Cross-linkage urease nanoparticles: a high-efficiency signal-generation tag for portable pH meter-based electrochemical immunoassay of lipocalin-2 protein diagnostics.

Abstract

An innovative signal-transduction tag based on cross-linked urease nanoparticles (CLENP) was designed for thedevelopment of apH meter-based immunoassay of lipocalin-2 (LCN2). The CLENP was synthesized with a typical desolvation method using ethanol as desolvation agent, followed by functionalization with polyaspartic acid. The carboxylated CLENP were used as the signal-generation tags for the labelling of secondary antibodies via the carbodiimide coupling. Upon target LCN2 introduction, a sandwich-type immune reaction was performed between capture antibody-coated plate and the labeled secondary antibody on the CLENP. The conjugated CLENP in the microplate hydrolyzed urea into ammonia (NH4+) and carbonate (CO32-), resulting in the pH change of solution, which was determined witha handheld pH meter. The pH variation was proportional to target concentration in the sample. By monitoring thepH variation of theurea solution, the level of LCN2 at a concentration as low as 5.2pgmL-1was evaluated.ThepH meter-based electrochemical immunoassay can be utilized formass production of miniaturized lab-on-a-chip devices with handheld pH meter, thereby opening new opportunities for protein diagnostics and biosecurity. Graphical abstract An innovative signal-transduction tag based on cross-linked urease nanoparticles was designed for high-efficiency immunoassay of lipocalin-2 with pH meter readout.