Publications by authors named "Dörte Sölle"

16 Publications

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Monitoring cell productivity for the production of recombinant proteins by flow cytometry: An effective application using the cold capture assay.

Eng Life Sci 2021 May 6;21(5):288-293. Epub 2021 Jan 6.

Institute of Technical Chemistry Leibniz University Hannover Hannover Germany.

Due to the increasing economic and social relevance of biotherapeutics, their production processes are continually being reconsidered and reoptimized in an effort to secure higher product concentrations and qualities. Monitoring the productivity of cultured cells is therefore a critically important part of the cultivation process. Traditionally, this is achieved by determining the overall product titer by high performance liquid chromatography (HPLC), and then calculating the specific cell productivity based on this titer and an associated viable cell density. Unfortunately, this process is typically time-consuming and laborious. In this study, the productivity of Chinese Hamster Ovary (CHO) cells expressing a monoclonal antibody was analyzed over the course of the cultivation process. In addition to calculating the specific cell productivity based on the traditional product titer determined by HPLC analysis, culture productivity of single cells was also analyzed via flow cytometry using a cold capture assay. The cold capture assay is a cell surface labelling technique described by Brezinsky et al., which allows for the visualization of a product on the surface of the producing cell. The cell productivity results obtained via HPLC and the results of cold capture assay remained in great accordance over the whole cultivation process. Accordingly, our study demonstrates that the cold capture assay offers an interesting, comparatively time-effective, and potentially cheaper alternative for monitoring the productivity of a cell culture.
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http://dx.doi.org/10.1002/elsc.202000049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8092981PMC
May 2021

Implementation of QbD strategies in the inoculum expansion of a mAb production process.

Eng Life Sci 2021 Mar 3;21(3-4):196-207. Epub 2020 Dec 3.

Leibniz Universität Hannover Institut für Technische Chemie Hannover Germany.

The quality by design approach was introduced to the biopharmaceutical industry over 15 years ago. This principle is widely implemented in the characterization of monoclonal antibody production processes. Anyway, the early process phase, namely the inoculum expansion, was not yet investigated and characterized for most processes. In order to increase the understanding of early process parameter interactions and their influence on the later production process, a risk assessment followed by a design of experiments approach was conducted. The DoE included the critical parameters methotrexate (MTX) concentration, initial passage viable cell density and passage duration. Multivariate data analysis led to mathematical regression models and the establishment of a designated design space for the studied parameters. It was found that the passage duration as well as the initial viable cell density for each passage during the inoculum expansion have severe effects on the growth rate and viability of the early process phase. Furthermore, the variations during the inoculum expansion directly influenced the production process responses. This carry-over of factor effects highlights the crucial impact of early process failures and the importance of process analysis and control during the first part of mAb production processes.
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http://dx.doi.org/10.1002/elsc.202000056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7923587PMC
March 2021

Development and characterization of a fiber optical fluorescence sensor for the online monitoring of biofilms and their microenvironment.

Eng Life Sci 2020 Jul 2;20(7):252-264. Epub 2020 Mar 2.

Institute of Technical Chemistry Leibniz University Hannover Hannover Germany.

The growth of microorganisms on surfaces and interfaces as a biofilm is very common and plays important role in various areas such as material science, biomedicine, or waste treatment among others. Due to their inhomogeneous structure and the variance in the microorganism consortium, the analysis of biofilms represents a significant challenge. An online fluorescence sensor was developed that is able to measure the most important biological fluorophores (proteins, nicotinamide adenine dinucleotide, and flavin) in a noninvasive manner in biofilms, e.g. in bioelectrochemical applications. The sensor gives the opportunity to continuously draw conclusions on the metabolic state of the biofilm. The developed sensor has a diameter of 1 mm at the sensor tip and can be moved on and into the biofilm surface. In the first experiment, the measuring range of the sensor and the long-term stability could be determined and the system applicability was confirmed. In addition, measurements in biofilm-like structures could be performed. The formation of a wastewater-based biofilm was monitored using the developed sensor, demonstrating the functionality of the sensor in a proof-of-principle experiment.
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http://dx.doi.org/10.1002/elsc.201900140DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7336156PMC
July 2020

High cell density transient transfection of CHO cells for TGF-β1 expression.

Eng Life Sci 2019 Nov 2;19(11):730-740. Epub 2019 Sep 2.

Institute of Technical Chemistry Gottfried Wilhelm Leibniz University of Hannover Hannover Germany.

