Microchip-based electrochemical immunoassay with surface-functionalized polydimethysiloxane channel

Abstract

This thesis reports a microchip-based electrochemical immunoassay with surface-functionalized poly(dimethylsiloxane) (PDMS) channel. While the standard microtiter plate-based immunoassay has required a long incubation time, large sample volumes, and tedious labors, the microchip-based immunoassay gives a solution against those drawbacks by integration of analytical sequences in microscale. In this study, a 3-electrode system for electrochemical detection, fabricated on a glass substrate by photolithography, was assembled to the PDMS channel by plasma treatment. For the effective immobilization of target antibodies, the internal surface of the PDMS channel was chemically modified into the silane monolayer containing the poly(ethyleneglycol) groups, which minimized non-specific binding. Additionally, the low height (50㎛) of the channel enables a rapid immunoassay by reducing the incubation time to 1 min. We chose the mouse IgG as a model analyte for sandwich immunoassay. A low detection limit of 485pg/mL was obtained at 95% confidence level. Furthermore, liquid handling was controlled by a syringe pump preserving a constant channel volume (0.7μL), which was free from tedious separation steps and erroneous volume control. Such an on-chip integration of immunological and enzymatic reactions, amperometric detection, and microfluidic separation system allows performing immunoassays more rapidly, easily, and economically.