Abstract:

Objective: To establish a colloidal gold immunochromatographic assay (Cd2+-Strip) for detecting Cd2+ residues
in foods. Methods: Artificial hapten Cd2+-iEDTA was synthesized by using isotrhiocyanobenzyl-EDTA (iEDTA) to chelate
Cd2+. The isothiocyanate method was used to conjugate Cd2+-iEDTA to BSA to obtain the artificial immunogen Cd2+-
iEDTA-BSA. The coating antigen Cd2+-iEDTA-OVA was obtained in the same way. Both ICP-AES and SDS-PAGE were
used to identify Cd2+-iEDTA-BSA. Balb/C mice were immunized with Cd2+-iEDTA-BSA and hybridoma lines that secreted
anti-Cd2+-EDTA monoclonal antibody (mAb) were generated by cell fusion. A Cd2+ test strip was established with Cd2+-
EDTA mAb and its traits were tested. Results: Cd2+-iEDTA-BSA was synthesized successfully and its concentration of
BSA and Cd2+ was 7.1 mg/mL and 191.7 μg/mL respectively. Four hybridoma lines, namely 1A3C11, 2B7D8, 2E10G9,
4F3E7, were screened out and 2E10G9 was found to be the best one. The dissociation constant (Ka) of 2E10G9 was
7.58 × 108 L/mol and its sensitivity (IC50) was 16.3 μg/L, and it had little or no cross-reactivity with other metal ions, except
for Hg2+-EDTA with 18.6%. The qualitative detection of Cd2+ with the Cd2+ test strip could be achieved in 10 minutes, with
a limit of detection (LOD) of 5 μg/L. Its sensitivity was the same as that of competitive ELISA-Kit (Cd2+ ELISA-Kit) and
inductively coupled plasma atomic emission spectrometry (ICP-AES), and its coincidence rate was 100% as compared
with Cd2+ ELISA-Kit and ICP-AES. Conclusion: The high affinity and specificity Cd2+-EDTA mAb has successfully been
generated and used to establish a Cd2+ test strip with high sensitivity, specificity, rapidity and briefness. The test strip can be
used for the rapid detection of Cd2+ residues in foods.

Key words: cadmium ion, immunogen, monoclonal antibody, colloidal gold immunochromatographic assay, rapid detection