Natural and long-term preservable anticoagulant property of SiO and TiO bilayer films.

INTRODUCTION

Titanium dioxide (TiO2) films have been widely studied as blood-contacting materials, but their positively charged surface and low density of surface hydroxyl (-OH) groups result in poor intrinsic anticoagulant properties. Furthermore, TiO surfaces readily adsorb carbon-containing contaminants from the environment, causing a rapid decline in anticoagulant performance during storage. Thus, improving TiO's intrinsic anticoagulant properties and extending its shelf-life remain challenging.

METHODS

We fabricated a bilayer film by depositing a ∼40 nm silica (SiO2) overlayer onto TiO using unbalanced magnetron sputtering. Surface properties (hydrophilicity, surface charge, and contaminant adsorption) and anticoagulant performance (platelet adhesion after storage) of the resulting SiO/TiO bilayer were characterized.

RESULTS

The SiO/TiO bilayer exhibited long-lasting hydrophilicity, a net negative surface charge, minimal adsorption of carbonaceous contaminants, and a high surface -OH group content. These characteristics are attributed to the formation of interfacial Si-O-Ti bonds, which in turn led to significantly enhanced anticoagulant properties. Notably, after 15 weeks of storage, platelet surface coverage on the bilayer was less than 30% of that on a TiO-only film, indicating greatly improved long-term hemocompatibility.

DISCUSSION

By maintaining a hydrophilic, clean surface with abundant surface -OH groups, the SiO/TiO bilayer achieved superior intrinsic anticoagulant performance that was preserved over long-term storage. This bilayer approach addresses key limitations of TiO, suggesting that SiO/TiO coatings are a promising alternative to pure TiO films for blood-contacting devices.