The use of dynamic vapour sorption methods for the characterisation of water uptake in amorphous trehalose

The use of polymer blends to improve stability and performance of electrospun solid dispersions: The role of miscibility and phase separation

Solid dispersion-based nanofiber formulations of poorly soluble drugs prepared by electrospinning (ES) with a water-soluble polymer, can offer significant improvements in drug dissolution for oral drug administration. However, when hygroscopic polymers, such as polyvinylpyrrolidone (PVP) are used, environmental moisture sorption can lead to poor physical stability on storage. This study investigated the use of polymer blends to modify PVP-based ES formulations of a model poorly soluble drug, fenofibrate (FF), to improve its physical stability without compromising dissolution enhancement. FF-PVP ES dispersions demonstrated clear dissolution enhancement, but poor storage stability against high humidity. Polymer blends of PVP with Eudragit E, Soluplus and hypromellose acetate succinate (HPMCAS), were selected because of the low intrinsic moisture sorption of these polymers. The drug-polymer and polymer-polymer miscibility study revealed that FF was more miscible with Eudragit E and Soluplus than with PVP and HPMCAS, and that PVP was more miscible with HPMCAS than Eudragit E and Soluplus. This led to different configurations of phase separation in the placebo and drug-loaded fibres. The in vitro drug release data confirmed that the use of PVP-Eudragit E retained the dissolution enhancement of the PVP formulation, whereas PVP-Soluplus reduced the drug release rate in comparison to FF-PVP formulations. The moisture sorption results confirmed that moisture uptake by the polymer blends was reduced, but formulation deformation occurred to phase-separated blend formulations. The data revealed the importance of miscibility and phase separation in understanding the physical stability of the ES fibre mats. The findings provide insight into the design of formulations that can provide dissolution enhancement balanced with improved storage stability.

Methods to characterize the structure of food powders – a review

Food powders can exist in amorphous, crystalline or mixed structure depending on the order of molecular arrangement in the powder particle matrices. In food production, the structure of powders has a greatly effect on their stability, functionality, and applicability. The undesirable structure of powders can be accidentally formed during production. Therefore, characterization of powder structure as well as quantification of amorphous–crystalline proportions presenting in the powders are essential to control the quality of products during storage and further processing. For these purposes, many analytical techniques with large differences in the degree of selectivity and sensitivity have been developed. In this review, differences in the structure of food powders are described with a focus being placed on applications of amorphous powders. Essentially, applicability of common analytical techniques including X-ray, microscopic, vapor adsorption, thermal, and spectroscopic approaches for quantitative and qualitative structural characterization of food powders is also discussed.

Physical Stability of Freeze-Dried Isomalt Diastereomer Mixtures

PURPOSE

Isomalt is a sugar alcohol used as an excipient in commercially available solid oral dosage forms. The potential of isomalt as a novel freeze-drying excipient was studied in order to increase knowledge of the behavior of isomalt when it is freeze-dried.

METHODS

Isomalt was freeze-dried in four different diastereomer compositions and its physical stability was investigated with differential scanning calorimetry, Fourier-transform infrared and Raman spectroscopy, X-ray powder diffraction, Karl-Fischer titration and thermogravimetric analysis in order to verify the solid state form of isomalt after freeze-drying and observe any changes occurring during storage in three different relative humidity conditions.

RESULTS

Isomalt was successfully transformed into the amorphous form with freeze-drying and three diastereomer combinations remained stable as amorphous during storage; one of the diastereomer compositions showed signs of physical instability when stored in the highest relative humidity condition. The four different crystalline diastereomer mixtures showed specific identifiable solid state properties.

CONCLUSIONS

Isomalt was shown to be a suitable excipient for freeze-drying. Preferably a mixture of the diastereomers should be used, as the mixture containing only one of the isomers showed physical instability. A mixture containing a 1:1 ratio of the two diastereomers showed the best physical stability in the amorphous form.

Effect of Hydration on Physicochemical Properties of End-Capped PLGA

The objective of this study was to assess the physicochemical effects of hydrating a hydrophobic end-capped poly(lactide-co-glycolide) (PLGA) polymer in the liquid and vapor state. PLGA RG503 polymer was incubated at 37°C in 0.5% polyvinyl alcohol (PVA) solution and at 90% RH. Samples were withdrawn at predetermined intervals and changes to polymer properties like glass transition temperature (Tg), moisture uptake, molecular weight change, and % acid number were determined using differential scanning calorimetry, Karl Fisher titrimetry, gel permeation chromatography, and acid base titrimetry, respectively. Study results showed that Tg was depressed instantaneously upon hydration, indicating that bulk water acted as a plasticizer of hydrophobic end-capped PLGA. Tg values decreased to levels below the incubation temperature when hydrated in 0.5% PVA solution but not in 90% RH. The drop in Tg exhibited a linear relationship (R2>0.99) to the amount of water uptake by the polymer; higher moisture uptake was noted with liquid water. Removal of moisture from the polymer matrix resulted in recovery of Tg, only up to a period of 14 days. Presence of water in liquid or vapor form caused a reduction in molecular weight of the polymer and a corresponding increase in % acid number over the duration of the study.

Localized hydration in lyophilized myoglobin by hydrogen-deuterium exchange mass spectrometry. 1. Exchange mapping

The local effects of hydration on myoglobin (Mb) in solid matrices containing mannitol or sucrose (1:1 w/w, protein:additive) were mapped using hydrogen-deuterium exchange with mass spectrometric analysis (HDX-MS) at 5 °C and compared to solution controls. Solid powders were exposed to D₂O(g) at controlled activity (a(w)) followed by reconstitution and analysis of the intact protein and peptides produced by pepsin digestion. HDX varied with matrix type, a(w), and position along the protein backbone. HDX was less in sucrose matrices than in mannitol matrices at all a(w) while the difference in solution was negligible. Differences in HDX in the two matrices were detectable despite similarities in their bulk water content. The extent of exchange in solids is proposed as a measure of the hydration of exchangeable amide groups, as well as protein conformation and dynamics; pepsin digestion allows these effects to be mapped with peptide-level resolution.