Development of colorimetric immunochromatographic assay based on different morphologies of gold nanoparticles for the detection of triadimefon.

Triadimefon (TDF) is a highly effective, low toxicity, broad-spectrum triazole fungicide with strong systemic absorption. Excessive residues in tobacco and vegetables can affect human health. Therefore, it is urgent to establish a simple, rapid, and sensitive detection method for residual analysis of TDF in tobacco and vegetables. In this study, colloidal gold nanoparticles (Au NPs), gold nanoflowers (Au NFs), and gold nanorods (Au NRs) were synthesized and combined with anti-TDF monoclonal antibodies (mAb) to prepare probes for immunochromatographic strips (ICS). The lowest visual detection limits (vLODs) of the test strips using AuNPs-mAb, AuNFs-mAb, and AuNRs-mAb as probes were 7.8, 15.6, and 15.6 ng/mL, respectively. The three test strips showed no significant cross reactivity with the four structural analogues of tebuconazole, hexaconazole, myclobutanil, and difenoconazole, indicating that all three test strips have good specificity. To assess the presence of 0 and 62.5 ng/mL of TDF, ten test strips were used, and the results showed perfect accuracy with no false positives or false negatives. In addition, three test strips (same batch) were utilized to detect TDF (0 and 62.5 ng/mL) after storage for three months, and the results were still accurate, indicating that all three kinds of test strips have good repeatability and stability. The addition and recovery tests of TDF were conducted on cucumber and tobacco leaf samples (0, 2.5, 17.5, and 65 μg/kg), and the test results revealed that the strips performed with high accuracy. This study established three colorimetric test strips based on three different morphologies of gold nanoparticles, which possess the benefits of quick processing times, high cost-effectiveness, and minimal technical requirements, making them suitable for rapid on-site qualitative detection of TDF.