The purpose of the study was to characterize mucosal attachment of a cationized model protein, bovine serum albumin (BSA), onto the various fractions of colonic crypts epithelium in the rat. BSA was labeled with fluorescein isothiocyanate (FITC) and its surface net electric charge was modified from negative to positive. Attachment of the cationized protein (CF-BSA) onto rat colonic epithelium was performed by incubation of colonic everted sacs in medium containing cationized or non-cationized FITC-labeled BSA. Using a nonenzymatic isolation procedure, colonocytes were harvested from five horizontal fractions of the colonic crypts. BSA adhesion to the isolated colonocytes was quantified spectrofluorometrically. In addition, the effect of increasing concentrations of Mg2- on the adsorption of the cationized BSA onto the surface of colonic epithelium was evaluated by measuring its ability to displace the adhered BSA from its binding sites. BSA cationization facilitated protein adherence to the colon epithelium in a crypt depth-dependent manner. The largest extent of adherence was observed in the outer layer (first fraction) of the colon. Binding persisted to approximately half the depth of the crypts. The relation between CF-BSA concentration in the incubation medium and the amount of CF-BSA adsorbed onto the colonic epithelium was exponential in nature. The addition of electrolyte (Mg2+) caused a detachment of the CF-BSA. The adsorption process was characterized by Langmuir's adsorption isotherm. It is concluded that cationized BSA could be useful as a targetable drug platform in cases where the target site is the gastrointestinal epithelium.
Bibliographical noteFunding Information:
The study was supported by research grants from the American‐Israeli Binational Foundation (93‐56 and 98‐00449). The results reported here are included in the dissertation project of Sigal Blau as partial fulfillment of the Ph.D. degree requirements at The Hebrew University of Jerusalem. Abraham Rubinstein is affiliated with the David R. Bloom Center for Pharmacy at The Hebrew University of Jerusalem.
- Cationized bovine serum albumin
- Colonic crypts
- Regional mucoadhesion