Surface plasmon resonance detection of ricin and horticultural ricin variants in environmental samples

A rapid, sensitive and robust immunoassay based on a commercial surface plasmon resonance (SPR) instrument (Biacore X) was developed for the detection of ricin in environmental samples. A total of 10 monoclonal antibodies were evaluated for their ability to recognise both a commercial ricin and horticultural ricin variants extracted from six different cultivars of Ricinus communis. Two suitable antibodies (7G12 and TFTA) were identified because of their strong affinity to all six ricin variants. The antibody 7G12 was used as the capture ligand in the SPR system. The assay was linear over a wide range of ricin concentrations (up to at least 750 ng/ml) with a limit of detection of 0.5 ng/ml. The assay was highly reproducible (coefficient of variation was less than 5%), and was able to detect all six ricin variants and environmental samples.