Surface-enhanced Raman spectroscopy relying on bimetallic Au–Ag nanourchins for the detection of the food allergen β-lactoglobulin

We designed a SERS-based method to detect β-lactoglobulin (β-Lg), a major allergen of milk, utilizing aptamers to specifically anchor β-Lg. The Au–Ag nanourchins with excellent Raman enhancement effects were prepared and modified with a β-Lg aptamer as the capture substrate. By taking advantage of the hybridization of aptamer and Raman reporter molecule (6-Carboxyl-X-Rhodamine: ROX)-labeled complementary DNA (cDNA), when ROX is close to Au–Ag nanourchins, the SERS signal is enhanced. In the presence of β-Lg, aptamer binding to β-Lg induces the dissociation of ROX-cDNA from Au–Ag nanourchins, thereby decreasing the SERS signal. Under optimal conditions, the present bioassay provides a wide detection range of 10 ng/mL to 1000 ng/mL with a detection limit of 0.07 ng/mL. In addition, the established SERS sensor can selectively and accurately identify β-Lg with recovery rates of 93.25–107.0% in milk samples. It provides great potential as a sensitive and reliable detection method against the growing threat of allergens.