Improving the lubricity of commercial mucins via conjugation with catechol-like molecules

There is a range of diseases related to the insufficient lubrication of tissue surfaces. Typically, this occurs as a consequence of the reduced or incomplete production of the macromolecular key components of the respective biolubricant. Thus, developing substitute macromolecules to mitigate friction (and pain resulting thereof) in poorly lubricated joints, on the eyes, or in the oral cavity is an important task in the field of biomaterials science. To date, commercially available biomacromolecules such as hyaluronic acid (HA) and porcine gastric mucin (PGM) have mostly been in the focus of biolubrication research. However, their ability to reduce friction and surface damage generation is limited, which calls for novel approaches. Here, we create chemical modifications of commercial PGM by conjugating different catechol-like molecules (Levodopa (L-Dopa), 3,4,5-trihydroxybenzamide (THBA), or tannic acid (TA)) to the glycoprotein. Whereas solutions comprising unmodified PGMs exhibit poor lubricity, the conjugates show significantly improved surface adhesion and lubrication properties, with the TA–PGM conjugate performing the best. This particular conjugate also mitigates wear formation on PDMS and articular cartilage surfaces equally well as lab-purified porcine gastric mucin and, on hydrophilic surfaces, provides lubricity that even outperforms that of solutions comprising chemically intact, in-lab purified mucins. Our findings pave the way towards the production of a highly versatile biolubricant that can have a broad range of biomedical applications: as a biocompatible viscosupplement in osteoarthritic joints, as a lubricant additive after knee or hip implant surgery, as a component for artificial tear fluids, or for the treatment of xerostomia.