UNDERSTANDING THE CHARACTERISTICS OF L-ASCORBIC ACID-MONTMORILLONITE NANOCOMPOSITE: CHEMICAL STRUCTURE AND BIOTOXICITY

Abstract

Following the previous study to intercalate a 5-fluorouracil (5-FU) into the interlayer spacing of montmorillonite (MMT) for colorectal cancer treatment, we selected a safe and non-pathological microorganism, Saccharomyces cerevisiae, as indicator microorganism to proceed risk assessment on MMT for feasibility study. Dose-response analysis from the perspective in toxicology was conducted to reveal the toxicity rankings of MMT, L-ascorbic acid (LAA) and montmorillonite-L-ascorbic acid (MMT-LAA) composites. This study also tended to intercalate LAA into MMT, observing chemical-structure stabilities of LAA-MMT composites. According to infrared spectroscopic analysis via FTIR, the lattice-vibration peaks of the distorted tetrahedron of SiO4 for MMT were ranged in 400-1200 cm−1. X-ray diffraction analysis also addressed the layer spacing changes in the MMT lattice with pH changes. The variation in the [001] d-spacing changed from 12.4 to 19.4 Å with the increased pH, allowing higher intercalation of viable compounds (e.g., LAA) for controlled-release applications. Compared to MMT, LAA, the lowest toxicity (e.g., EC50=3.77°105 ppm ) of the hybrid MMT-LAA also strongly suggested that MMT-LAA composite is safe to be used for further applications. In contrast, the lowest EC0 (0.564 ppm ) suggested the most sensitive characteristics for MMT-LAA composite to induce the toxic response from no-effect condition. MMT is thus feasible for intercalation of LAA in controlled release to pH changes; particularly, MMT-LAA is considered non-toxic for further applications.