Nanocomposite Polymers with "Slimy" Surfaces that Refresh Following Abrasion.

Creating polymeric biomaterials with antifouling surface properties that persist after mechanical abrasion is a significant challenge. We report a simple but effective approach based on nanocomposites consisting of a bulk biocompatible polymer, polycaprolactone (PCL), admixed with a minute fraction (1-3 wt %) of nanoparticles consisting of a hyaluronic acid (HA)-PCL graft copolymer (HA--PCL). In a nonaqueous solvent such as chloroform, the HA-PCL graft copolymer adopts a reverse-micelle-like structure with a shell dominated by PCL chains, allowing it to be mixed well with high-molecular-weight PCL in the same solvent and cast into a nanocomposite film. Upon exposure to aqueous buffer, the HA--PCL nanoparticles reveal the hydrophilic chains of HA to face the outside, conferring a hydrophilic "slimy" or "artificial mucus" layer to the bulk PCL film that resists protein and cell adhesion, without altering bulk mechanical properties. After mechanical abrasion, the nanoparticles replenish the newly exposed material surface with HA, sustaining the surface's protein/cell resistance. This approach could apply to a wide range of biodegradable polymers to achieve consistent antifouling capacity in the face of mechanical abrasion.