino ester) (PBAE) polymeric coating to aid with endosomal escape, higher cellular interaction and uptake, and reduced NP-degradability at physiological pH. In this work, we have demonstrated the ability to transfect classically activated macrophages, directly suppress IRF5 expression and downstream cytokines, and cause metabolic changes that are indicative of an alternatively activated phenotype. These results suggest that PCaP NP offers a therapeutic approach to modulate inflammatory pathways in pro-inflammatory macrophages using a biodegradable and non-immunogenic platform. • Innovative strategy for reprogramming macrophages to an anti-inflammatory phenotype • PCaP NPs ensure effective cytosolic release and catalytic function of DNAzymes • DNAzymes ensure that catalytic cleavage of target mRNA is both efficient and specific • Ionizable polymer coating allows endosomal escape, preventing degradation of DNAzymes • IRF5 promotes pro-inflammatory macrophages and is downregulated by PCaP NPs