A multicolor immunosensor for the visual detection of six sulfonamides based on manganese dioxide nanosheet-mediated etching of gold nanobipyramids.

In reality, various sulfonamides (SAs) were alternately used in animal husbandry to avoid generating drug resistance. Thus, it is crucial to develop simple and high-throughput methods for detecting multiple or groups of SAs to realize rapid screening of total SAs residues in foods. We herein developed a sensitive and efficient MnO2 nanosheets-mediated etching of gold nanobipyramids (AuNBPs), which can generate more vivid color changes, and further fabricated a high-throughput multicolor immunosensor for the visual screening/semi-quantitative detection of 6 different SAs including sulfamethazine (SMZ), sulfamethoxydiazine (SMD), sulfisomidine (SIM), sulfamerazine (SMR), sulfamonomethoxine (SMM) and sulfaquinoxaline (SQ) by using AuNBPs as signal and broad-specificity anti-SAs antibody as a bio-receptor. The immunosensor displays more vivid color changes, and has a lower visual detection limit and excellent specificity. It can be applied to detect as little as 1.0 ng/mL of SMZ, SMD, SMR and 2.0 ng/mL of SIM, SMM, SQ by bare eye observation, and 0.2 ng/mL of above 6 SAs by UV-visible spectrophotometry. The visual detection limit of the immunosensor is much lower than the maximum residue limit of total SAs (100 μg/kg) in edible tissues. The immunosensor was successfully applied to detect SMZ, SMD, SIM, SMR, SMM and SQ in milk with a recovery of 84%-106% and a RSD (n = 5) < 8%. The success of this study provided a promising assay for the on-site rapid screening of SMZ, SMD, SIM, SMR, SMM and SQ in food by bare eye observation. Importantly, the immunosensor may be expended as a general method for the visual screening/semi-quantitative detection of the group of other antibiotics by using the corresponding broad-specificity antibody as a bio-receptor.