Amorphous solid dispersion is an important formulation technology to improve oral absorption of poorly soluble drugs, where crystallization tendency of the active pharmaceutical ingredient (API) must be comprehended well. Crystallization tendency of API can be estimated by observing crystallization during cooling/reheating of the melt. Though the crystallization during cooling/reheating cannot be directly correlated with crystallization tendency during isothermal storage, which is of great interest in pharmaceutical industry, it provides many insights regarding crystallization mechanism. Initiation time for isothermal crystallization can be explained only by a ratio of glass transition and storage temperatures under well-defined conditions, where knowledge on crystallization tendency is important for expecting other influential factors such as surface area. In this article, assessment of crystallization tendency of pharmaceutical glasses and its relevance to pharmaceutical developmental study is introduced.

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The effects of structurally related organic impurities on the molecular dynamics of amorphous sulfamethazine were evaluated using thermal analysis. Sulfanilamide (SNA), sulfamerazine (SMR), and sulfadimethoxine (SDM) were used as virtual impurities of sulfamethazine. The amorphous state was prepared in situ in differential scanning calorimetry by quenching the melted physical mixtures of sulfamethazine and each impurity compound in the differential scanning calorimetry pan. In the following heating process, the glass transition temperatures (T_g) of each were measured. The fragility parameters were estimated from the width of T_g. The T_g of amorphous sulfamethazine with those impurities changed in accordance with the manner set forth in the Gordon–Taylor equation. The fragility parameter slightly increased when a small amount of SNA or SMR was incorporated. Moreover, the probability of a measurement in which crystallization of sulfamethazine was observed above its T_g, increased at a low concentration range of SNA, SMR, or SDM. It was considered that the existence of a small amount of impurity would induce heterogeneity in the molecular density of the amorphous state, which would be associated with the local fluctuation. It was suggested that the change in the molecular dynamics would be related to the probability of crystallization of sulfamethazine.

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Skin is interface between inside of the body and dried environment. Stratum corneum, outermost layer of skin, maintains physical barrier to prevent dehydration and invasion of exogenous substrate. Morphology of stratum ocnruem sometimes compared to “brick-mortal” model. Keratinocyte corresponds to “brick” and intercellular space corresponds to “mortal”. Intercellular space is filled by lipids, such as ceramides, cholesterol and free fatty acids. Those lipids form regular arrangement, so called “lamellar structure”. Lipid lamellar structure is considered to bear the main barrier function of skin. There are two kinds of lamellar structure of intercellular lipids. The periodicity of long lamellar structure is about 13 nm and that of short lamellar structure is about 6 nm. The lateral packing of lamellar structure is known as orthorhombic and hexagonal packing. There exists several phase transition of intercellular lipids such as liquidization of orthorhombic packing, formation and liquidization of high-temperature and liquidization of long and short lamellar. Those phase transition was affected by the administration of components of topical and transdermal formulation. Change in thermotropic behavior of intercellular lipids might be a key factor of promoting activity of skin permeation enhancement of topical and transdermal formulation. To develop effective formulation, observation of phase transition is important to evaluate formulation components.

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While irreversible aggregation or amyloid formation of denatured proteins are well known and studied in detail, the reversible oligomerization (RO) states of some monomeric proteins at high temperature have been recently discovered by DSC analysis. In this article, the RO states of horse cytochrome c and envelope protein domain 3 from dengue 4 virus were reviewed, and the essential points for the DSC analysis for such self-association/dissociation process were briefly introduced. The significance of RO was discussed as a key process for the kinetics of aggregation and/or amyloid formation, and the importance of the concentration dependence check was suggested for DSC analysis even for monomeric proteins.

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Recently, the number of fire accidents of mobile products using lithium-ion batteries has increased year by year. Overcharge is one of serious causes of thermal runaway for lithium-ion batteries resulting in firing, which occurs in abuse or by malfunction of charging equipment. In order to prevent thermal runaway of lithium-ion batteries in the case of overcharge, appropriate thermal management is required with accurate knowledge for heat generation mechanism of lithium-ion batteries under such accident, and calorimetry is an effective method to characterize thermal behaviors of lithium-ion batteries. In this article, some results of calorimetric analysis of commercially available lithium-ion batteries during overcharging are introduced, where the heat generation is practically proportional to the charging current and almost equivalent to the charging electric power. The electrolytic decomposition reaction of the organic solvents with gas generation is the main reaction at the positive electrode in overcharge. It is noteworthy that even in standard charging condition, a similar exothermic reaction proceeds as like overcharging in some degraded batteries, and this might be one of reasons of thermal runaway.

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The gelation of aqueous methylcellulose (MC) solutions containing polyethylene glycol (PEG) occurred in two-steps. First, the gel network was formed by the hydrophobic interaction between MC and PEG at 310-313 K, and then, the gel network was formed between MC chains at 323 K. On the other hand, in the MC hydrogels containing PEG and NaCl, sodium ion assumed to be enclosed by PEG, forming a helix with the hydrophobic groups outward. The sodium ion in the gel was expected to be surrounded by the ether oxygen of PEG as crown ether. The memory of the gel state was kept for 3 days after gelling at room temperature. The period of keeping the memory of the gel state after gelling agreed with the strength of PEG-water interaction. Thermal analysis is effective as a research method for the gelation process of hydrogel which gels by heating and the state analysis of water.

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