Influence of electrical polarization on thrombogenicity of titania nanotubes

Abstract

The development of hemocompatible biomaterials with antithrombogenic surface coatings remains a challenge in cardiovascular applications. There is interest in negatively charged surfaces that inhibit thrombus formation through electrostatic repulsion between the biomaterial surface and negatively charged platelets. Hence, the present study investigated the influence of electrical polarization on the thrombogenicity of titania nanotubes (TNT), which are promising candidates for inhibiting thrombogenicity via surface modification. TNTs were formed on commercially pure titanium plate by the electrochemical anodization technique using platinum as a counter electrode at 60 V for 24 h with two kinds of electrolytes (hydrofluoric acid diluted with dimethyl sulfoxide [D-TNT] or ethylene glycol [E-TNT]) followed by an annealing at 540°C for 3 h in air. Both TNTs were mixture of anatase and rutile, and the D-TNT had a diameter of 108.76 ± 2.55 nm and the E-TNT, 53.833 ± 2.42 nm. The TNTs were electrically polarized at 100 V of DC field and 400°C for 1 h. Water contact angle measurements showed that the non-polarized (0-) TNT surface was hydrophilic whereas the positively (P-) or negatively (N-) polarized TNT surfaces showed high-hydrophilicity. Antithrombogenicity was evaluated using the thrombus coverage area ratio (TCAR) after soaking the TNTs in bovine whole blood. The TCARs for 0-polarized E- and D-TNTs were 5.30 ± 4.34% and 36.3 ± 5.8% and for P-polarized E-TNT and D-TNT were 1.50 ± 0.77% and 2.76 ± 1.07%, whereas no thrombus formation (0 ± 0%) for N-polarized E-TNT and very few thrombus formation (0.12 ± 0.22%) for N-polarized D-TNT. The electrostatic repulsion between the N-polarized E-TNTs and platelets completely inhibits thrombus formation, which cannot be achieved by the nanomorphology and high-hydrophilicity of other TNTs. Hence, N-TNTs formed by electrical polarization are potential candidates for cardiovascular devices, such as artificial heart valves with long-term hemocompatibility.