Biochemical and aerosol characterization of ricin for use in non‐clinical efficacy studies

Ricin toxin may be used as a biological warfare agent and no medical countermeasures are currently available. Here, a well‐characterized lot of ricin was aerosolized to determine the delivered dose for future pre‐clinical efficacy studies.  Mouse intraperitoneal (IP) median lethal dose (LD 50 ) bioassay measured potency at 5.62 and 7.35 μg/kg on Days 0 and 365, respectively. Additional analyses included total protein, sodium dodecyl sulfate polyacrylamide gel electrophoresis, Western blotting, and rabbit reticulocyte lysate activity assay. The nebulizer aerosol produced consistent concentrations (2.5 × 10 3 , 5.0 × 10 3 , 1.0 × 10 4 , and 1.5 × 10 4  μg/mL) and spray factor values. The aerosol particle size distribution was of sufficient size to deposit in lung alveoli (1.12–1.43 μm).  Ricinus communi s Agglutinin II (RCA 60), prepared at 19 mg/mL in phosphate‐buffered saline, pH 7.8, and stored at −70°C, maintained attributes for toxicity following 1‐year storage and aerosolized consistently.