A New End‐Point for ELISA Titrations

Abstract

This report describes a new ELISA procedure based on end‐point titrations. This end‐point ELISA takes advantage of the change of color intensity that occurs when peroxidase‐containing wells of an ELISA plate are revealed with diaminobenzidine–nickel and further intensification with silver: as antibody concentration and, therefore, peroxidase concentration, decreased, the color became stronger in some wells and, afterwards (i.e., at lower antibody and peroxidase concentrations), the color faded toward clear background. It is proposed that the reciprocal of the sample dilution at which the color intensifies can be used as a measure of the sample antibody content. This report verifies the validity and precision of that procedure.

Keywords:

• ELISA
• End‐point
• Silver enhancement
• Diaminobenzidine
• Poly(lys, phe)
• Immunoglobulin measurement

Acknowledgment

This work was supported by a fellowship (Project No. BSO 2000‐0661) from the Spanish Ministry of Education.