Development of a multi-tiered approach to the in vitro prescreening of clay-based enterosorbents

The successful inclusion of hydrated sodium calcium aluminosilicate clay (HSCAS) in diets for the prevention of aflatoxicosis in animals has led to the investigation of other sorbents that bind mycotoxins. Unfortunately, in vitro studies are not always predictive of in vivo results. In the current study, three previously established in vitro methods: single-concentration sorption, isotherms and chemisorption index (Cα) were compared as methods for predicting the adsorption of aflatoxin B1 (AfB1) from solution by four sorbents: HSCAS, charcoal, clinoptilolite and sand. In addition, a gastrointestinal (GI) model was utilized to measure adsorption. Finally, maize was included in modified isotherm studies to examine interactions. As supported by published in vivo studies, HSCAS proved efficacious in all testing methods (>99% bound in single-concentration and GI sorption studies, Cα=0.89, Qmax=0.26 mol kg−1). Binding of AfB1 by charcoal was comparable to HSCAS (>99% bound in single-concentration and GI sorption studies, Cα=0.78, Qmax=0.889 mol kg−1) but was hindered in the presence of maize as seen by the distribution constant (Kd=1.19×106 versus 1.11×105). Under GI conditions, clinoptilolite demonstrated catalytic activity not observed in the other methods. Results indicate that the GI model is a rapid and more physiologically relevant method of screening sorbents. A three-tiered system that includes: (1) an aqueous binding study; (2) a GI study and (3) isotherms (with and without matrix inclusion), may be used to prescreen mycotoxin/sorbent combinations more effectively before testing in animals.