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Drug Substance and Excipient Characterization
Published in Dilip M. Parikh, Handbook of Pharmaceutical Granulation Technology, 2021
Parind M. Desai, Lai Wah Chan, Paul Wan Sia Heng
Conventional DSC has a major limitation; if a glass transition temperature occurs in the same temperature range as another transition, for example, water or solvent loss, the two events cannot be separated. This limitation may be overcome by employing modulated temperature DSC (MTDSC), where the measurements are conducted using sine wave temperature programs defined by underlying heating rate, amplitude, and period. The heat capacity change associated with the glass transition temperature can be separated from the heat flow changes caused by melting, drying, and solvent loss. By use of the phase angle curve produced from the MTDSC data analysis, very small changes in specific heat can be detected, thereby increasing the sensitivity of the method. Based on thermal behavior, MTDSC can differentiate the amorphous and polymorphic forms of material with much greater clarity. One of the disadvantages of this method is that the data analysis and interpretation are more difficult than for DSC. Besides, the experiment process can be much prolonged as much lower heating rates are used.
Versatile Nature of Poly(Vinylpyrrolidone) in Clinical Medicine
Published in P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas, Advanced Studies in Experimental and Clinical Medicine, 2021
K. R. Dhanya, P. Mereena Luke, Sabu Thomas, Didier Rouxel, Nandakumar Kalarikkal
PVP is soluble in all types of organic solvents and under normal conditions and is quite stable. The reason behind this remarked solubility is that they contain both hydrophilic and hydrophobic groups in the chain structure. The inert, hygroscopic, colorless, and temperature resistant behavior of PVP makes it a unique polymer [87, 88]. The glass transition temperature is related with its molecular weight. PVP films are fairly hard and transparent. Binding with natural as well as synthetic resins, PVP forms clear films. Chemically modified PVP are extremely inert in nature. In powder state, it is comparatively stable and if applying temperature on PVP, it becomes yellow in color. PVP is in contact with light, the formation of gelation happens.
Quantification of Cellular Elasticity
Published in Malgorzata Lekka, Cellular Analysis by Atomic Force Microscopy, 2017
Many soft materials, such as foams, dense emulsions, and textured morphologies of liquid crystals, are characterized by the presence of structural disorders on a mesoscopic scale (nanometers to microns) causing slow dynamical material evolution (they are classified as soft glassy materials, SGM, [19]). Their structural organization is thought to be metastable, i.e., out of the equilibrium. On the other hand, such materials exhibit rheological properties—therefore, models originating from the studies of the glass transition can be involved in predicting their rheological properties. The empirical criteria that define this class of materials are as follows [20]:
Preformulation studies of l -glutathione: physicochemical properties, degradation kinetics, and in vitro cytotoxicity investigations
Published in Drug Development and Industrial Pharmacy, 2020
Mengyang Liu, Manisha Sharma, Guo-Liang Lu, Naibo Yin, Murad Al Gailani, Sree Sreebhavan, Jingyuan Wen
Figure 4(b) shows the DSC curve of pure GSH, which has an endothermic peak at 195 °C corresponding to its melting temperature [28]. It followed with several small endothermic peaks at 210 °C, indicating the decomposition of GSH. The cooling cycle also confirmed the completed decomposition of GSH, as there are no recrystallisation peaks in cooling procedure. However, there was no exothermic peaks detected between 25 °C and its melting point, which indicates that the glass transition temperature (Tg) did not exist for GSH. Glass transition is defined as the reversible transition in amorphous materials or amorphous regions within semi-crystalline materials, from a hard and relatively brittle ‘glassy’ state into a viscous or rubbery state with increasing temperature [29]. The absence of Tg in the DSC curve indicates the crystalline nature of GSH, supporting the morphology characterization as described above.
Physical stability of dry powder inhaler formulations
Published in Expert Opinion on Drug Delivery, 2020
Nivedita Shetty, David Cipolla, Heejun Park, Qi Tony Zhou
DSC is another solid-state characterization technique which measures the glass transition temperature (Tg) and helps in the identification of melting, crystallization, degree of crystallinity and thermal transition phenomena. Glass transition temperature is the temperature at which a transition from a ‘glassy state’ to a ‘rubbery state’ occurs in an amorphous material. The unique advantage of the DSC technique is its rapid analysis time and that it requires only a nominal sample. However, two major disadvantages of using DSC for measuring Tg are its relatively low sensitivity and the possibility that multiple thermal events may occur and overlap or interfere with the determination of the glass transition [183]. To overcome these limitations of conventional DSC, the modulated DSC (mDSC) was introduced more than two decades ago and has been used to characterize amorphous solids [184]. Both DSC and PXRD can quantify moderate-to-high levels of amorphous materials whereas DVS is more sensitive and can detect very low amounts of amorphous content [48].
Gel network comprising UV crosslinked PLGA-b-PEG-MA nanoparticles for ibuprofen topical delivery
Published in Pharmaceutical Development and Technology, 2019
Ipek Eroglu, Merve Gultekinoglu, Cem Bayram, Acelya Erikci, Samiye Yabanoglu Ciftci, Eda Ayse Aksoy, Kezban Ulubayram
The DSC analysis has revealed that glass transition temperature (Tg) for all the formulations were above the body temperature and this makes this systems suitable for drug delivery purposes. Tg of PLGA-b-PEG nanoparticles and PLGA-b-PEG gel network was found to be 43 °C and ≈52 °C, respectively. The UV crosslinking of nanoparticles resulted in the shift of Tg to a higher temperature due to the decreased interspaces between the polymeric chains. Meanwhile, secondary transitions also shifted to higher temperatures. DSC thermogram of ibuprofen recorded was found to match with the literature findings; a specific exothermic peak at 78 °C was observed and this is specific to ibuprofen. When the DSC thermogram of PLGA-b-PEG-MA nanoparticles was analyzed, effect of methacrylates on the macromolecule has been clearly observed (Figure 6). The transition peaks observed above 105 °C were specific to methacrylates whiles the peak shown at 133 °C represents melting peak for PLGA-b-PEG-MA nanoparticles. In addition to this, endothermic peak recorded at 185 °C represents the decomposition of the structure. The stereotaxic properties of the methacrylayed structure induced the crystallization of the amorphous structure and, therefore Tg was not observed. As a result, UV crosslinking resulted in the shifting of thermal properties and this situation may attributed to the existence of the ibuprofen loaded into the gel network structure in amorphous form instead of a crystal form.