Glucoamylase-labeled nanogold flowers for in situ enhanced sensitivity of a glucometer-based enzyme immunoassay

Abstract

Methods based on enzyme labels have been developed for glucometer-based immunoassays, but most involve low sensitivity and are unsuitable for routine use. Herein, we report a simple and sensitive enzyme immunoassay for the determination of neuron-specific enolase (NSE) by using glucoamylase-labeled nanogold flowers (GA-NGFs) for signal amplification. The assay is implemented in a polystyrene microtiter plate with a sandwich-type immunoassay format. In the presence of the target analyte, the sandwiched immunocomplex can be formed in the microplate between capture antibody-functionalized microplate and detection antibody-conjugated GA-NGF. The carried glucoamylase accompanied nanogold flowers can hydrolyze amylopectin in glucose, which can be quantitatively monitored by using a user-friendly personal glucometer (PGM). Under optimal conditions, the PGM signal increased with the increasing target NSE concentration in the dynamic working range of 0.01–30 ng mL⁻¹ with a detection limit of 8 pg mL⁻¹. Importantly, the PGM-based immunoassay also displays good reproducibility, high specificity and comparable method accuracy with the referenced values.