title: Reusable hydroxyapatite nanocrystal sensors for protein adsorption.
abstract: The repeatability of the adsorption and removal of fibrinogen and fetal bovine serum on hydroxyapatite (HAp) nanocrystal sensors was investigated by Fourier transform infrared (FTIR) spectroscopy and quartz crystal microbalance with dissipation (QCM-D) monitoring technique. The HAp nanocrystals were coated on a gold-coated quartz sensor by electrophoretic deposition. Proteins adsorbed on the HAp sensors were removed by (i) ammonia/hydrogen peroxide mixture (APM), (ii) ultraviolet light (UV), (iii) UV/APM, (iv) APM/UV and (v) sodium dodecyl sulfate (SDS) treatments. FTIR spectra of the reused surfaces revealed that the APM and SDS treatments left peptide fragments or the proteins adsorbed on the surfaces, whereas the other methods successfully removed the proteins. The QCM-D measurements indicated that in the removal treatments, fibrinogen was slowly adsorbed in the first cycle because of the change in surface wettability revealed by contact angle measurements. The SDS treatment was not effective in removing proteins. The APM or UV treatment decreased the frequency shifts for the reused HAp sensors. The UV/APM treatment did not induce the frequency shifts but decreased the dissipation shifts. Therefore, we conclude that the APM/UV treatment is the most useful method for reproducing protein adsorption behavior on HAp sensors.
authors.affiliation: Biomaterials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan; Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Tokyo, Tokyo 152-8550, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Tagaya
authors.affiliation: Biomaterials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan; Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Tokyo, Tokyo 152-8550, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ikoma
authors.affiliation: Biomaterials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Hanagata
authors.affiliation: Department of Applied Physics, Chalmers University of Technology, Göteberg S-41296, Sweden.
authors.forename: Dinko
authors.initials: D
authors.lastname: Chakarov
authors.affiliation: Department of Applied Physics, Chalmers University of Technology, Göteberg S-41296, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Kasemo
authors.affiliation: Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Tokyo, Tokyo 152-8550, Japan.
authors.forename: Junzo
authors.initials: J
authors.lastname: Tanaka
keywords: hydroxyapatite sensor; protein adsorption; quartz crystal microbalance; reusability; thin layer