An ultrasensitive sandwich immunoassay with a glucometer readout for portable and quantitative detection of Cronobacter sakazakii

Abstract

Developing portable and low-cost methods for quantitative detection of Cronobacter sakazakii (C. sakazakii) from powdered infant formula plays a significant role in controlling and preventing a range of serious neonatal infections. Here, we reported a novel methodology for C. sakazakii detection using a low-cost, simple, and widely accessible personal glucose meter (PGM) as the readout. The electrochemical immunoassay strategy was based on antibody and glucose oxidase coated silica nanoparticles (SiNP–GO_X–IgG) and antibody functionalized silica-coated magnetic nanoparticles (MNP–IgG). In the process of detecting a positive sample, a sandwich immunocomplex was formed between the MNP–IgG, C. sakazakii and SiNP–GO_X–IgG. Then, the above sandwich composites were dispersed in glucose solution, and the concentration of glucose was measured using the PGM. Under optimal conditions, a linear relationship between the decrease of glucose concentration and the logarithm of C. sakazakii concentration was obtained in the concentration range from 9.0 × 10² to 9.0 × 10⁷ CFU mL⁻¹ with a detection limit of 4.2 × 10¹ CFU mL⁻¹ (S/N = 3). This simple immunoassay holds great potential as an efficient, sensitive and selective point-of-care testing (POCT) tool for C. sakazakii detection.