High cell densities for transient transfection with polyethyleneimine (PEI) can be used for rapid and maximal production of recombinant proteins. High cell densities can be obtained by different cultivation systems, such as batch or perfusion systems. Herein, densities up to 18 million cells/mL were obtained by centrifugation for transfection evaluation. PEI transfection efficiency was easily determined by transfected enhanced green fluorescence protein (EGFP) reporter plasmid DNA (pDNA). A linear correlation between fluorescence intensity and transfection efficiency was improved. The transfection efficiency of PEI was highly dependent on the transfection conditions and directly related to the level of recombinant protein. Several factors were required to optimize the transient transfection process; these factors included the media type (which is compatible with low or high cell density transfection), the preculture CHO-K1 suspension cell density, and the pDNA to PEI level. Based on design of experiment (DoE) analyses, the optimal transfection conditions for 10 × 10 cells/mL in the CHOMACS CD medium achieved 73% transfection efficiency and a cell viability of over 80%. These results were confirmed for the production of transforming growth factor-beta 1 (TGF-β1) in a shake flask. The purified TGF-β1 protein concentration from 60 mL supernatant was 27 µg/mL, and the protein was biologically active.
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http://dx.doi.org/10.1002/elsc.201800174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999575PMC
November 2019

Process Optimization using High Throughput Automated Micro-Bioreactors in Chinese Hamster Ovary Cell Cultivation.

J Vis Exp 2020 05 18(159). Epub 2020 May 18.

Institute for Technical Chemistry, Gottfried-Wilhelm-Leibniz Universität Hannover.

Optimization of bioprocesses to increase the yield of desired products is of importance in the biopharmaceutical industry. This can be achieved by strain selection and by developing bioprocess parameters. Shake flasks have been used for this purpose. They, however, lack the capability to control the process parameters such as pH and dissolved oxygen (DO). This limitation can be overcome with the help of an automated micro-bioreactor. These bioreactors mimic cultivation at a larger scale. One of the major advantages of this system is the integration of the Design of Experiment (DOE) in the software. This integration enables establishing a design where multiple process parameters can be varied simultaneously. The critical process parameters and optimum bioprocess conditions can be analyzed within the software. The focus of the work presented here is to introduce the user to the steps involved in process design in the software and incorporation of the DOE within the cultivation run.
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http://dx.doi.org/10.3791/60577DOI Listing
May 2020

Be FAIR to your data.

Authors:
Dörte Solle

Anal Bioanal Chem 2020 Jul 16;412(17):3961-3965. Epub 2020 Apr 16.

Leibniz Universität Hannover, Callinstr.5, 30167, Hannover, Germany.

Wouldn't it be great, if experimental data were findable wherever they were? If experimental data were accessible' regardless of the storage place and format? If experimental data were interoperable independent of the author or its origin? If experimental data were reusable for further analysis without experimental repetition? The current state of the art of data acquisition in the laboratory is very diverse. A lot of different devices are used, analogue as well as digital ones. Usually all experimental setups and observations are summarized in a handwritten lab notebook, independently from digital or analogue sources. To change the actual and common way of laboratory data acquisition into a digital and modern one, electronic lab notebooks can be used. A challenge of science is to facilitate knowledge discovery by assisting humans and machines in their discovery of scientific data and their associated algorithms and workflows. FAIR describes a set of guiding principles to make data Findable, Accessible, Interoperable, and Reusable.
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http://dx.doi.org/10.1007/s00216-020-02526-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7320032PMC
July 2020

Online monitoring of the cell-specific oxygen uptake rate with an in situ combi-sensor.

Anal Bioanal Chem 2020 Apr 4;412(9):2111-2121. Epub 2019 Dec 4.

Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany.

In a biotechnological process, standard monitored process variables are pH, partial oxygen pressure (pO), and temperature. These process variables are important, but they do not give any information about the metabolic activity of the cell. The ISICOM is an in situ combi-sensor that is measuring the cell-specific oxygen uptake rate (qOUR) online. This variable allows a qualitative judgement of metabolic cell activity. The measuring principle of the ISICOM is based on a volume element enclosed into a small measuring chamber. Inside the measuring chamber, the pO and the scattered light is measured. Within a defined measuring interval, the chamber closes, and the oxygen supply for the cells is interrupted. The decreasing oxygen concentration is recorded by the pO optode. This measuring principle, known as the dynamic method, determines the oxygen uptake rate (OUR). Together with the scattered light signal, the cell concentration is estimated and the qOUR is available online. The design of the ISICOM is focused on functionality, sterility, long-term stability, and response time behavior so the sensor can be used in bioprocesses. With the ISICOM, measurement of online and in situ measurement of the OUR is possible. The OUR and qOUR online measurement of an animal cell batch cultivation is demonstrated, with maximum values of OUR = 2.5 mmol L h and a qOUR = 9.5 pmol cell day. Information about limitation of the primary and secondary substrate is derived by the monitoring of the metabolic cell activity of bacteria and yeast cultivation processes. This sensor contributes to a higher process understanding by offering an online view on to the cell behavior. In the sense of process analytical technology (PAT), this important information is needed for bioprocesses to realize a knowledge base process control.
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http://dx.doi.org/10.1007/s00216-019-02260-9DOI Listing
April 2020

Membrane Adsorber for the Fast Purification of a Monoclonal Antibody Using Protein A Chromatography.

