Study on covalent coupling process and flow characteristics of antibody on the surface of immunoassay microfluidic chip

The immune response system of immunoassay microfluidic chips is a dynamic reaction process that continuously sends reactants to the surface of a solid carrier. Signal acquisition results from the heterogeneous immune reactions and reactant transport. Antibody immobilization is the most important part of heterogeneous immune reactions, and reactant transport is reflected in the form of fluid velocity. Here, we reported several surface modification processes on polystyrene substrates that are employed to study the relationship between the antibody immobilization and flow behavior in heterogeneous immune response processes. The antibody was immobilized using covalent grafting. Based on the mechanism of sandwich enzyme linked immunosorbent assay, a fluorescence quantitative detection method was used to evaluate the immune response process. The effects of different surface modification processes on immune response and flow behavior were studied. We identified an optimal flow velocity in the dynamic immune response system in the microfluidic chip. The immune response signal was the strongest when the average flow velocity was approximately 0.2 mm/s in the procalcitonin detection system. Compared with the amino and aldehyde group substrates, the epoxy group substrate has the highest antibody immobilization efficiency; compared with the surface modified by small molecular groups, the introduction of Poly-L-Lysine can increase the amount of antibody immobilization.