Enzyme-Induced Silver Deposition on Gold Nanorods for Naked-Eye and Smartphone Detection of Acrylamide in Food

Acrylamide is a probable human carcinogen with a wide occurrence in commonly consumed food. Because of the lack of specific antibodies against acrylamide, immunoassays usually measure acrylamide derivates, which require long derivatization times at elevated temperatures. One exception is xanthylacrylamide (XAA), which can be derived from acrylamide at room temperature within 30 min. Here, we present the development of a monoclonal antibody against XAA and a competitive enzyme-linked immunosorbent assay (ELISA) based on the multicolor detection of gold nanorods (AuNRs). The biotinylated monoclonal antibodies bound streptavidin alkaline phosphatase, which induced XAA concentration-dependent silver deposition on the AuNRs. The resulting blue shift of the AuNR surface plasmon resonance peak translated into a strong gray-to-orange color change that could be conveniently distinguished by the naked eye or smartphone color detection. The assay showed a broad linear range (0.3-17.2 ng/mL), a low limit of detection (0.06 ng/mL), and a 3.6-fold sensitivity improvement compared to those of conventional tetramethylbenzidine-based ELISA. The analysis of several different food products showed excellent acrylamide concentration recoveries (84-102%) and confirmed its applicability as an effective tool for routine monitoring of acrylamide in food. Rapid and simple color analysis demonstrated a strong potential for implementation into direct consumer product testing.