Recent years have seen an increase of extracellular vesicle (EV) research geared towards biological understanding, diagnostics and therapy. However, EV data interpretation remains challenging owing to complexity of biofluids and technical variation introduced during sample preparation and analysis. To understand and mitigate these limitations, we generated trackable recombinant EV (rEV) as a biological reference material. Employing complementary characterization methods, we demonstrate that rEV are stable and bear physical and biochemical traits characteristic of sample EV. Furthermore, rEV can be quantified using fluorescence-, RNA- and protein-based technologies available in routine laboratories. Spiking rEV in biofluids allows recovery efficiencies of commonly implemented EV separation methods to be identified, intra-method and inter-user variability induced by sample handling to be defined, and to normalize and improve sensitivity of EV enumerations. We anticipate that rEV will aid EV-based sample preparation and analysis, data normalization, method development and instrument calibration in various research and biomedical applications.

The crystallization of metastable crystal polymorphs in polymer matrices has been extensively reported in literature as a possible approach to enhance the solubility of poorly water-soluble drug compounds, yet no clarification of the mechanism of the polymorph formation has been proposed. The current work aims to elucidate the polymorphism behavior of the model compound indomethacin as well as the mechanism of polymorph selection of drugs in semicrystalline systems. Indomethacin crystallized as either the α- or τ-form, a new metastable form, or a mixture of the two polymorphs in dispersions containing different drug loadings in polyethylene glycol, poloxamer, or Gelucire as the result of the variation in the mobility of drug molecules. As a general rule, low molecular mobility of the amorphous drug favors the crystallization into thermodynamically stable forms whereas metastable crystalline polymorphs are preferred when the molecular mobility of the drug is sufficiently high. This rule provides insight into the polymorph selection of numerous active pharmaceutical ingredients in semicrystalline dispersions and can be used as a guide for polymorphic screening from melt crystallization by tuning the mobility of drug molecules. In addition, the drug crystallized faster while the polymer crystallized slower as the drug-loading increased with the maxima of drug crystallization rate in 70% indomethacin dispersion. Increasing the drug content in solid dispersions reduced the τ to α polymorphic transition rate, except for when the more stable form was initially dominant. The segregation of τ and α polymorphs as well as the polymorphic transformation during storage led to the inherent inhomogeneity of the semicrystalline dispersions. This study highlights and expands our understanding about the complex crystallization behavior of semicrystalline systems and is crucial for preparation of solid dispersions with reproducible and consistent physicochemical properties and pharmaceutical performance.

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ABSTRACT:16 17Spin-freezing as alternative freezing approach was evaluated as part of an innovative 18 continuous pharmaceutical freeze-drying concept for unit doses. The aim of this paper 19 was to compare the sublimation rate of spin-frozen vials versus traditionally frozen vials 20 in a batch freeze-dryer, and its impact on total drying time. 21Five different formulations, each having a different dry cake resistance, were tested. 23After freezing, the traditionally frozen vials were placed on the shelves while the spin-24 frozen vials were placed in aluminium vial holders providing radial energy supply during 25 drying. Different primary drying conditions and chamber pressures were evaluated. 26After two hours of primary drying, the amount of sublimed ice was determined in each 27 vial. Each formulation was monitored in-line using NIR spectroscopy during drying to

Traditional pharmaceutical freeze-drying is an inefficient batch process often applied to improve the stability of biopharmaceutical drug products. The freeze-drying process is regulated by the (dynamic) settings of the adaptable process parameters shelf temperature T and chamber pressure P. Mechanistic modelling of the primary drying step allows the computation of the optimal combination of T and P in function of the primary drying time. In this study, an uncertainty analysis was performed on the mechanistic primary drying model to construct the dynamic Design Space for the primary drying step of a freeze-drying process, allowing to quantitatively estimate and control the risk of cake collapse (i.e., the Risk of Failure (RoF)). The propagation of the error on the estimation of the thickness of the dried layer L as function of primary drying time was included in the uncertainty analysis. The constructed dynamic Design Space and the predicted primary drying endpoint were experimentally verified for different RoF acceptance levels (1%, 25%, 50% and 99% RoF), defined as the chance of macroscopic cake collapse in one or more vials. An acceptable cake structure was only obtained for the verification runs with a preset RoF of 1% and 25%. The run with the nominal values for the input variables (RoF of 50%) led to collapse in a significant number of vials. For each RoF acceptance level, the experimentally determined primary drying endpoint was situated below the computed endpoint, with a certainty of 99%, ensuring sublimation was finished before secondary drying was started. The uncertainty on the model input parameters demonstrates the need of the uncertainty analysis for the determination of the dynamic Design Space to quantitatively estimate the risk of batch rejection due to cake collapse.