Quick, easy, cheap, effective, rugged and safe strategy for quantifying cadmium polluted rice

Novel Latex Microsphere Immunochromatographic Assay for Rapid Detection of Cadmium Ion in Asparagus

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.

Development and optimization of an immunoassay for the detection of Hg(II) in lake water

In this paper, an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) has been developed and optimized to detect Hg(II) in tap water and lake water based on a monoclonal antibody (mAb-A24). Some stabilizing additives (Gelatin, bovine serum albumin [BSA], polyvinyl alcohol [PVA], and polyvinyl pyrrolidone [PVP]) and surfactant (Tween-20) have been investigated thoroughly in the optimization process. Under the optimal condition, the 50% half maximal inhibitory concentration (IC50) and limit of detection (LOD) were 1.68 and 0.079 ng/ml, respectively. These anti-Hg mAbs also have some affinity with methyl mercury (CH3Hg) and with no cross-reactivity with other thirteen metal ions. The developed method has shown satisfactory recovery of Hg(II), ranged between 91% and 116%, from tap water and lake water. Therefore, this immunoassay can be used to detect trace Hg(II) in environment water.

Quantification of Cadmium in Rice by Surface-enhanced Raman Spectroscopy Based on a Ratiometric Indicator and Conical Holed Enhancing Substrates

A surface-enhanced Raman spectroscopy (SERS) based method was developed for the quantification of Cd²⁺ in rice. Gold nano-particles (AuNPs) modified with trimercaptotriazine served as a ratiometric SERS probe for the detection of Cd²⁺. A conical holed substrate was used to further enhance SERS signals, and hence to improve the sensitivity. A calibration model based on the spectral shape deformation quantitative theory was employed to mitigate the influence of variations in the number and distribution of "hot spots". The proposed SERS method was applied to quantitative analysis of Cd²⁺ in three types of rice, and achieved satisfactory quantitative results with accuracy comparable to that of the reference method-inductively coupled plasma mass spectrometry. The limit of detection of the proposed method was estimated to be 8 μg kg^-1. The proposed SERS method has the potential to become a fast screening method for the detection of Cd²⁺ in rice.

Recyclable colorimetric sensor of Cr3+ and Pb2+ ions simultaneously using a zwitterionic amino acid modified gold nanoparticles

In this work, a rapid, simple and sensitive colorimetric sensor for simultaneous (or respective) detection of Cr³⁺ and Pb²⁺ using tyrosine functionalized gold nanoparticles (AuNPs^Tyr) has been developed. Tyrosine, a natural and zwitterionic amino acid, could be as a reducing and capping agent to synthesise AuNPs and allow for the simultaneous and selective detection of Cr³⁺ and Pb²⁺. Upon the addition of Cr³⁺ or Pb²⁺ (a combination of them), the color of AuNPs^Tyr solution changes from red to blue grey and the characteristic surface plasmon resonance (SPR) band is red-shifted to 580nm due to the aggregation of AuNPs. Interestingly, the aggregated AuNPs^Tyr can be regnerated and recycled by removing Pb²⁺ and Cr³⁺. Even after 3 rounds, AuNPs^Tyr show almost the same A_580nm/A_520nm value for the assays of Pb²⁺ and Cr³⁺, indicating the good recyclability of the colorimetric sensor. The responding time (within 1min) and sensitivity of the colorimetric sensor are largely improved after the addition of 0.1M NaCl. Moreover, the AuNPs^Tyr aggregated by Cr³⁺ or Pb²⁺ (a combination of them) show excellent selectivity compared to other metal ions (Cr³⁺, Pb²⁺, Fe²⁺,Cu²⁺,Zn²⁺,Cr⁶⁺,Ni²⁺,Co²⁺,Hg²⁺,Mn²⁺,Mg²⁺,Ca²⁺,Cd²⁺). More importantly, the developed sensor manifests good stability at room temperature for 3months, which has been successfully used to determine Cr³⁺ and Pb²⁺ in the real water samples with a high sensitivity.