Influence of Tricuspid Bioprosthetic Mitral Valve Orientation Regarding the Flow Field Inside the Left Ventricle: In Vitro Hydrodynamic Characterization Based on 2D PIV Measurements

The flow patterns of a prosthetic heart valve in the aortic or mitral position can change according to its type and orientation. This work describes the use of 2D particle image velocimetry (PIV) applied to the in vitro flow fields characterization inside the upper part of a left ventricular model at various heart rates and as a function of two orientations of stented tricuspid mitral bioprostheses. In the ventricular model, each mitral bioprosthesis (27 and 31 mm diameter) was installed in two orientations, rotated by 180°, while the aortic bileaflet mechanical valve (27 mm diameter) remained in a fixed orientation. The results (N = 50) showed changes in the intraventricular flow fields according to the mitral bioprostheses positioning. Also, changes in the aortic upstream velocity profiles were noticed as a function of mitral orientations.     

Investigation of Ethylene Oxide-co-propylene Oxide for Dissolution Enhancement of Hot-Melt Extruded Solid Dispersions

The optimal design of amorphous solid dispersion formulations requires the use of excipients to maintain supersaturation and improve physical stability to ensure shelf-life stability and better absorption during intestinal transit, respectively. Blends of excipients (surfactants and polymers) are often used within pharmaceutical products to improve the oral delivery of Biopharmaceutical Classification System class II drugs. Therefore, in this study, a dissolution enhancer, poloxamer 407 (P407), was investigated to determine its effect on the dissolution properties and on the amorphous nature of the active pharmaceutical ingredient contained in the formulation. Phase solubility studies of indomethacin (INM) in aqueous solutions of P407 and poly(vinylpyrrolidone-vinyl acetate copolymer) showed an increase in the kinetic solubility of INM compared with the pure drug at 37°C with a K_a value of 0.041 μg/mL. The solid dispersions showed a higher dissolution rate when compared to pure and amorphous drugs when performed in pH buffer 1.2 with a kinetic solubility of 21 μg/mL. The stability data showed that the amorphous drug in solid solutions with poly(vinylpyrrolidone-vinyl acetate copolymer) and P407 remained amorphous, and the %P407 loading had no effect on the amorphous stability of INM. This study concluded that the amorphous solid dispersion contributed to the increased solubility of INM.     

Measurement of Average Aggregate Density by Sedimentation and Brownian Motion Analysis

The spatially averaged density of protein aggregates is an important parameter that can be used to relate size distributions measured by orthogonal methods, to characterize protein particles, and perhaps to estimate the amount of protein in aggregate form in a sample. We obtained a series of images of protein aggregates exhibiting Brownian diffusion while settling under the influence of gravity in a sealed capillary. The aggregates were formed by stir-stressing a monoclonal antibody (NISTmAb). Image processing yielded particle tracks, which were then examined to determine settling velocity and hydrodynamic diameter down to 1 μm based on mean square displacement analysis. Measurements on polystyrene calibration microspheres ranging in size from 1 to 5 μm showed that the mean square displacement diameter had improved accuracy over the diameter derived from imaged particle area, suggesting a future method for correcting size distributions based on imaging. Stokes' law was used to estimate the density of each particle. It was found that the aggregates were highly porous with density decreasing from 1.080 to 1.028 g/cm³ as the size increased from 1.37 to 4.9 μm.     

Process Development and Robust Control of Physical Attributes of an Amorphous Drug Substance

Control of physical attributes of amorphous active pharmaceutical ingredients (APIs) can be challenging due to processability issues, their wide variation during processing and the requirement to control them to specific ranges. In this article, we report our efforts to develop a robust isolation process for boceprevir, which delivers specific surface areas between 3.0 and 9.4 m²/g. We developed mechanistic process understanding by utilizing a new method to measure glass transition temperature of API suspensions. Boceprevir processability and surface area are determined by the interplay between the suspension operating conditions and glass transition temperature. Processing time and thermal history also influence API surface area evolution, rendering a dynamic nature to it. A control strategy was developed consisting of 2 elements: a continuous tee mixer precipitation process, which delivers API in the 40-60 m²/g range and 1 of 2 annealing step variants. In the first, surface area was controlled in 4 batches to 6.7-7.5 m²/g by equilibrating the API suspension above its glass transition temperature and a subsequent vacuum distillation. The second annealing variant controlled surface area to 4.5-6.5 m²/g for over 70 commercial batches through a dynamic vacuum distillation step with prescribed temperature and % batch volume distilled profiles versus time.     

Physical and Biochemical Characterization of Chemically Treated Pollen Shells for Potential Use in Oral Delivery of Therapeutics

Allergen-free pollen shells obtained from natural pollen grains have recently attracted attention as microcapsules for oral therapeutic delivery. We have recently developed a chemical treatment method that enables successful retrieval of hollow pollen shells from diverse species. A comprehensive characterization is critical to characterize the effects of chemical treatment which will not only benchmark the pollen treatment process but can also lay the foundation of quality control procedures to check allergen-removal efficiency during pollen treatment. Therefore, in this study, we followed the effects of chemical treatment on 4 different pollen species using electron microscopy, elemental analysis, gel electrophoresis, confocal microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. These analyses revealed that acetone treatment removed lipids from the pollen surface. Phosphoric acid treatment removed proteins and nucleic acids from the pollen core and transformed esters into carboxylic acids. Potassium hydroxide hydrolysis changed carbohydrate composition of the pollen wall. Chemically treated pollen shells exhibited hydroxyl and carboxyl functional groups on their surface. Overall, we propose that confocal microscopy could be used as a rapid scanning technique to visualize the removal of biomolecules, whereas Fourier-transform infrared combined with gel electrophoresis could be used as a more objective approach for analysis and benchmarking.     

(S)-N-环氧丙基邻苯二甲酰亚胺的单晶制备及其表征

目的制备(S)-N-环氧丙基邻苯二甲酰亚胺的单晶,并对其进行结构表征和均浆稳定性研究。方法通过溶剂挥发法和气相扩散法制备(S)-N-环氧丙基邻苯二甲酰亚胺晶型。利用差示扫描量热仪(DSC)、热重分析仪(TGA),红外光谱仪(IR),粉末X射线衍射仪(PXRD)和单晶X射线衍射仪(SXRD)分别对制备得到的晶体样品进行表征。结果制备得到的(S)-N-环氧丙基邻苯二甲酰亚胺晶体样品,其DSC、TGA、IR和PXRD图谱均一致,即晶型一致;DSC结合TGA分析结果显示,(S)-N-环氧丙基邻苯二甲酰亚胺熔点为100.56℃,分解温度为128.2℃。单晶X射线衍射结果表明该晶胞属于单斜晶系,P2_1空间群,结构偏离因子R=0.04,分子式为C_(11)H_9NO_3,相对分子质量为203.19,立体构型与预测构型一致。均浆稳定性实验结果表明,不同极性溶剂中得到的晶体粉末X射线未发生变化,即晶型稳定性良好。结论实验确证了(S)-N-环氧丙基邻苯二甲酰亚胺的立体结构,且晶型稳定性良好。