Microfluidic reflectometric interference spectroscopy-based sensing for exploration of protein-protein interaction conditions.

A microfluidic reflectometric interference spectroscopy (RIfS) system was adopted for the investigation of protein-protein interaction (PPI). The influence of reaction conditions (pH and temperature) on the antigen-antibody reaction of alpha-fetoprotein (AFP) and its monoclonal antibody (anti-AFP) as a model of PPI was investigated in real time with a label-free fusion, where anti-AFP was covalently immobilized on the carboxylated silicon nitride sensor chips via amide bonds. Optimal pH and temperature were rapidly found by successive and alternate injections of AFP and the regeneration solution (glycine-HCl, pH 1.

Fabrication of carboxylated silicon nitride sensor chips for detection of antigen-antibody reaction using microfluidic reflectometric interference spectroscopy.

In this study, we report label-free detection of alpha-fetoprotein (AFP), which has been used as a biomarker for hepatocellular carcinoma, by a microfluidic reflectometric interference spectroscopy (RIfS) system adopting a simple halogen light source and an inexpensive silicon-based sensor chip. Introduction of carboxy groups on a silicon nitride sensor chip to immobilize anti-AFP monoclonal antibody (anti-AFP) was carried out simply by immersion in aqueous solution containing triethoxysilylpropylmaleamic acid bearing a carboxy group and a silanol group. The RIfS system with the anti-AFP-immobilized sensor chip was found to give a reversible response through 100 on/off cycles using a regeneration buffer with high reproducibility (coefficient of variation (CV) = 5.