STUDY OF INCORPORATION AND CHLORHEXIDINE DIACETATE RELEASE FROM COMMERCIAL BENTONITE AND ORGANOPHILIC BENTONITE

Abstract

Purpose: This work presents a simple method to study chlorhexidine diacetate incorporation into commercial bentonite and bentonite grafted with (3-aminopropyl) triethoxysilane (APTES). Methods: To evaluate the degree of CHX incorporation, two parameters were fixed: contact time and CHX concentration. In a typical bath adsorption experiment, 0.5 g of bentonite was placed in glass flasks and submitted to magnetic stirring between 1 to 2880 min; with CHX solution 50 mg/L. The amount of incorporated CHX was estimated by UV-Vis spectroscopy. Results: The system reached equilibrium in about 90 min; there were no changes in the final concentration before this time. In another experiment, highly concentrated CHX solution (200.000 mg/L) was added to 1.0 g of bentonite. X-ray powder diffraction (XRPD), infrared absoption spectroscopy (FTIR), and thermal analysis (TG and DSC) helped to characterize the structure and properties of unloaded and loaded samples. UV-Vis spectroscopy aided monitoring of chlorhexidine loading and release. 87.5 mg of CHX per gram of bentonite was incorporated. The drug release study revealed that 27.5% CHX was released in 48 hours period. Conclusion: All these techniques shown that chlorhexidine molecules accommodated in the basal spacing of the clay. In this condition, maximum chlorhexidine release occurred in aqueous medium (pH near 7) in less than 24h. XRPD revealed the bentonite basal spacing changed after CHX incorporation into the clay, which indicated the presence of CHX in the basal spacing of the solid. The influence of conditions such as pH, temperature on drug release will be assessed in the future.