Joint trauma results in the production of inflammatory cytokines that stimulate the secretion of catabolic enzymes which degrade articular cartilage. Molecular fragments of the degraded articular cartilage further stimulate inflammatory cytokine production with this process eventually resulting in post-traumatic osteoarthritis (PTOA). The loss of aggrecan is considered an early step in the progression of PTOA. Aggrecan, composed of a core protein linked to sulfated glycosaminoglycans (GAGs), associates with hyaluronic acid (HA) via a link protein. The fragmentation of aggrecan allows diffusion of its anionic GAGs out of the cartilage and results in the loss of compressive strength in articular cartilage. Binding to HA within aggrecan-depleted cartilage and restoring the tissue anionic charge has the potential to restore the osmotic pressure responsible for the compressive strength of articular cartilage. Presented here, we conjugated the HA-binding peptide GAHWQFNALTVRGSG functionalized with a hydrazide (GAH-Hyd) to anionic hollow nanoparticles (hNPs). The hNPs are composed of: N-isopropyl acrylamide (NIPAm), N, N′-bis (acryloyl) cystamine (BAC), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), and acrylic acid (AAc). Reaction of AAc with GAH-Hyd resulted in GAH functionalized hNPs (GAH-hNPs). Increasing the molar ratio of GAH to AAc resulted in increased peptide conjugation to the hNPs. Nanoparticles conjugated with roughly 19 GAH peptides, termed 19 GAH-hNP, bound to HA in solution and increased the dynamic viscosity by 94.0% compared to free HA solution treated with unconjugated hNPs. Moreover, 3 mm diameter, full thickness, aggrecan-depleted (AD) cartilage explants treated with 0.10 mg of 19 GAH-hNP restored the compressive strength to healthy cartilage levels, 95.9 ± 16.2 kPa compared to 123.7 ± 26.5 kPa, respectively, six days after a single dose of the therapeutic. AD explants treated with 0.10 mg of 19 GAH-hNP inhibited the degradation of articular cartilage shown by a 180.09% decrease in chondroitin sulfate (CS) release from cartilage explants into media compared to untreated-AD control, and had 409.03% more collagen type II and 597.58% more GAG content than untreated-AD explants. Finally, fluorescent hNP conjugated with GAH were retained within the joint space of rats for up to 7 days. The 19 GAH-hNP therapeutic presented here was able to slow ECM degradation in AD cartilage explants and restored the compressive strength of damaged cartilage. This therapeutic shows promise as a localized treatment for PTOA.

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