2019 Volume 32 Issue 3 Pages 222-229
Purpose : When titanium (Ti) implants are inserted into bone, the adsorption of proteins at the implant-tissue interface is the first biological response to the implants. Thus, the adsorption behaviors of proteins on Ti must be studied. In this study, we investigated the adsorption of fibronectin on Ti with or without calcium (Ca) ion modification using the quartz crystal microbalance (QCM) technique.
Method : A 27-MHz QCM apparatus was employed. The Ti sensor for the QCM measurement was treated with CaCl2 aqueous solution, and a Ti sensor with Ca ion modification (Ca-Ti) was obtained. Ti and Ca-Ti surfaces were characterized by atomic force microscopy, surface roughness measurements, contact angle against water, and X-ray photoelectron spectroscopy (XPS). The adsorption of human plasma fibronectin on the Ti or Ca-Ti sensor was monitored by the QCM technique. The decrease in the frequency was monitored until 60 min after fibronectin injection, and the amount of fibronectin adsorbed on each surface (⊿m) was calculated using the Sauerbrey's equation. By curve fitting for the ⊿F curve against the adsorption time, the apparent reaction rate, Kobs, was obtained.
Results : There were no significant changes in the surface roughness and contact angles between Ti and Ca-Ti. Both sensors have hydrophilic surfaces. XPS measurements confirmed the presence of Ca on the Ca-Ti sensor. The Ca-Ti sensor exhibited a more rapid and significantly larger decrease in frequency than Ti did, according to the QCM analysis. The Ca-Ti sensor also exhibited a significantly greater amount of adsorbed fibronectin and larger Kobs values than those of Ti.
Conclusion : Ca ion plays a significant role in fibronectin adsorption on Ti. The modification of Ca ion not only enhanced the adsorption of fibronectin on the Ti surface but also progressed the initial adsorption rate of fibronectin to Ti. The adsorption of fibronectin in living tissue conditions proceeds through Ca ion bridge adsorption.
