Polydopamine coatings enhance biointegration of a model polymeric implant

The biointegration of implants affects their function, stability and safety. Although most research on this topic has focused on bone and other hard tissues, biointegration with soft tissues is important in numerous applications, such as in prosthetic corneas. Here, we have adapted polydopamine-based adhesive surface chemistry to enhance the biointegration with soft tissue of a model polymer—poly(methyl methacrylate) (PMMA), commonly used in prosthetic corneas. Polydopamine coating (PDA) and subsequent modification with the cell-adhesive peptide RGD (PDA-PEG-RGD) significantly enhanced cellular proliferation of corneal epithelial cells and keratocytes without causing excessive secretion of pro-inflammatory cytokines (e.g.IL-6) by either cell type. PDA adhered tightly to collagen gels, while PDA-PEG-RGD and uncoated PMMA did not. PDA's adhesion to collagen was greatly reduced by preincubation in serum. Tissue reaction to both polydopamine-coated surfaces was benign after 45 days of subcutaneous implantation. However, in contrast to the findings with collagen gels, PDA-PEG-RGD bound much more tightly to tissue than did PDA—although both bound better than unmodified PMMA. Polydopamine-based surface chemistries are potentially useful in enhancing tissue integration of implants with soft tissues.