title: TiO2 micro-nano-hybrid surface to alleviate biological aging of UV-photofunctionalized titanium.
abstract: Bioactivity and osteoconductivity of titanium degrade over time after surface processing. This time-dependent degradation is substantial and defined as the biological aging of titanium. UV treatment has shown to reactivate the aged surfaces, a process known as photofunctionalization. This study determined whether there is a difference in the behavior of biological aging for titanium with micro-nano-hybrid topography and titanium with microtopography alone, following functionalization. Titanium disks were acid etched to create micropits on the surface. Micro-nano-hybrid surfaces were created by depositioning 300-nm diameter TiO(2) nodules onto the micropits using a previously established self-assembly protocol. These disks were stored for 8 weeks in the dark to allow sufficient aging, then treated with UV light for 48 hours. Rat bone marrow-derived osteoblasts were cultured on fresh disks (immediately after UV treatment), 3-day-old disks (disks stored for 3 days after UV treatment), and 7-day- old disks. The rates of cell attachment, spread, proliferation, and levels of alkaline phosphatase activity, and calcium deposition were reduced by 30%-50% on micropit surfaces, depending on the age of the titanium. In contrast, 7-day-old hybrid surfaces maintained equivalent levels of bioactivity compared with the fresh surfaces. Both micropit and micro-nano-hybrid surfaces were superhydrophilic immediately after UV treatment. However, after 7 days, the micro-nano- hybrid surfaces became hydrorepellent, while the micropit surfaces remained hydrophilic. The sustained bioactivity levels of the micro-nano-hybrid surfaces were nullified by treating these surfaces with Cl(-)anions. A thin TiO(2) coating on the micropit surface without the formation of nanonodules did not result in the prevention or alleviation of the time-dependent decrease in biological activity. In conclusion, the micro-nano-hybrid titanium surfaces may slow the rate of time-dependent degradation of titanium bioactivity after UV photofunctionalization compared with titanium surfaces with microtopography alone. This antibiological aging effect was largely regulated by its sustained electropositivity uniquely conferred in TiO(2) nanonodules, and was independent of the degree of hydrophilicity. These results demonstrate the potential usefulness of these hybrid surfaces to effectively utilize the benefits of UV photofunctionalization and provide a model to explore the mechanisms underlying antibiological aging properties.
authors.affiliation: Laboratory of Bone and Implant Sciences (LBIS), The Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, UCLA School of Dentistry, Los Angeles, CA, USA.
authors.forename: Fuminori
authors.initials: F
authors.lastname: Iwasa
authors.forename: Naoki
authors.initials: N
authors.lastname: Tsukimura
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Sugita
authors.forename: Rajita Kodali
authors.initials: RK
authors.lastname: Kanuru
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Kubo
authors.forename: Hafiz
authors.initials: H
authors.lastname: Hasnain
authors.forename: Wael
authors.initials: W
authors.lastname: Att
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ogawa
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D018786:Bone Substitutes / Q000737:chemistry*; D002448:Cell Adhesion / Q000502:physiology; D005260:Female; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing / Q000379:methods*; D008856:Microscopy, Fluorescence; D036103:Nanotechnology / Q000379:methods*; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology; D055668:Photochemical Processes; D051381:Rats; D017207:Rats, Sprague-Dawley; D013499:Surface Properties / Q000528:radiation effects; D013997:Time Factors; D023822:Tissue Engineering; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D018786:Bone Substitutes; D014867:Water; C009495:titanium dioxide; D014025:Titanium