A Novel Photoelectrochemical Immunosensor for Sensitive Detection of Milk α-Lactalbumin Based on CdWO4 –CdS Heterojunction

Cow milk is an important source of protein, but it is also a food that can cause allergies. In this research, a novel photoelectrochemical immunosensor based on CdWO 4 –CdS type-II heterojunction was constructed for the detection of allergen α -lactalbumin ( α -Lac) in milk. CdWO 4 –CdS heterojunction was synthesized by one-step hydrothermal method. Compared with pure CdWO 4 , the CdWO 4 –CdS heterojunction significantly improved the photocurrent intensity. The polydopamine (PDA) was used as a crosslinking agent to couple basis materials and biomolecules. Ascorbic acid was used as an efficient electron donor to eliminate the photo-generated holes and inhibit the recombination of photo-generated electrons and holes. Under the optimum experimental conditions, the photocurrent intensity reduced linearly with the logarithm of α -Lac concentration ranging from 0.001 ng ⋅ mL − 1 to 10 ng ⋅ mL − 1 and the limit of detection was 0.17 pg ⋅ mL − 1 . The constructed photoelectrochemical immunosensor exhibited excellent stability, selectivity and reproducibility, which provided a novel ideal for sensitive detection of α -Lac and shed light on monitoring of other allergenic proteins in foods.