Search

Three thermal analytical techniques such as differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) using five heating rates, and DSC-Fourier Transform Infrared (DSC-FTIR) microspectroscopy using one heating rate, were used to determine the thermal characteristics and the dehydration process of aspartame (APM) hemihydrate in the solid state. The intramolecular cyclization process of APM anhydrate was also examined. One exothermic and four endothermic peaks were observed in the DSC thermogram of APM hemihydrate, in which the exothermic peak was due to the crystallization of some amorphous APM caused by dehydration process from hemihydrate to anhydride. While four endothermic peaks were corresponded to the evaporation of absorbed water, the dehydration of hemihydrate, the diketopiperazines (DKP) formation via intramolecular cyclization, and the melting of DKP, respectively. The weight loss measured in TGA curve of APM hemihydrate was associated with these endothermic peaks in the DSC thermogram. According to the Flynn–Wall–Ozawa (FWO) model, the activation energy of dehydration process within 100–150 °C was about 218 ± 11 kJ/mol determined by TGA technique. Both the dehydration and DKP formation processes for solid-state APM hemihydrate were markedly evidenced from the thermal-responsive changes in several specific FTIR bands by a single-step DSC-FTIR microspectroscopy. Keywords: Aspartame (APM) hemihydrate, DSC/TGA, DSC-FTIR, Dehydration, Activation energy, DKP formation

The effect of Povacoat on the solid state characteristics and polymorphic transformation of γ-form of indomethacin (γ-IMC) after solvent co-evaporation via two drying methods was investigated by thermoanalytical and FTIR spectroscopic studies. The types of solvents (water, ethanol, and water:ethanol (1:9 ~ 2:8, v/v)), weight ratios of Povacoat:IMC (4:1 ~ 4:10, w/w), and drying methods (air-drying and microwave-drying) were selected as variables in this study. A physical mixture of Povacoat and γ-IMC was also carried out by neat grinding process. The results indicate that there was no interaction between Povacoat and γ-IMC or no polymorphic change of γ-IMC after the neat co-grinding process. Since Povacoat was only soluble in water or

Self-assembled cyclic peptide nanotubes (cPNTs) have recently drawn particular attention as one of the most intriguing nanostructures in the field of nanotechnology. Given their unique features including high surface area, increased drug loading, environmental stability, enhanced permeation, and modifiable drug release, these hollow tubular structures can be constructed with cyclic di-, tri-, tetra-, hexa-, octa-, and decapeptides with various amino acid sequences, enantiomers, and functionalized side chains and can be applied for antiviral and antibacterial drugs, drug delivery and gene delivery vectors, organic electronic devices, and ionic or molecular channels. Recent publications have presented promising results regarding the use of cPNTs as drugs or biomedical devices. However, there is an urgent need for the further in vivo nanotoxicity and safety testing of these nanotubes to evaluate their suitability in different fields. [ABSTRACT FROM AUTHOR]

Self-assembled cyclic peptide nanotubes (cPNTs) have recently drawn particular attention as one of the most intriguing nanostructures in the field of nanotechnology. Given their unique features including high surface area, increased drug loading, environmental stability, enhanced permeation, and modifiable drug release, these hollow tubular structures can be constructed with cyclic di-, tri-, tetra-, hexa-, octa-, and decapeptides with various amino acid sequences, enantiomers, and functionalized side chains and can be applied for antiviral and antibacterial drugs, drug delivery and gene delivery vectors, organic electronic devices, and ionic or molecular channels. Recent publications have presented promising results regarding the use of cPNTs as drugs or biomedical devices. However, there is an urgent need for the further in vivo nanotoxicity and safety testing of these nanotubes to evaluate their suitability in different fields. [ABSTRACT FROM AUTHOR]

Purpose The effect of Soluplus on the solid-state characteristics and physical transformation of indomethacin (IMC), saccharin (SAC), IMC-SAC physical mixture, and the previously prepared IMC-SAC co-crystal was investigated after solvent evaporation via air-drying process. Methods Soluplus with γ-IMC or SAC (weight ratio= 1:1) was respectively prepared by completely dissolving both components in acetone by ultrasonication, and then evaporated via air-drying process. Soluplus was fully co-dissolved with the previously prepared IMC-SAC co-crystal (procedure I) or completely dissolved together with IMC-SAC physical mixture (procedure II) in acetone by ultrasonication, and then evaporated through air-drying process. The physical stability of both Soluplus/IMC-SAC systems was also carried out under accelerated storage conditions. All the samples were determined by thermoanalytical and FTIR spectroscopic studies with spectral curve-fitting technique. Results Soluplus caused the amorphous formation of IMC or SAC in the Soluplus solid dispersion, in which the intermolecular hydrogen bonding interaction between SAC and Soluplus occurred. Although Soluplus did not influence the co-crystal formation between IMC and SAC in the solid dispersion, the polymorphic transformation and physical stability of Soluplus/IMC-SAC solid dispersion were markedly influenced by procedures I and II after evaporation via air-drying process. Conclusion Soluplus influences the amorphous or crystalline IMC-SAC co-crystal formulated in the solid dispersion prepared by procedure I or II via air-drying process. The amorphous IMC-SAC co-crystal in the Soluplus solid dispersion prepared by procedure I gradually transformed to a crystalline IMC-SAC co-crystal after storage at 40 ± 2 °C/75 ± 5 % RH conditions for 28 days, whereas the crystalline IMC-SAC co-crystal in the Soluplus solid dispersion prepared by procedure II via air-drying process maintained a long-term storage stability. [ABSTRACT FROM AUTHOR]