Membranes (Basel) 2019 Nov 27;9(12). Epub 2019 Nov 27.

Institute of Technical Chemistry, Callinstraße 5, 30167 Hannover, Germany.

Monoclonal antibodies are conquering the biopharmaceutical market because they can be used to treat a variety of diseases. Therefore, it is very important to establish robust and optimized processes for their production. In this article, the first step of chromatography (Protein A chromatography) in monoclonal antibody purification was optimized with a focus on the critical elution step. Therefore, different buffers (citrate, glycine, acetate) were tested for chromatographic performance and product quality. Membrane chromatography was evaluated because it promises high throughputs and short cycle times. The membrane adsorber Sartobind Protein A 2 mL was used to accelerate the purification procedure and was further used to perform a continuous chromatographic run with a four-membrane adsorber-periodic counter-current chromatography (4MA-PCCC) system. It was found that citrate buffer at pH 3.5 and 0.15 M NaCl enabled the highest recovery of >95% and lowest total aggregate content of 0.26%. In the continuous process, the capacity utilization of the membrane adsorber was increased by 20%.
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http://dx.doi.org/10.3390/membranes9120159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950724PMC
November 2019

A novel LED-based 2D-fluorescence spectroscopy system for in-line monitoring of Chinese hamster ovary cell cultivations - Part I.

Eng Life Sci 2019 May 7;19(5):352-362. Epub 2019 Apr 7.

R&D Spectroscopy & Chemometrics Sartorius Stedim Biotech GmbH Göttingen Germany.

A new two-dimensional fluorescence sensor system was developed for in-line monitoring of mammalian cell cultures. Fluorescence spectroscopy allows for the detection and quantification of naturally occurring intra- and extracellular fluorophores in the cell broth. The fluorescence signals correlate to the cells' current redox state and other relevant process parameters. Cell culture pretests with twelve different excitation wavelengths showed that only three wavelengths account for a vast majority of spectral variation. Accordingly, the newly developed device utilizes three high-power LEDs as excitation sources in combination with a back-thinned CCD-spectrometer for fluorescence detection. This setup was first tested in a lab design of experiments study with process relevant fluorophores proving its suitability for cell culture monitoring with LOD in the μg/L range. The sensor was then integrated into a CHO-K1 cell culture process. The acquired fluorescence spectra of several batches were evaluated using multivariate methods. The resulting batch evolution models were challenged in deviating and "golden batch" validation runs. These first tests showed that the new sensor can trace the cells' metabolic state in a fast and reliable manner. Cellular distress is quickly detected as a deviation from the "golden batch".
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http://dx.doi.org/10.1002/elsc.201800149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999564PMC
May 2019

A novel LED-based 2D-fluorescence spectroscopy system for in-line bioprocess monitoring of Chinese hamster ovary cell cultivations-Part II.

Eng Life Sci 2019 May 14;19(5):341-351. Epub 2019 Mar 14.

Institute of Technical Chemistry Gottfried Wilhelm Leibniz University of Hannover Hannover Germany.

This study was performed in order to evaluate a new LED-based 2D-fluorescence spectrometer for in-line bioprocess monitoring of Chinese hamster ovary (CHO) cell culture processes. The new spectrometer used selected excitation wavelengths of 280, 365, and 455 nm to collect spectral data from six 10-L fed-batch processes. The technique provides data on various fluorescent compounds from the cultivation medium as well as from cell metabolism. In addition, scattered light offers information about the cultivation status. Multivariate data analysis tools were applied to analyze the large data sets of the collected fluorescence spectra. First, principal component analysis was used to accomplish an overview of all spectral data from all six CHO cultivations. Partial least square regression models were developed to correlate 2D-fluorescence spectral data with selected critical process variables as offline reference values. A separate independent fed-batch process was used for model validation and prediction. An almost continuous in-line bioprocess monitoring was realized because 2D-fluorescence spectra were collected every 10 min during the whole cultivation. The new 2D-fluorescence device demonstrates the significant potential for accurate prediction of the total cell count, viable cell count, and the cell viability. The results strongly indicated that the technique is particularly capable to distinguish between different cell statuses inside the bioreactor. In addition, spectral data provided information about the lactate metabolism shift and cellular respiration during the cultivation process. Overall, the 2D-fluorescence device is a highly sensitive tool for process analytical technology applications in mammalian cell cultures.
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http://dx.doi.org/10.1002/elsc.201800146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999457PMC
May 2019

Sensors for disposable bioreactors.

