Extended release of 6-aminopenicillanic acid by silanol group functionalized vermiculite

Abstract

The present study aimed to improve capability of vermiculite for extended release ofdrug such as: 6-Aminopenicillanic acid (6-APA). For this purpose, functionalization of vermiculite (VMT) was done by utilizing silanol through hydrolyzing of tetraethoxysilane. The synthesized samples characterized through the XRD, FTIR and BET analyses. The Maximum obtained 6-APA absorption capacity of VMT-Si was 243.9 mg/g, which was higher than other clays. The equilibrium studies demonstrate that drug absorption on VMT and VMT-Si is homogeneous and heterogeneous, respectively. Kinetic studies have been performed by applying reaction based models (such as: pseudo-first-order and pseudo-second-order) and diffusion based models (such as: Boyd, intra-particle diffusion and mass transfer models), which indicates the chemisorption interaction of both aforementioned compounds. The in-vitro release profile of VMT showed a release of about 52% after 5 hours. Whereas, the in-vitro release profile of 6-APA from VMT-Si showed substantially less release of 70% after 7 hours compare to VMT. The maximum obtained release amount of antibiotic (6-APA) per each gram of VMT-Si-6APA and VMT-6APA was 167 mg and 45 mg, respectively. Release kinetic studies show that the release mechanism of 6-APA is controlled by the diffusion process based on Fick's law. In conclusion, vermiculite functionalization with silanol, reduced the rate of drug release and increased the amount of released 6-APA.