Antibody-pair based immunochromatographic sensor for analytical development and onsite monitoring of chromium...

The prevailing chromium contamination in water resources sets an exigency in developing a rapid detection tool with high sensitivity and target-specificity for impactful environmental monitoring. The present study deals with the development and validation of a highly specific immunosensor based chromium detection platform. Primarily, chromium-protein conjugate was prepared, using EDTA (Ethylenediaminetetraacetic acid) as chelating agent and BSA (Bovine serum albumin) as carrier protein. The optimized ratio of chromium, EDTA, and BSA was 1:1:1 at 0.33 mg/ml concentration each. The successful conjugation of Cr-EDTA-BSA was confirmed through SDS-PAGE analysis. The prepared conjugate was immunized into Balb/c mice for the development of polyclonal and monoclonal antibodies. These antibodies were screened and optimized using sandwich ELISA. The optimized experimental concentration was 50 ng per well antigen (Cr-EDTA-BSA) with an antibody dilution of 1:1500 at OD value of 0.75 (450 nm). The assay showed high chromium specificity and less cross-reactivity (<0.6%) with other metal ions, except Fe(II) (1.7%). ELISA depicted 1.38 ng/ml as the limit of detection. ELISA and ICP-MS showed recovery percentage ranging from 93.3%-111.2% and 96%-115.6%, respectively. The coefficient of variation (CV %) ranged from 10.9% to 14.6% and 11.6% to 14.6% in between the above assays respectively. Significant correlation (R² = 0.995) between both the methods were also observed in terms of chromium concentrations detection. Further, antibody pair was integrated to develop an immunochromatographic test (ICT) sensor, which later processed for lab validation using 0-40 ng/ml concentration of chromium in water samples. The visual limit of detection (vLOD) of the developed ICT assay was 10 ng/ml. The integration of targeted monoclonal-polyclonal antibody pairs for the development of immunosensor, is a novel approach adapted so far. Antibody-pair based immunochromatographic sensor offers rapid, onsite and accurate detection and monitoring of chromium in water sources, promoting a sustainable-healthy environmental practice.