Core–Satellite Gold Nanoparticle@Silver Nanocluster Nanohybrids for Milk Allergen β-Lactoglobulin Detection Using the Electrochemical Aptasensor

Detecting β-lactoglobulin (β-Lg) with high sensitivity and selectivity is an urgent requirement due to nearly 80% of milk anaphylaxis, such as respiratory tract, skin urticaria, and gastrointestinal disorders, being caused by β-Lg. An ultrasensitive β-Lg electrochemical aptasensor utilizing core–satellite gold nanoparticle@silver nanocluster (AuNPs@AgNCs) nanohybrids as electrocatalysts was developed. First, β-Lg aptamer was anchored on gold electrodes and AuNPs to obtain high selectivity. Aptamer-cDNA-AuNPs conjugation was attached to the functionalized electrode with β-Lg as a “bridge” through the target–ligand interaction. Second, DNA-templated AgNCs were introduced via the hybridization of DNA templates oligonucleotide with cDNA anchored on AuNPs. The formed AuNPs@AgNCs nanohybrids showed enhanced catalytic performance toward the silver deposition reaction. This strategy is demonstrated by determining the oxidation current of produced silver nanoparticles (AgNPs) surrounding AuNPs by β-Lg. A detection limit of 0.87 fg/mL and a linear range of 0.001–1000 pg/mL were obtained. Finally, β-Lg content in food products was analyzed successfully, and RSD of 2.44–8.33% was obtained. The recovery of 87.54–113.70% and RSD of 0.95–9.29% was obtained for standard addition experiments. This proposed aptasensor exhibits excellent sensitivity, selectivity, reproducibility, and stability and has good practical application capability for complex food matrices.