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

The successful inclusion of hydrated sodium calcium aluminosilicate clay (H SCAS) in diets for the prevention of aflatoxicosis in animals has led to th e investigation of other sorbents that bind mycotoxins. Unfortunately, in v itro studies are not always predictive of in vivo results. In the current s tudy, three previously established in vitro methods: single-concentration s orption. isotherms and chemisorption index (C-alpha) were compared as metho ds for predicting the adsorption of aflatoxin B-1 (AfB(1)) from solution by four sorbents: HSCAS, charcoal, clinoptilolite and sand. In addition, a ga strointestinal (GI) model was utilized to measure adsorption. Finally, maiz e was included in modified isotherm studies to examine interactions. As sup ported by published in vivo studies, HSCAS proved efficacious in all testin g methods (>99% bound in single-concentration and GI sorption studies, C-al pha = 0.89, Q(max) = 0.26 mol kg(-1)). Binding of AfB(1) by charcoal was co mparable to HSCAS (>99% bound in single-concentration and GI sorption studi es, C-alpha = 0.78, Q(max) = 0.889 mol kg(-1)) but was hindered in the pres ence of maize as seen by the distribution constant (K-d = 1.19 x 10(6) vers us 1.11 x 10(5)), Under GI conditions, clinoptilolite demonstrated catalyti c activity not observed in the other methods. Results indicate that the GI model is a rapid and more physiologically relevant method of screening sorb ents. 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 te sting in animals. (C) 2001 Elsevier Science B.V. All rights reserved.