Development of a spiral piezoelectric immunosensor based on thiol self-assembled monolayers for the detection of insulin.

A spiral piezoelectric (Pz) immunosensor based on thiol self-assembled monolayers (SAMs) and fabricated with a screw clamp apparatus was developed for quantitative detection of insulin in serum. Anti-human insulin antibody was first modified with sulfosuccinimidyl 6-[3'-(2-pyridyldithio) propionamido] hexanoate (Sulfo-LC-SPDP) to graft the active sulfhydryl groups into antibody molecules. Then, modified antibody molecules were assembled on a gold electrode via covalent bonding to form SAMs as the recognition element of the insulin immunosensor. The response characteristics of the Pz immunosensor, including buffer solution, time-costs, reproducibility and specificity, were also investigated in detail. Coating a Au electrode with SAMs gave better results within 40 min, with a detection range of 2.5 to 80 mIU/L and a coefficient of variance (CV) less than 5%. The stability and reusability of the immunosensor was improved with a mild eluting reagent which successfully removed the bound insulin molecules from the antibody-coated crystal without affecting the immobilized antibody. A comparison study revealed that analytical results of insulin in samples obtained with this immunosensor were in good agreement with those given by the radioimmunoassay. Thus, the proposed Pz immunosensor provided a rapid, sensitive, specific, reusable and reliable alternative for the detection of insulin in clinical laboratory.