Synthesis and characterization of montmorillonite/mannetite nano-composite as a drug carrier system

Porous nanocomposites with high surface area are of great interest in many areas due to their excellent properties. In particular, these products, which contain magnetite nano-particles (MNP) in their structure, have the potential to be used in many areas (chemical, environmental, pharmaceutical, cosmetic, etc.) as adsorbent, catalyst and controlled release carrier system due to their magnetic targeting, high thermal and chemical stability and controlled release capabilities. In the first stage of this study, two different clay ores, containing mainly montmorillonite (Mt), from the Reşadiye/Tokat and Kalecik/Ankara regions were purified by using mineral beneficiation techniques such as sedimentation, centrifuge (falcon gravity separator: FGS) and flotation. In the second stage, mesoporous montmorillonite/magnetite nanocomposites (Mt-Man NK) were produced as a function of tetraethylorthosilicate (TEOS) and cetyltrimethylammonium bromide (CTAB) concentrations. MNP synthesized by chemical co-precipitation method and Mt clay (Reşadiye clay) were used as starting materials for Mt-Man NK production. The silica source TEOS was used to coat the surface of Mt clay and MNPs with amorphous silica, and the cationic surfactant CTAB was used to form pores on silica coated surfaces.The surface of Mt-Man NK prepared under optimum conditions was also modified by aminopropyltriethoxysilane (APTES), and a second nanocomposite Mt-Man-N2 NK was produced. In the third and final stage, the loading (adsorption) performance of 5-Fluorouracil (5-Fu), a cancer drug active substance, to nanocomposites was explored. In the loading experiments, the effects of pH, contact time and 5-Fu initial concentration on the 5-Fu loading capacity were investigated. After 5-Fu loading studies were completed, 5-Fu release profiles and kinetics of loaded nanocomposites were also investigated. In vitro release profiles were examined in three different parameters as gastric media (pH 1.2 phosphate buffer), intestinal media (pH 7.4 phosphate buffer) and magnetic field effect for three replications at 37 oC. Some of the obtained results are given below. Almost all of the gangue minerals (feldspar, calcite, clinoptilolite, opal, quartz, and mica) having particle size >5 µm were removed from the raw ores by using only one stage sedimentation, flotation or centrifuge (FGS) techniques, and purified clay samples were obtained. While the beneficiation degrees obtained in all three methods were almost the same, the highest values in terms of beneficiation yield (68.75% and 81.25% for two Mt clays) were obtained by FGS. Depending on the varying CTAB and TEOS concentration, pore size of Mt-Man NK changed partially while surface area changes were in high levels. Mt-Man NK product, prepared at optimum conditions (1.0 g of MT, 1.15 g MNP, 2.5 g CTAB, 4 mL TEOS), had a mean particle size of 300 nm, a surface area of 340.81 m2/g, an average pore diameter of 8.24 nm, and 18.74 emu/g magnetization saturation. Maximum 5-Fu loading capacities at optimum conditions (24 h contact time, 25 °C temperature, 4000 mg/L 5-Fu initial concentration, and pH 10) were determined as 59.44 mg/g for Mt-Man and 48.38 mg/g for Mt-Man-N2. In vitro release profiles showed that both nanocomposite formulations exhibited controlled release lasting for about 8 hours under all ambient conditions, and the release profiles can be well modeled by Korsmeyer-Peppas and Hixson kinetics. The cumulative 5-Fu releases were found to vary between 64-71% in different conditions.