Immunosensor for the determination of LDL(Low-density lipoprotein) was developed by using quartz crystal microbalance(QCM) system. LDL is known to be a good indicator for the diagnosis of atherosclerosis and hypercholesterolemia. The immunosensor system consists of flow-through cell, oscillating circuit, oscilloscope, and frequency counter. This was interfaced with personal computer for signal processing via GPIB. An AT-cut quartz crystal where gold was coated as electrode was held in flow-through cell, which was electrically connected to oscillating circuit to determine the resonant frequency. FIA(Flow Injection Analysis) was applied to the QCM system for measurement in liquid phase. Antibody against protein B-100 reacted with the antibody immobilized on the gold electrode of a quartz crystal by covalent coupling via polyethylenimine(PEI) / glutaraldehyde film. Sample containing protein B-100 reacted with the antibody immobilized on the QCM immunosensor. The response of the immunosensor ($F_0$ - $F_1$) was found to be proportional to the protein B-100 concentration from 200 ug/ml to 800 ug/ml. Optimal conditions for the development of immunosensor were also investigated in terms of sensitivity and non-specific binding.
