Three dimensional simulation on binding efficiency of immunoassay for a biosensor with applying electrothermal effect

Abstract

In this work, we perform three dimensional finite element simulations on the binding reaction kinetics of the commonly used analyte–ligand protein pairs, namely, C-reactive protein (CRP) and anti-CRP, in a reaction chamber (microchannel) of a biosensor. For the diffusion limited binding biomolecular pairs, due to the slower transport speed of the analyte and the faster reaction rate of analyte–ligand complex, diffusion boundary layers often develop on the reaction surface. To enhance the performance of a biosensor by accelerating the transport speed, a non-uniform AC electric field is applied to induce the electrothermal force to stir the flow field. The swirling flow in the fluid can accelerate the transport of the analyte to and from the reaction surface and hence enhance the association and dissociation of analyte–ligand complex. Four types of biosensors with different arrangements of the geometric locations of the electrode pair and the reaction surface are designed to study the effects of varying geometric configuration on the binding efficiency. The simulation results show that the performance of a biosensor can be better improved by placing the electrodes and the reaction surface on the same side of the microchannel against the opposite side. For the best case studied in this work, the maximum initial slope of the binding curve can be raised up to 6.94 times (with respect to the field-free value) in the association phase, under applying AC field of 15 V_rms and operating frequency of 100 kHz. Another important result with applying electrothermal effect is that it is feasible to use the slower sample flow in the microchannel to save a lot of sample consumption without sacrificing the performance of a biosensor. Several control factors not studied in our previous works such as the thermal boundary condition and the effect of electrical conductivity are also discussed.