2020 Volume 33 Issue 2 Pages 159-166
Purpose : The adsorption of proteins onto a Ti implant surface is the first biological event after bone implantation. Thus, the investigation of protein adsorption to Ti is vital for understanding the process of osseointegration. In this study, using the quartz crystal microbalance (QCM) method, we investigated the adsorption of proteins to a Ti surface in two-step adsorption methods.
Method : A 27 MHz QCM apparatus was employed. The following two-step adsorptions of fibronectin (Fn) and albumin (Alb) were investigated : (1) Fn-Alb series : First, the Fn solution was injected into the phosphate-buffered saline (PBS) solution, followed by the Alb solution ; (2) Alb-Fn series : First, the Alb solution was injected, followed by the Fn solution. The frequency decrease was monitored for 60 min after each protein injection. The adsorbed amounts of Fn or Alb in each series were calculated using the Sauerbrey equation. The apparent reaction rate, Kobs, was obtained by curve fitting of the frequency decrease curve. Atomic force microscopy was used to observe the surface appearance and surface roughness of protein-adsorbed sensor surfaces after they were rinsed with double-distilled water.
Results : Fn injection produced greater frequency decrease than Alb injection. Alb-Fn series showed greater frequency decrease 120 min after protein injection than Fn-Alb series. The adsorbed amount of Fn in Fn-Alb series is significantly higher than that of Alb in Alb-Fn series during the first adsorption in each. Moreover, there is a significant difference in the adsorbed amounts of Fn between the first step in the Fn-Alb series and the second step in the Alb-Fn series. There are no significant differences in the adsorbed amounts of Alb between the first step in the Alb-Fn series and the second step in the Fn-Alb series. The first protein adsorption showed significantly greater Kobs values than the second protein adsorption. AFM images showed that after rinsing with water, some Alb remained on the Alb-adsorbed sensor surface, but little Fn was identified. The Alb-adsorbed sensor surface showed significantly greater Sa values than native Ti and Fn-adsorbed Ti surfaces.
Conclusion : The adsorption of Alb influences that of Fn in two-step adsorption. The adsorbed amounts of Fn were enhanced by Alb adsorption, but the adsorbed amounts of Alb were not influenced by Fn adsorption. Fn and Alb adsorption rates were delayed by first protein adsorption, revealing that the first protein adsorption influences the second protein adsorption.
