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Publikation Evaluation of gravitational consolidation of binary powder mixtures by modified Heckel equation(Elsevier, 2022) Svačinová, Petra; Macho, Oliver; Jarolímová, Žofie; Gabrišová, Ľudmila; Šklubalová, Zdenka; Kuentz, MartinConsolidation of powders by tapping is an important quality test but it is time and material consuming, which encourages the use of mathematical modelling. This article aims to study this gravitational consolidation dynamics by using nine binary mixtures consisting of cellets and powdered microcrystalline cellulose (MCC102), differing in size, shape, and consolidation properties. To describe the correlation between number of taps and powder bed density/ porosity, the modified Heckel equation. (MH) was newly introduced and compared to the models by Kawakita (KW) and Varthalis & Pilpel (VP). High coefficients of determination were observed by applying the traditional KW model up to 80% of cellets, while a comparable fitting adequacy was obtained with the MH equation up to 50% of cellets in the mixtures. An increased content of MCC102 increased fitting adequacy in the MH and KW model, whereas a nearly opposite mixture trend was observed for the VP model.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Hydroxypropyl Cellulose for Drug Precipitation Inhibition: From the Potential of Molecular Interactions to Performance Considering Microrheology(American Chemical Society, 10.01.2022) Stoyanov, Edmont; Niederquell, Andreas; Kuentz, MartinThere has been recent interest in using hydroxypropyl cellulose (HPC) for supersaturating drug formulations. This study investigated the potential for molecular HPC interactions with the model drug celecoxib by integrating novel approaches in the field of drug supersaturation analysis. Following an initial polymer characterization study, quantum-chemical calculations and molecular dynamics simulations were complemented with results of inverse gas chromatography and broadband diffusing wave spectroscopy. HPC performance was studied regarding drug solubilization and kinetics of desupersaturation using different grades (i.e., HPC-UL, SSL, SL, and L). The results suggested that the potential contribution of dispersive interactions and hydrogen bonding depended strongly on the absence or presence of the aqueous phase. It was proposed that aggregation of HPC polymer chains provided a complex heterogeneity of molecular environments with more or less excluded water for drug interaction. In precipitation experiments at a low aqueous polymer concentration (i.e., 0.01%, w/w), grades L and SL appeared to sustain drug supersaturation better than SSL and UL. However, UL was particularly effective in drug solubilization at pH 6.8. Thus, a better understanding of drug–polymer interactions is important for formulation development, and polymer blends may be used to harness the combined advantages of individual polymer grades.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Advancing Raman model calibration for perfusion bioprocesses using spiked harvest libraries(Wiley, 07.08.2022) Kolar, Jakub; Herwig, Christoph; Bielser, Jean‐Marc; Romann, Patrick; Tobler, Daniela; Villiger, ThomasBackground Raman spectroscopy has gained popularity to monitor multiple process indicators simultaneously in biopharmaceutical processes. However, robust and specific model calibration remains a challenge due to insufficient analyte variability to train the models and high cross-correlation of various media components and artifacts throughout the process. Main Methods A systematic Raman calibration workflow for perfusion processes enabling highly specific and fast model calibration was developed. Harvest libraries consisting of frozen harvest samples from multiple CHO cell culture bioreactors collected at different process times were established. Model calibration was subsequently performed in an offline setup using a flow cell by spiking process harvest with glucose, raffinose, galactose, mannose, and fructose. Major Results In a screening phase, Raman spectroscopy was proven capable not only to distinguish sugars with similar chemical structures in perfusion harvest but also to quantify them independently in process-relevant concentrations. In a second phase, a robust and highly specific calibration model for simultaneous glucose (root mean square error prediction [RMSEP] = 0.32 g L−1) and raffinose (RMSEP = 0.17 g L−1) real-time monitoring was generated and verified in a third phase during a perfusion process. Implication The proposed novel offline calibration workflow allowed proper Raman peak decoupling, reduced calibration time from months down to days, and can be applied to other analytes of interest including lactate, ammonia, amino acids, or product titer. Graphical Abstract and Lay Summary Building accurate and robust Raman models for online monitoring of cell culture processes remains a difficult and time-consuming process, particularly for perfusion processes. In this study, the authors developed a novel offline calibration approach based on design-of-experiment spiking and a harvesting library. The Raman spectra of these spiked harvest samples allowed proper peak decoupling and model generation within days instead of weeks or even months. The approach has been successfully applied to monitor various sugars in perfusion bioreactors and other compounds as well as process modes may equally benefit from the described workflow.01A - Beitrag in wissenschaftlicher Zeitschrift