Facile synthesis of bentonite/biopolymer composites as low-cost carriers for 5-fluorouracil drug; equilibrium studies and pharmacokinetic behavior.

Two types of bentonite/biopolymer composites (bentonite/chitosan (BE/CH) and bentonite/Co-Poly 2-hydroxyethyl methacrylate-methyl methacrylate (BE/HEMA-MMA)) were synthesized after modification of bentonite by an organic surfactant (BE/CTAB). The products were characterized as low-cost carriers for the 5-fluorouracil drug of high loading properties and controlled releasing behavior. The experimental loading results revealed the suitability of BE, BE/CTAB, BE/CH and BE/HEMA-MMA to load 114 mg/g, 230 mg/g, 273 mg/g, and 310 mg/g, respectively. The loading behaviors of BE/CTAB, BE/CH, and BE/HEMA-MMA are of excellent fitting with the Langmuir model. The adsorption energies and the thermodynamic studies revealed a physisorption mechanism (coulombic attractive forces) for the drug molecules. The thermodynamic parameters reflected spontaneous loading reactions of endothermic nature. The releasing profile showed significant enhancement with the formation of bentonite/biopolymer composites to extend for 160 h without attending the complete release either in the intestinal fluid (pH 7.4) or the gastric fluid (pH 1.2) with a preference for BE/HEMA-MMA composite. The inspected pharmacokinetics reflected erosion mechanism for the releasing of 5FU from BE/HEMA-MMA and the releasing properties of it from BE/CTAB and BE/CH controlled by a combination of erosion and diffusion mechanisms.