Rational engineering of ferritin nanocages for targeted therapy of osteoarthritis.

Intra-articular (IA) drug delivery to treat osteoarthritis (OA) is limited by the short retention time of drugs in the joints due to poor specific targeting and non-responsiveness under acidic environment. A cartilage-targeting peptide was engineered to the surface of ferritin nanocages (CT-Fn) and loaded with an anti-inflammatory drug, metformin (Met), via the self-assembling nature of Fn nanocages. It demonstrated that the CT-Fn/Met could specifically bind to type II collagen, leading to the downregulation of catabolic markers of OA and promotion of cartilage-specific makers in IL-1β-induced chondrocytes. IA delivery of CT-Fn/Met prolonged the retention time for 3 weeks and remarkably reduced inflammation. Moreover, better release under acidic conditions which enabling longer retention time of Met after IA delivery in OA joints for one more week. CT-Fn/Met could target and efficiently enter chondrocytes, further inducing prolonged IA accumulation and achieving enhanced therapeutic efficacy for OA treatment.