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.
Highlights
The pollution of heavy metal ions has brought a heavy burden to the environment due to industrialization [1]
Due to the long half-life of Cd2+ accumulated in the body, it can cause the disorder of cell cycle, proliferation, differentiation, DNA replication and repair at the cell level, affect the pathway of apoptosis and interfere with the normal metabolism, and pose a potential risk to human health [5,6,7,8]
A large number of studies show that macromolecular bifunctional chelators are the most ideal couplers such as Ethylene Diamine Tetraacetic Acid (EDTA) and its derivatives [35]
Summary
The pollution of heavy metal ions has brought a heavy burden to the environment due to industrialization [1]. The heavy metal ions releasing into the environment (such as air, soil, and water) have caused global heavy metal pollution and have attracted worldwide attention due to human activities [2]. Cadmium has attracted much attention due to its strong toxicity and difficult degradation by microorganisms or organic organisms [3]. The main form of cadmium in the environment is Cd2+, and it will migrate into the human body mainly through the enrichment of the food chain [4]. In 2006, the Codex Alimentarius Commission set the international standard value of cadmium contained in polished rice at 0.4 mg/kg [11]. The Codex Alimentarius Commission (FAO/WHO) Expert Committee on Food Additives (JECFA) stipulates that the weekly cadmium intake of adults should be below 5.8 μg/kg [13]. It is critical to monitor the Cd2+ content in food
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