Comprehensive detection of ricin following oral exposure: feces as the key diagnostic matrix

Ricin is classified as a Schedule 1 toxin under the Chemical Weapons Convention (CWC) and Category B agent under the Biological and Toxin Weapons Convention (BTWC). Its extreme toxicity, lack of an antidote, and potential for deliberate misuse necessitate rapid detection strategies for effective medical and public health responses. However, information on optimal biological matrices and detection windows following ingestion remains limited. This study evaluated optimal biosamples and detection strategies following oral ricin exposure in mice. Crude and purified ricin were isolated from castor seeds and characterized by SDS-PAGE. Following oral LD₅₀ determination, mice were administered 5 × LD₅₀ doses to simulate severe poisoning. Feces, urine, serum, and liver samples were collected at 2, 4, 8, and 18 h post-exposure. Detection was performed using in-house lateral flow assay (LFA), sandwich ELISA, and immunoblotting, with selected samples validated by cytotoxicity assays and LC-MS/MS to confirm toxin integrity and activity. Feces offered the broadest diagnostic window, with biologically active ricin detected at all time points. Urine contained lower toxin levels but consistently enabled detection, supporting its utility as a non-invasive matrix. Serum ricin was transient, peaking at 2-4 h and often required enrichment to overcome matrix interference. Conversely, liver samples exhibited progressive toxin accumulation, peaking at 18 h, emphasizing their forensic value. These findings delineate ricin toxicokinetics following oral exposure and establish feces as the most reliable matrix for sustained detection. By integrating LFA with confirmatory immunoassays, this study provides a practical framework for early identification and public health preparedness in ricin exposure scenarios.