Bio-inspired Nanoenzyme Synthesis and Its Application in A Portable Immunoassay for Food Allergy Proteins.

Nanozymes as a cost-effective and robust enzyme mimic have attracted widespread attention in the development of novel analytical methods. Herein, a new nanozyme-enhanced surface-enhanced Raman scattering (SERS) immunoassay platform was successfully developed using a peroxidase-mimicking nanozyme to replace the natural enzymes as a catalytic label of the enzyme-linked immunosorbent assay for the detection of allergy proteins. In this platform, the peroxidase-mimicking nanozymes as a catalytic label could catalyze the oxidation of the Raman-inactive reporter [i.e., leucomalachite green (LMG)] to generate Raman-active malachite green (MG) with H2O2. Moreover, the produced MG Raman signal was further enhanced by the formed Raman "hot spot" through MG-induced gold nanoparticle aggregation, which could be recorded by a portable Raman spectrometer. On this basis, the established nanozyme-enhanced SERS immunoassay showed improved accuracy, high sensitivity, and good selectivity and was used for accurate quantification of α-lactalbumin (α-LA). With this method, α-LA could be detected with a limit of detection as low as 0.01 ng/mL. Moreover, the method was also verified by performing in food samples and showed satisfactory recoveries and high reliability. This study not only provides insight into the use of a nanozyme to establish new analytical methods but also broadens the applications of nanozymes in a food safety assay.