Colorimetric and chemiluminescent dual-readout immunochromatographic assay for detection of pesticide residues utilizing g-C3N4/BiFeO3 nanocomposites.

Graphitic carbon nitride/bismuth ferrite nanocomposites (g-C3N4/BiFeO3 NCs) were synthesized by a facile one step sol-gel combustion method and employed as a peroxidase-like catalyst. Based on the catalytical activity on the luminol-H2O2 reaction, the nanocomposites were utilized as a colorimetric/chemiluminescent dual-readout immunochromatographic assay (ICA) for the multiplexed detection of pesticide residues by utilizing chlorpyrifos and carbaryl as the model analytes. In the proposed protocol, chlorpyrifos antibody and carbaryl antibody were tagged to g-C3N4/BiFeO3 NCs for developing the spatially-resolved multianalyte ICA. After two competitive immunoreactions completed on the ICA test strip, the tracer antibodies were captured by the immobilized antigens on two test lines. The accumulation of g-C3N4/BiFeO3 NCs led to the appearance of brown color, which were observed as a colorimetric and semi-quantitative signal. Furthermore, the g-C3N4/BiFeO3 NCs-driven generation of CL signal was collected as a sensitively quantitative signal after initiating the luminol-H2O2 reaction on the test lines. Under the optimal conditions, the limits of detection of chlorpyrifos and carbaryl were both 0.033ng/mL. The dual-readout ICA was successfully used to detect chlorpyrifos and carbaryl spiked in environmental water and traditional Chinese medicine samples with acceptable recovery values of 80-119% and 90-118%. Due to many advantages including low cost, time efficiency, high sensitivity and good portability, the novel ICA showed great potential in many areas such as drug safety, environmental monitoring and clinical diagnosis.