A bifunctional core–shell gold@Prussian blue nanozyme enabling dual-readout microfluidic immunoassay of food allergic protein

Food allergy has posed a great threat for public health due to its rising prevalence worldwide, and thus sensitive and reliable food allergen monitoring methods is of great significance. In this study, we prepared a bifunctional core-shell gold@Prussian blue nanoparticles (Au@PBNP) nanozyme, which not only could serve as an alternative to natural peroxidase for colorimetric immunoassay, but also act as a unique Raman label in Raman-silent region (1800-2800 cm-1) for SERS analysis. By combining microfluidic device, smartphone, and portable Raman spectrometer, a new smartphone/SERS dual-readout microfluidic immunoassay platform was established for portable detection of food allergic protein (i.e., alpha-lactalbumin (α-LA)). The established method for detection of α-LA showed a LOD of 0.011 ng/mL in a liner range of 0.2-600 ng/mL. Furthermore, this method was also challenged in spiked food samples with good average recoveries, showing a great potential in practical applications.