Determination of the Immobilization Manner of Amine-Terminated Poly(Ethylene Glycol) Electrodeposited on a Titanium Surface with XPS and GD-OES

Abstract

Poly(ethylene glycol), PEG, is a biofunctional molecule that inhibits the adsorption of proteins. Therefore, the immobilization of PEG on a metal surface is an important step in making metal surfaces biofunctional. The bonding manner of PEG to a titanium surface is significant for the design of PEG-immobilized materials; however, there are few characterization techniques for the determination of the immobilization manner of PEG. In this study, PEG terminated at one or both terminals with amine bases was immobilized on a titanium surface with electrodeposition and immersion. The electrodeposition was carried out with −5 V for 300 s. The immobilization manner of PEG was characterized using X-ray photoelectron spectroscopy (XPS) with an angle-resolved technique and glow discharge optical emission spectroscopy (GD-OES). As a result, not only electrodeposition but also immersion led to the immobilization of PEG onto a titanium surface. However, more terminated amines combined with titanium oxide as an ionic NH-O with electrodeposition, while more amines randomly existed as NH₃⁺ in the PEG molecule with immersion. Moreover, the difference in the amine termination resulted in a different manner of bonding. The PEG terminated at both terminals immobilized in a U shape, and the PEG terminated at one terminal immobilized a brush. Characterization with XPS and GD-OES is useful to determine the immobilization mode of PEG to a solid surface.