Fabrication of function-switchable surfaces in metallic biomaterials

众所周知，羟基磷灰石(HAP)通过浸泡在模拟体液(SBF)中沉淀在生物活性材料上。研究了在紫外光照射下，二氧化钛和二氧化锆表面生成羟基磷灰石(HAP)的情况。表面生成HAP对热处理和紫外光不敏感。相反，热处理和紫外光照射对二氧化钛表面羟基磷灰石的形成有很大的影响。热处理可以降低二氧化钛表面的羟基密度。经紫外线照射后密度恢复，促进了羟基磷灰石的形成。这意味着二氧化钛表面生物活性的恢复。紫外光在二氧化钛中产生电子-空穴对，迁移到表面的光生空穴排斥溶液中的正电荷离子。因此，连续紫外光照射抑制了羟基磷灰石的形成。这些结果表明，光照射可能会改变二氧化钛中的几种功能。

Hydroxyapatite (HAp) is known to precipitate on bioactive materials by soaking in simulated body fluid (SBF). The formation of HAp on TiO2 and ZrO2 surfaces under ultraviolet (UV) irradiation was investigated. HAp formation on ZrO2 surface was not sensitive to heat treatment and UV irradiation. In contrast, the HAp formation on the TiO2 in SBF was strongly influenced by heat treatments and UV irradiation. Hydroxyl group density on TiO2 surface could be decreased by the heat treatment. Then the density could be recovered by previous UV irradiation, it led to promotion of HAp formation. This means recovery of bioactivity on the TiO2 surface. The UV light produced electron-hole pairs in the TiO2, and the photogenerated holes that migrated to the surface repelled the positively charged ions in the solution. As a consequence, the continuous UV irradiation suppressed the formation of HAp. These results suggest that several functions in TiO2 might be switched by light irradiation.