Bioinspired Muco-Adhesive Restores Lubrication of Degraded Cartilage

Abstract

Adsorbed lubricious films composed of biomacromolecules, natively present at articulating interfaces, yield ultralow coefficient of friction to maintain normal physiological function. Biolubrication can be impaired due to disease, e.g. osteoarthritis is associated with alteration in synovial fluid and lamina splendens composition which leads to cartilage damage. Lamina splendens is a conditioning film of synovial fluid molecules on the cartilage surface. Patients with osteoarthritis are always given hyaluronic acid (HA) injection to alleviate pain. Pain relief remains temporary because HA is easily squeezed out of the cartilage-cartilage or cartilage-meniscus sliding interface. Here, we describe how natural lubrication on degraded cartilage surface is restored by a bioinspired muco-adhesive biopolymer chitosan catechol (Chi-C). Catechol grafted chitosan (Chi-C) shows high affinity towards lubricin, a mucin-like glycoprotein PRG4, from synovial fluid. Chi-C increased the softness of lamina splendens through PRG4 recruitment, which improved the lubrication in vitro at nanoscale. Next, on an ex vivo degraded cartilage friction system, Chi-C was able to show lubrication restoration at macroscale. This research provides a new key insight in restoration of biolubrication through the use of muco-adhesive molecules, which can increase the conditioning film softness at the articulating tissue surfaces in living system.