The effect of heat treatment temperature on phase formation and luminescence properties of calcium magnesium silicate glass-ceramics doped with Sm2O3

Abstract

The transparent glasses of CaO-MgO-Al₂O₃-SiO₂-ZnO system doped with Sm₂O₃ was prepared by conventional melt-quenching method. The obtained glasses were heat treated at a suitable temperature (875?°C–920?°C for 2?h) identified by differential thermal analysis (DTA). Phase formation and microstructure of glass-ceramics were characterized by X-ray diffraction and scanning electron microscopy, respectively. The optical transmission spectra were recorded by UV-Vis spectrophotometer in the wavelength range between 350 and 1000?nm. It was found that the increase in heat treatment temperature reduced the transparency of the glass-ceramics. The luminescence properties were identified by fluorescence spectroscopy. The excitation spectra of Sm₂O₃ doped CaO-MgO-Al₂O₃-SiO₂-ZnO glass-ceramic samples are in wavelength range of 550–750?nm and the emission spectra exhibited a strong orange-red luminescence composed of 562, 599 and 654?nm under excited at 402?nm. The results of XRD studies revealed the occurrence of diopside (CaMgSi₂O₆) and akermanite (Ca₂MgSi₂O₇) phases. The increasing of heat treatment temperature has no effect on the shift of emission spectra.     

Formulation and evaluation of meloxicam oral disintegrating tablet with dissolution enhanced by combination of cyclodextrin and ion exchange resins

Context: The bitter taste of drug is masked by the exchange of ionized drugs with counter ions of ion exchange resin, forming “resinate”. Cyclodextrin reduces the unpleasant taste and enhances the drug solubility by encapsulating drug molecules into its central cavity.

Objective: Oral disintegrating tablets (ODTs) using the combination of ion exchange resin and cyclodextrin was developed, to mask the bitter taste and enhance drug dissolution.

Methods: Meloxicam (MX) was selected as a model drug. Formulations containing various forms of MX (free drug, MX-loaded resin or resinate, complexes of MX and 2-hydroxypropyl-β-cyclodextrin (HPβCD) or MX/HPβCD complexes, and a mixture of resinate and MX/HPβCD complexes) were made by direct compression. The ODTs were evaluated for weight variation, thickness, diameter, hardness, friability, disintegration time, wetting time, MX content, MX release, degree of bitter taste and stability.

Results and discussion: The tablet hardness was ～3?kg/in², and the friability was <1%. Tablets formulated with resinate and the mixture of resinate and MX/HPβCD complexes disintegrated rapidly within 60?s, which is the acceptable limit for ODTs. These results were corresponded to the in vivo disintegration and wetting times. However, only tablets containing the mixture of resinate and MX/HPβCD complexes provided complete MX dissolution and successfully masked the bitter taste. In addition, this tablet was stable at least 6 months.

Conclusions: The combination of ion exchange resin and cyclodextrin could be used in ODTs to mask the bitter taste and enhance the dissolution of drugs that are weakly soluble in water.