Streptococcal protein G based fluorescent universal probes and biosynthetic mimetics for Fumonisin B1 immunochromatographic assay

Abstract

Immunochromatographic assay (ICA) plays an important role in the detection of chemical pollutants in food. During the construction of conventional ICA for small molecules, labeling the antibody directly may effect the binding properties of antibody to target antigen. In addition, chemical synthesis of hapten-conjugtes, especially for toxic haptens, may face problems such as complex operations, high inter-batch error, and environmental pollution. In this work, using the detection for mycotoxin fumonisin B1 (FB1) as a model system, the immunochromatographic assay based on fluorescent universal probes and biosynthetic mimetics was established. Biosynthetic mimotope peptide-MBP fusion protein (F15-MBP) was used as a substitute of chemical synthetic FB1-conjugates. Quantum dots nanobeads (QBs) labeled streptococcal protein G (SPG, which can bind to the fragement crytallizable of antibody) was used as a universal signal probe. The antibody and biosynthetic mimetics of coating antigen were sprayed on the conjugate pad and test line, respectively. Under the conditions of optimization, the visual limit detection (vLOD) for FB1 can reach up to 125 pg/mL within 10 min, compared with conventional chemical synthesized FB1-conjugates, when there was a drop of nearly 25 times. The spiked sample (wheat, rice, and corn) with FB1 can be found when the concentration is greater than 1.25 μg/kg. The specificity, repeatability, and stability are confirmed using nagative samples and in accordance with spiked experiments. Furthermore, the novel concept might provide potential applications to a general method for multiplex immunochromatographic assay of various toxic small molecules without steps for labeling antibodies and avoiding synthesis of toxic mycotoxin conjugates.