Functionalization of Azide-Terminated Silicon Surfaces with Glycans Using Click Chemistry: XPS and FTIR Study

Efficient functionalization of silicon substrates is important for the development of silicon-based sensors. Organic monolayers directly bonded to hydrogen-terminated silicon substrates via Si-C bonds display enhanced stability toward hydrolytic cleavage. Here, we show that monolayers presenting a high density of terminal azide groups are amenable to bioconjugation with alkynyl-derivatized glycans via a copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition. The prerequisite azide-functionalized silicon surface is fabricated via hydrosilylation of undecylenic acid with hydrogen-terminated silicon substrate followed by reaction of the thus formed monolayer of acid groups with short, bifunctional oligoethylene oxide chains carrying an amine function at one terminus and an azido group at the other. The possibility to functionalize these azido-surfaces with alkynyl-derivatized glycans such as propargyl mannose through a click protocol is demonstrated and evidenced using X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. In addition, the interaction of these mannose-adorned silicon substrates with glycan binding proteins such as Lens culinaris lectin is investigated. The data establishes clearly the specificity of the interaction of this newly fabricated silicon surface for mannose-selective proteins as well as its reusability, thereby demonstrating its potential as a sensor.