Influence of smectite clays' pores volume on isoniazid adsorption and release

Clays have been extensively utilized in various fields due to their remarkable adsorption properties. In pharmaceutical and medical applications, they serve as potential excipients in pills. Emerging research demonstrated their effectiveness as vehicles for controlling drug release. Little has been elucidated, however, regarding the optimal clay characteristics for such applications. Therefore, this study aimed to investigate the influence of clay pores volume on the adsorption of isoniazid (INH), a key drug in tuberculosis treatments worldwide. To achieve this, seven clays were investigated to examine the impact of pores volume on the adsorption and release of INH. Chemical characterization of the clays was conducted using X-ray fluorescence (XRF) and Infrared vibrational spectroscopy (IR), while their mineralogical composition was determined through X-ray diffraction (XRD) and their pore volume by BET method via N2 adsorption/desorption isotherms. Additionally, the interaction between clay and INH was evaluated using FT-IR, XRD, and Thermogravimetric Analysis (TGA). Kinetic adsorption studies were performed to determine the time to reach the equilibrium saturation of the clay by the drug, which was found to be around three hours for all clays. By comparing the pore volume of the studied clays, it became apparent that the clay with an optimal pore volume of approximately 0.100 cm3/g exhibited superior adsorption/retention compared to those with lower or higher volumes. Furthermore, in vitro INH release curves were obtained mimicking release conditions in the intestine (pH 7.4) for a duration of 5 h. It was clearly shown that the release of INH from the clays depend on the pore volume. Our results provided valuable insights into the optimal clay characteristics which would enhance the adsorption and release of INH.