Preparation of specific monoclonal antibodies against chelated copper ions

Combination of phenylboronic acid and oligocytosine for selective and specific detection of lead(ii) by lateral flow test strip

Detection of lead (II) in water sources is of high importance for protection from this toxic contaminant. This paper presents the development and approbation of a lateral flow test strip of lead (II) with the use of phenylboronic acid as chelating agent and oligocytosine chain as receptor for the formed complexes. To locate the bound lead (II) on the test strip, phenylboronic acid was conjugated with carrier protein (bovine serum albumin) and applied as a binding line. In turn, the oligocytosine was conjugated with gold nanoparticle to provide coloration of the finally formed complexes (bovine serum albumin - phenylboronic acid - lead (II) - oligocytosine - gold nanoparticle). This combination of two binding molecules provides the «sandwich » assay with direct dependence of label binding from the analyte content. The technique is characterized by high sensitivity (0.05 ng mL^-1) and the absence of cross-reactions with other metal ions which are often satellite in natural waters. The developed lateral flow tests were successfully applied for lead (II) detection in water. Time of the assay was 5 min. The reached parameters confirm efficiency of the proposed technique for rapid and non-laborious testing under nonlaboratory conditions.

Design of immunogens: The effect of bifunctional chelator on immunological response to chelated copper

To produce specific antibodies for the detection and quantification of copper ions, bifunctional chelators (BFCs) are commonly applied in the preparation of copper conjugates. However, some copper-chelator complexes exhibit limited stability under in vivo conditions. In this study, Cu²⁺ was coupled with carrier proteins via three different macrocyclic BFCs: p-SCN-Bn-DOTA, p-SCN-Bn-NOTA, and p-SCN-Bn-TETA. The stability in plasma and the immunogenicity of three copper immunoconjugates were compared. The chelators other than p-SCN-Bn-DOTA were very stable in plasma, with <9% dissociation of Cu²⁺ over 96 h. The immune response varied depending on the choice of chelator; notably, antisera from the Cu²⁺-NOTA-KLH conjugate demonstrated the best reactivity toward chelated Cu²⁺. p-SCN-Bn-NOTA, which showed significant advantages over the other chelators, was used for antibody production. The efficiency of immune-positive hybridoma production was satisfactory, and the resultant monoclonal antibodies (McAbs) 4B7 showed sensitivity (half-maximal inhibitory concentration (IC₅₀) of 8.9 ng/mL) to chelated Cu²⁺, with a working range from 1.21 to 48.9 ng/mL. The recovery of Cu²⁺ from water samples was 85.7-108%, and the intra- and inter-assay coefficients of variation were 4.0-10.1% and 7.1-11.4%, respectively. Compared with previously reported McAb specific to Cu²⁺, DF4, the sensitivity of the newly developed assay was improved 100-fold. The results of this study indicate the utility of NOTA for the efficient generation of highly sensitive McAbs against Cu²⁺.

Preparation of novel monoclonal antibodies against chelated cadmium ions

The detection of cadmium ions using enzyme-linked immunosorbent assays (ELISA) has been reported by several research groups. Because cadmium ions are too small to stimulate the immune system, high molecular weight immunogens of cadmium are constructed using bifunctional chelators. At present, the most commonly used bifunctional chelator for the preparation of antigens for heavy metal ions is 1-(4-isothiocyanobenzyl) ethylenediamine N,N,N',N'-tetraacetic acid (ITCBE). However, the price of ITCBE is high. So we are interested in a cheaper bifunctional chelator, 1-(4-aminobenzyl) ethylenediamine N,N,N',N'-tetraacetic acid (aminobenzyl-EDTA). Here, cadmium ions were conjugated to carrier proteins using aminobenzyl-EDTA to make artificial antigens. Then, several mice were immunized with the antigen. And monoclonal antibodies (MAbs) against cadmium were produced. Spleen cells of immunized mice were fused with myeloma cells. The resulting hybridomas were screened using protein conjugates which were covalently bound to metal-free EDTA or cadmium. Three hybridoma cell lines (A3, E4 and B5) that produced MAbs with high selectivity and sensitivity were expanded for further study. Cross-reactivities with other metals were below 1 %. These antibodies were used to construct competitive ELISAs. The IC50 for A3 was 8.4 μg/l. The detection range and the lowest detection limit using the antibody A3 was 0.394-64.39 and 0.051 μg/l, respectively. Spike-recovery studies in tap water showed that the antibody A3 could be used for cadmium detection in drinking water.

Visual sensor for the detection of trace Cu(II) ions using an immunochromatographic strip

A rapid and simple immunochromatography method based on a gold nanoparticle-labeled monoclonal antibody was developed for the on-site detection of copper (Cu) in water samples. This monoclonal antibody, obtained by a cell fusion technique, recognized the Cu-ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) complex, but not metal-free EDTA, with high sensitivity and specificity. In optimized conditions, the visual limit of detection for qualitative detection of Cu(II) ions was 10 ng/mL and the LOD for semi-quantitative detection decreased to 0.45 ng/mL with the help of a scanning reader system. The detection process was achieved within 10 min with no cross-reactivity from other heavy metal ions. The recovery of the test samples ranged from 98% to 109%. To our knowledge, this antibody-based test strip for Cu(II) ions has not been previously reported. Based on the above results, this strip sensor could be used as an alternative tool for screening heavy metal pollution in the environment.