Brush-Like Coatings Provide a Cloak of Invisibility to Titanium Implants.

Orthopedic implants such as knee and hip implants are one of the most important types of medical devices. Currently, the surface of the most advanced implants consists of titanium or titanium-alloys with high porosity at the bone-contacting surface leading to superior mechanical properties, excellent biocompatibility, and the capability of inducing osseointegration. However, the increased surface area of porous titanium provides a nidus for bacteria colonization leading to implant-related infections, one of the main reasons for implant failure. Here, two readily applicable titanium-coatings based on hydrophilic carboxybetaine polymers that turn the surface stealth thereby preventing bacterial adhesion and colonization are developed. These coatings are biocompatible, do not affect cell functionality, exhibit great antifouling properties, and do not cause additional inflammation during the healing process. In this way, the coatings can prevent implant-related infections, while at the same time being completely innocuous to its biological environment. Thus, these coating strategies are a promising route to enhance the biocompatibility of orthopedic implants and have a high potential for clinical use, while being easy to implement in the implant manufacturing process.

Brush-Like Interface on Surface-Attached Hydrogels Repels Proteins and Bacteria.

Interfacing artificial materials with biological tissues remains a challenge. The direct contact of their surface with the biological milieu results in multiscale interactions, in which biomacromolecules adsorb and act as transducers mediating the interactions with cells and tissues. So far, only antifouling polymer brushes have been able to conceal the surface of synthetic materials. However, their complex synthesis has precluded their translation to applications. Here, it is shown that ultrathin surface-attached hydrogel coatings of N-(2-hydroxypropyl) methacrylamide (HPMA) and carboxybetaine methacrylamide (CBMAA) provide the same level of protection as brushes. In spite of being readily applicable, these coatings prevent the fouling from whole blood plasma and provide a barrier to the adhesion of Gram positive and negative bacteria. The analysis of the components of the surface free energy and nanoindentation experiments reveals that the excellent antifouling properties stem from the strong surface hydrophilicity and the presence of a brush-like structure at the water interface. Moreover, these coatings can be functionalized to achieve antimicrobial activity while remaining stealth and non-cytotoxic to eukaryotic cells. Such level of performance is previously only achieved with brushes. Thus, it is anticipated that this readily applicable strategy is a promising route to enhance the biocompatibility of real biomedical devices.