Bioresponsive Microspheres for On-demand Delivery of Anti-inflammatory Cytokines for Osteoarthritis

Despite innovations in surgical interventions, treatment of cartilage injury in osteoarthritic joints remains a challenge due to concomitant inflammation. Obstructing a single dominant inflammatory cytokine have shown remarkable clinical benefits in rheumatoid arthritis, and similar strategies are being suggested to target inflammatory pathways in osteoarthritis (OA). Here we describe the utility of gelatin microspheres that are responsive to arthritic flares, resulting in on-demand, and spatiotemporally controlled release of anti-inflammatory cytokines for cartilage preservation and repair. These microspheres had net negative charge potential to sequester cationic anti-inflammatory cytokines, and the magnitude of the negative charge potential increased with increase in crosslinking density. The enzymatic degradation of the microcarriers was concentration dependent. Release of anti-inflammatory cytokines from the loaded microspheres was directly correlated with the degradation of the gelatin matrix. Exposure of the IL-4 and IL-13 loaded microspheres reduced the inflammation of chondrocytes up to 80%. Hence, the delivery of these microspheres in an osteoarthritic joint can attenuate the stimulation of chondrocytes to secrete catabolic factors including proteinases and nitric oxide. The microsphere format also allows for minimally invasive delivery and is less susceptible to mechanically-induced drug release and are conformant to the intra-articular space. Consequently, bioresponsive microspheres are an effective tool for OA prevention and treatment.