Regulating the Growth Rate of Gold Nanobipyramids via a HCl-NADH-Ascorbic Acid System toward a Dual-Channel Multicolor Colorimetric Immunoassay for Simultaneously Screening and Detecting Multiple Sulfonamides

It is an urgent need to develop simple and high-throughput methods for simultaneously screening and detecting multiple or groups of sulfonamides (SAs) in animal-derived foods since various SAs were alternately used in animal husbandry to avoid generating drug resistance. We herein developed a novel HCl-reduced nicotinamide adenine dinucleotide I (NADH)-ascorbic acid (AA)-mediated gold nanobipyramids (AuNBPs) growth system, which can precisely regulate the growth rate of AuNBPs, to generate two colorful and stable AA-corresponding multicolor signal channels with different sensitivities. Based on the HCl-NADH-AA-mediated AuNBP growth system, we further developed a dual-channel multicolor immunoassay for simultaneously realizing rapid screening and detection of 5 SAs (sulfamethazine, sulfamethoxydiazine, sulfisomidine, sulfamerazine, and sulfamonomethoxine) by using a paper-based analytical device for sensitively and stably reading out the signal and a broad-specificity anti-SAs antibody as a bio-receptor. The developed immunoassay has more color changes, a wider linear range, excellent specificity and stability, and two multicolor signal channels (L-channel and H-channel) with different sensitivities. The H-channel exhibited 7-8 SAs-corresponding color changes and can be used to detect 5 target SAs with a visual detection limit of 0.1-0.5 ng/mL and a spectrometry detection limit of 0.05-0.16 ng/mL. The L-channel exhibited 7-9 SAs-corresponding color changes and can be used to detect 5 target SAs with a visual detection limit of 2.0-6.0 ng/mL and a spectrometry detection limit of 0.40-1.47 ng/mL. The developed immunoassay was successfully used to simultaneously screen and detect low-concentration and high-concentration of target SAs in milk and fish muscle samples with a recovery of 85-110% and an RSD (n = 5) < 8%. The visual detection limit of our immunoassay is much lower than the maximum residue limit of total SAs in edible tissue. All above features make our immunoassay a promising assay for simultaneously realizing the rapid screening and quantitative determination of multiple SA residues in food by bare eye observation. It must be mentioned that our immunoassay may be expended as a general method for the simultaneous visual screening and detection of other drugs using the corresponding antibody as a recognition probe.