Curcumin-Loaded High-Charge Swelling Synthetic Mica: Characterization Studies and Stability under Stress Conditions

Curcumin (Cur) is a bioactive compound with various pharmacotherapeutic effects. However, its limited solubility and stability pose challenges for therapeutic applications. Clay minerals, such as montmorillonite (MMT) and high-charge swelling synthetic micas, show promise as drug carriers due to their properties. This study aimed to obtain complexes with clay minerals that could enhance the stability of Cur. MMT, Na-Mica-4, and the latter organofunctionalized with 18-carbon alkylamines (C18-Mica-4) were used as support for Cur. Adsorption studies showed that Na-Mica-4 exhibited the highest percentage of adsorption (60%). Cur-Mica-4 complexes were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (DSC and TGA), specific surface area (BET), pore size and volume determinations, and surface charge determination by zeta potential measurement. The effect of light on Cur and Cur-Mica-4 complexes was also evaluated. Forced degradation studies were performed under hydrolytic, oxidative, photolytic, and thermal conditions to assess the stability and degradation pathways. The FTIR spectra indicated that the enol tautomer mainly formed part of the complexes. BET analysis showed a reduced pore size after adsorption, indicating Cur immobilization. TGA and scanning electron microscopy (SEM) suggested degradation primarily occurring under exposure to sunlight, heat, and ultraviolet light. The effect of acidic and basic conditions on the Cur-Mica-4 complex was evaluated. Under acidic conditions, a decrease in the specific surface area of the complex was observed, suggesting the formation of larger configurational structures. An increase in the specific surface area with a smaller pore size was observed in the basic medium, possibly due to the formation of new structures in the clay minerals, supported by XRD results. These findings indicate that the pH of the medium can significantly influence the structure and stability of the Cur-Mica-4 complex, which could have important implications for its application in specific environments, such as drug delivery systems.