Nanostructured Coating for Biomaterial Lubrication through Biomacromolecular Recruitment

Biomaterials employed in the articular joint cavity, such as polycarbonate urethane (PCU) for meniscus replacement, lack of lubrication ability, leading to pain and tissue degradation. We present a nanostructured adhesive coating based on dopamine-modified hyaluronan (HADN) and poly-lysine (PLL), which can reestablish boundary lubrication between the cartilage and biomaterial. Lubrication restoration takes place without the need of exogenous lubricious molecules but through a novel strategy of recruitment of native lubricious molecules present in the surrounding milieu. The biomimetic adhesive coating PLL-HADN (78 nm thickness) shows a high adhesive strength (0.51 MPa) to PCU and a high synovial fluid responsiveness. The quartz crystal microbalance with dissipation monitoring shows the formation of a thick and softer layer when these coatings are brought in contact with the synovial fluid. X-ray photoelectron spectroscopy and ConA-Alexa staining show clear signs of lubricious protein (PRG4) recruitment on the PLL-HADN surface. Effective recruitment of a lubricious protein by PLL-HADN caused it to dissipate only one-third of the frictional energy as compared to bare PCU when rubbed against the cartilage. Histology shows that this reduction makes the PLL-HADN highly chondroprotective, whereas PLL-HA coatings still show signs of cartilage wear. Shear forces in the range of 0.07-0.1 N were able to remove ∼80% of the PRG4 from the PCU-PLL-HA but only 27% from the PCU-PLL-HADN. Thus, in this study, we have shown that surface recruitment and strong adsorption of biomacromolecules from the surrounding milieu is an effective biomaterial lubrication strategy. This opens up new possibilities for lubrication system reconstruction for medical devices.