Improvement in Thermal Stability of Sucralose by Y-Cyclodextrin Metal-Organic Frameworks

Purpose To explain thermal stability enhancement of an organic compound, sucralose, with cyclodextrin based metal organic frameworks. Methods Micron and nanometer sized basic CD-MOFs were successfully synthesized by a modified vapor diffusion method and further neutralized with glacial acetic acid. Sucralose was loaded into CD-MOFs by incubating CDMOFs with sucralose ethanol solutions. Thermal stabilities of sucralose-loaded basic CD-MOFs and neutralized CDMOFs were investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and high performance liquid chromatography with evaporative lightscattering detection (HPLC-ELSD). Results Scanning electron microscopy (SEM) and powder Xray diffraction (PXRD) results showed that basic CD-MOFs were cubic crystals with smooth surface and uniform sizes. The basic CD-MOFs maintained their crystalline structure after neutralization. HPLC-ELSD analysis indicated that the CD-MOF crystal size had significant influence on sucralose loading (SL). The maximal SL of micron CD-MOFs (CDMOF-Micro) was 17.5 +/- 0.9% (w/w). In contrast, 27.9 +/- 1.4% of sucralose could be loaded in nanometer-sized basic CD-MOFs (CD-MOF-Nano). Molecular docking modeling showed that sucralose molecules preferentially located inside the cavities of gamma-CDs pairs in CD-MOFs. Raw sucralose decomposed fast at 90(o)C, with 86.2 +/- 0.2% of the compound degraded within only 1 h. Remarkably, sucralose stability was dramatically improved after loading in neutralized CDMOFs, with only 13.7 +/- 0.7% degradation at 90(o)C within 24 h. Conclusions CD-MOFs efficiently incorporated sucralose and maintained its integrity upon heating at elevated temperatures.