The influence of adsorption incorporation mechanism on the release of isoniazid by montmorillonite

Studies on the use of clay as a drug delivery vehicle have increased in recent years. Its applicability in the pharmaceutical field offers a low-cost solution to addressing drug side effects. Among the drugs that may benefit from a controlled release system is isoniazid (INH), a medication used in tuberculosis treatment. However, to enhance the clay-drug loading capacity and improve sustained drug release, the interaction between clay and drug must be thoroughly understood. This study used montmorillonite (Mtt) to develop Mtt-INH hybrids. Adsorption mechanisms were investigated under two pH conditions. At pH 7, where the drug is in its neutral state, two adsorption phases: the formation of a monolayer (20 mg/g) hybrid (a), followed by multilayer adsorption which can exceed 50 mg/g, hybrid (b) were achieved. At pH 2, where the drug protonates and carries a positive charge, the highest loading capacity of 100 mg/g, (hybrid (c) was achieved at the lowest drug concentration. Different from previous studies, the INH release profile was influenced by the amount adsorbed and the clay-drug interactions. For the hybrids (a) and (c), which correspond to monolayer adsorption, the release profile in intestine pH conditions closely followed the Zero Order Model, (R 2 > 0.93). These hybrids exhibited slower release rates than hybrid (b) consistent with their stronger clay-drug interactions observed during adsorption. In vitro cytocompatibility assays demonstrated that neither pristine clay nor hybrid (c) was cytotoxic to fibroblast cells, supporting the potential of Mtt-based systems for pharmaceutical applications. The results may guide future studies to optimize controlled drug release by considering the expected application and the interactions between the clay-drug system and the pH during the adsorption process.