DOI 10.1007/s10856-006-0444-8 Surface behaviour of biomaterials: The theta surface for biocompatibility

Abstract “Biomaterials ” are non-living substances selected to have predictable interactions with contacting biological phases, in applications ranging from medical/dental implants to food processing to control of biofouling in the sea. More than 30 years of empirical observations of the surface be-haviours of various materials in biological settings, when correlated with the contact-angle-determined Critical Sur-face Tensions (CST) for these same materials, support the definition of the “theta surface”. The “theta surface ” is that characteristic expression of outermost atomic features least retentive of depositing proteins, and identified by the bioengi-neering criterion of having measured CST between 20 and 30 mN/m. Biomaterials applications requiring strong bioad-hesion must avoid this range, while those requiring easy re-lease of accumulating biomass should have “theta surface” qualities. Selection of blood-compatible materials is a main example. It is forecast that future biomaterials will be safely and effectively translated directly to clinical use, without re-quiring animal testing, based on laboratory data for CST, protein denaturation, and cell spreading alone.