Novel Latex Microsphere Immunochromatographic Assay for Rapid Detection of Cadmium Ion in Asparagus
Naifeng Xu, Qiaojuan Zhu, Jiangxiong Zhu, Jingze Jia, Xinlin Wei, Yuanfeng Wang
Abstract
Recently, concerns about heavy metal cadmium ion (Cd2+) residue in asparagus have been frequently reported, and there is an urgent need to develop an effective, sensitive, and rapid detection method for Cd2+. In this study, we innovatively combined molecular microbiology to carry out the comparative screening of Cd2+ chelators in a green, efficient, and specific way. The knock-out putative copper-transporter gene (pca1Δ) yeast strain with high sensitivity to Cd2+ was first used to screen the Cd2+ chelator, and the optimum chelator 1-(4-Isothiocyanatobenzyl)ethylenediamine-N,N,N,N′-tetraacetic acid (ITCBE) was obtained. Additionally, a rapid latex microsphere immunochromatographic assay (LMIA) was developed, based on the obtained monoclonal antibody (mAb) with high specificity and high affinity (affinity constant Ka = 1.83 × 1010 L/mol), to detect Cd2+ in asparagus. The 50% inhibitive concentration (IC50) of test strip was measured to be 0.2 ng/mL, and the limit of detection (IC10) for qualitative (LOD, for visual observation) and quantitative detection (LOQ, for data simulation) of the test strip was 2 ng/mL and 0.054 ng/mL, respectively. In all, the developed mAb-based LMIA shows a great potential for monitoring Cd2+ in asparagus, even in vegetable samples.