Ultraviolet Treatment Overcomes Time-Related Degrading Bioactivity of Titanium

Abstract

The shelf life of titanium implant products, that is, a possible time-related change of their bioactivity, has rarely been addressed. The objective of this study was to examine the bioactivity of newly processed and aged titanium surfaces and determine whether ultraviolet (UV) light treatment of the titanium surface restores the possible adverse effects of titanium aging. Titanium disks, either acid-etched or sandblasted, were used immediately after processing (fresh surface) or after storing in dark for 4 weeks (aged surface). Some disks were treated with UV light for 48 h after 4 weeks of storage. Albumin adsorbed to the aged surfaces was only 15% of that adsorbed to the fresh surfaces during 2-h incubation, whereas UV-treated aged surfaces adsorbed equivalent amount of albumin to that for the fresh surfaces. During 24-h incubation, the number of human mesenchymal stem cells attached to the aged surfaces was less than half of that for the fresh surfaces, whereas UV treatment of the aged surfaces increased the number three times. Proliferation, alkaline phosphatase activity, and calcium deposition of the cells were substantially lower on the aged surfaces than on the fresh surfaces, while those on the UV-treated aged surfaces were higher than on the fresh surfaces. The strength of bone-implant integration evaluated at week 2 of healing in a rat femur model was reduced to half after 4 weeks of titanium aging, whereas UV treatment of the aged implants increased the strength to the level equivalent to or even higher than the freshly prepared implants. Fresh and UV-treated aged surfaces were superhydrophilic, while the aged surface was hydrophobic. The data suggest that bioactivity of titanium surfaces degrades with time and that UV treatment of the aged surface increases the bioactivity over the level of the freshly prepared surface.

Enhancement of adhesion strength and cellular stiffness of osteoblasts on mirror-polished titanium surface by UV-photofunctionalization

“…This time-dependent degradation of biological activity on the titanium surface was statistically correlated with an increase in the occupancy of carbon. In addition, ultraviolet treatment of aged surfaces increased bioactivity to a level greater than that observed on freshly prepared surfaces [34]. UV-treatment resulted in a clear reduction in the atomic occupancy of carbon on the titanium surface (from over 50% to less than 20%), a proven basic premise for bio-activation by UV-photofunctionalization, together with a change from low wettablity to super-hydrophilicity.…”

“…Acta Biomater Our previous studies demonstrated an increase in the occupancy of carbon and a reduction in osteoblast attachment and protein absorption on bulk titanium surfaces over storage-time in a sterile atmosphere after surface preparation including machining and acid-etching, which was termed the "biological aging of titanium" [32][33][34]. This time-dependent degradation of biological activity on the titanium surface was statistically correlated with an increase in the occupancy of carbon.…”

Effect on Osteogenesis of Cleaning Titanium Implants with Ozonated Water

“…Other reported methods of managing carbon compound adhesion are ultraviolet treatment 33) , storage in saline solution 34) , and gamma-ray irradiation 35) . Ultraviolet treatment is reported to cause physicochemical changes such as changing the titanium surface from hydrophobic to hydrophilic 36) , causing the carbon atom ratio to decrease 37,38) . However, this method has drawbacks in that decomposed carbon compounds remain on the surface, high-concentration ozone gas generated by the ultraviolet rays must be removed, and the apparatus is expensive.…”

TiO2 micro-nano-hybrid surface to alleviate biological aging of UV-photofunctionalized titanium

“…The rate and degree of protein adsorption, cell attachment, and cell proliferation decreased by 30%-80% on 4-week-old titanium surfaces compared with new surfaces. [1][2][3] Progressive accumulation of hydrocarbons, and time-related disappearance of hydrophilic properties and electrostatic positivity on titanium surfaces are thought to be responsible for this biological aging. 1,4,5 Currently, there are no effective means to prevent the biological aging of titanium.…”

“…The levels of bioactivity and osteoconductivity of UV-treated titanium surfaces exceeds the levels of newly prepared titanium surfaces. 2,3 UV treatment reverses the time-dependent physicochemical changes of titanium surfaces. 4,5 UV treatment of aged titanium surfaces decomposes hydrocarbons by inducing photocatalytic activity and restores superhydrophilicity.…”