Surface Hvdroxyl Groups On TiO₂ Nanorods And Their Biological Performance

Surface modifications in micro/nano structure is an efficient way to accelerate osteointegration between metal implant and natural bone.TiO2 nanorods are wildly used as nanostructure for its performance in promoting osteointegration.However,the principle behind this phenomenon is still unknown.In this study,H2Ti3O7 nanorod was used as hydrated TiO2 and Ta2O5 nanorod was used for its similar electronegativity to reveal the influence of surface hydroxyl groups on TiO2 nanorods.The main results are summarized as follows:1.The state of surface hydroxyl groups on TiO2 nanorods and its biological responsesUsing hydrothermal and acid treatment,we prepared H2Ti3O7 nanorods on Ti substrate.After thermal treatment at 500 ?,H2Ti3O7 nanorods turned into TiO2 nanorods without obvious change in morphology.Results of XPS indicated similar surface amount but different states of surface hydroxyl groups on two nanorods.TiO2 nanorods possessed higher terminal hydroxyl ratio of 0.75,showing good absorption capacity on BSA and FN and good cellular responses including cellular adhesion,proliferation and later cellular differentiation.H2Ti3O7 nanorod possessed lower terminal hydroxyl ratio(0.42,higher bridging hydroxyl ratio),which showed good absorption capacity on BSA and FN and good early cellular differentiation.2.The variation of surface hydroxyl groups on TiO2 nanorods and its biological responsesWe prepared TiO2 nanorods and Ta2O5 nanorods with similar morphology on Ta substrate by hydrothermal.The results indicated that the distinctive gradient on zeta potential against pH,corresponding to the deprotonation rate,but not the hydroxyl amount or hydroxylation polarity played a critical role on the cellular osteogenic performance.TiO2 nanorod film with a higher deprotonation rate significantly upregulated the expression of osteogeneses-related gene and protein,comparing to that of Ta2O5 nanorod film.These results might be attributed to that surface with higher deprotonation rate provided more Bronsted acid-base surface sites to react with protein residues,leading to a mild change in conformation of the absorbed proteins and subsequently facilitating to trigger the integrin-focal adhesion cytoskeleton actin transduction pathway.This study,therefore,provides a new insight into the understanding the role of material surface hydroxylation on cellular osteogenic responses.