Romann, Patrick
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Development of a unique rapid test to detect anti-bodies directed against an extended RBD of SARS-CoV-2 spike protein
Serological testing for antibodies directed against SARS-CoV-2 in patients may serve as a diagnostic tool to verify a previous infection and as surrogate for an elicited humoral immune response, ideally conferring immunity after infection or vaccination. Here, we present the recombinant expression of an extended receptor binding domain (RBD) of the SARS-CoV-2 Spike protein used as capture antigen in a unique rapid immunoassay to detect the presence of RBD binding antibodies with high sensitivity and specificity. As currently available vaccines focus on the Spike RBD as target, the developed test can also be used to monitor a successful immune response after vaccination with an RBD based vaccine.
Co‐current filtrate flow in TFF perfusion processes. Decoupling transmembrane pressure from crossflow to improve product sieving
Hollow fiber‐based membrane filtration has emerged as the dominant technology for cell retention in perfusion processes yet significant challenges in alleviating filter fouling remain unsolved. In this work, the benefits of co‐current filtrate flow applied to a tangential flow filtration (TFF) module to reduce or even completely remove Starling recirculation caused by the axial pressure drop within the module was studied by pressure characterization experiments and perfusion cell culture runs. Additionally, a novel concept to achieve alternating Starling flow within unidirectional TFF was investigated. Pressure profiles demonstrated that precise flow control can be achieved with both lab‐scale and manufacturing‐scale filters. TFF systems with co‐current flow showed up to 40% higher product sieving compared to standard TFF. The decoupling of transmembrane pressure from crossflow velocity and filter characteristics in co‐current TFF alleviates common challenges for hollow fiber‐based systems such as limited crossflow rates and relatively short filter module lengths, both of which are currently used to avoid extensive pressure drop along the filtration module. Therefore, co‐current filtrate flow in unidirectional TFF systems represents an interesting and scalable alternative to standard TFF or alternating TFF operation with additional possibilities to control Starling recirculation flow.
Advancing Raman model calibration for perfusion bioprocesses using spiked harvest libraries
Background 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.