Eng Life Sci 2017 Aug 28;17(8):940-952. Epub 2017 Aug 28.

Institute of Technical Chemistry Leibniz University Hannover Germany.

Modern bioprocess monitoring demands sensors that provide on-line information about the process state. In particular, sensors for monitoring bioprocesses carried out in single-use bioreactors are needed because disposable systems are becoming increasingly important for biotechnological applications. Requirements for the sensors used in these single-use bioreactors are different than those used in classical reusable bioreactors. For example, long lifetime or resistance to steam and cleaning procedures are less crucial factors, while a requirement of sensors for disposable bioreactors is a cost that is reasonable on a per-use basis. Here, we present an overview of current and emerging sensors for single-use bioreactors, organized by the type of interface of the sensor systems to the bioreactor. A major focus is on non-invasive, in-situ sensors that are based on electromagnetic, semiconducting, optical, or ultrasonic measurements. In addition, new technologies like radio-frequency identification sensors or free-floating sensor spheres are presented. Notably, at this time there is no standard interface between single-use bioreactors and the sensors discussed here. In the future, manufacturers should address this shortcoming to promote single-use bioprocess monitoring and control.
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http://dx.doi.org/10.1002/elsc.201700049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999375PMC
August 2017

Spectroscopic sensors for in-line bioprocess monitoring in research and pharmaceutical industrial application.

Anal Bioanal Chem 2017 Jan 30;409(3):651-666. Epub 2016 Nov 30.

Institute of Technical Chemistry, Gottfried Wilhelm Leibniz University of Hannover, Callinstraße 5, 30167, Hannover, Germany.

The use of spectroscopic sensors for bioprocess monitoring is a powerful tool within the process analytical technology (PAT) initiative of the US Food and Drug Administration. Spectroscopic sensors enable the simultaneous real-time bioprocess monitoring of various critical process parameters including biological, chemical, and physical variables during the entire biotechnological production process. This potential can be realized through the combination of spectroscopic measurements (UV/Vis spectroscopy, IR spectroscopy, fluorescence spectroscopy, and Raman spectroscopy) with multivariate data analysis to obtain relevant process information out of an enormous amount of data. This review summarizes the newest results from science and industry after the establishment of the PAT initiative and gives a critical overview of the most common in-line spectroscopic techniques. Examples are provided of the wide range of possible applications in upstream processing and downstream processing of spectroscopic sensors for real-time monitoring to optimize productivity and ensure product quality in the pharmaceutical industry.
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http://dx.doi.org/10.1007/s00216-016-0068-xDOI Listing
January 2017

Chemometric modeling and two-dimensional fluorescence analysis of bioprocess with a new strain of Klebsiella pneumoniae to convert residual glycerol into 1,3-propanediol.

J Ind Microbiol Biotechnol 2012 May 18;39(5):701-8. Epub 2012 Jan 18.

Biotechnology & Biochemical Engineering Laboratory-BiotecLab, Federal University of Rio Grande do Sul, Av. Bento Gonçalves, 9500, P.O. Box 15090, Porto Alegre, RS 91501-970, Brazil.

The goal of this study was to show that the metabolism of Klebsiella pneumoniae under different aeration strategies could be monitored and predicted by the application of chemometric models and fluorescence spectroscopy. Multi-wavelength fluorescence was applied to the on-line monitoring of process parameters for K. pneumoniae cultivations. Differences observed in spectra collected under aerobiosis and anaerobiosis can be explained by the different metabolic states of the cells. To predict process variables such as biomass, glycerol, and 1,3-propanediol (1,3-PD), chemometric models were developed on the basis of the acquired fluorescence spectra, which were measured continuously. Although glycerol and 1,3-PD are not fluorescent compounds, the results showed that this technique could be successfully applied to the on-line monitoring of variables in order to understand the process and thus improve 1,3-PD production. The root mean square errors of predictions were 0.78 units, 10 g/L, and 2.6 g/L for optical density, glycerol, and 1,3-PD, respectively.
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http://dx.doi.org/10.1007/s10295-011-1075-8DOI Listing
May 2012

Transcriptomics does not show adverse effects of beta-carotene in A/J mice exposed to smoke for 2 weeks.

Arch Biochem Biophys 2007 Sep 18;465(2):336-46. Epub 2007 Jul 18.

DSM Nutritional Products, Human Nutrition and Health, PO Box 3255, Building 241/421, CH-4002 Basel, Switzerland.

Beta-carotene (betaC) supplementation in smokers was unexpectedly associated with increased incidence of lung cancer versus smoking alone. We performed a study in A/J mice to explore possible betaC/cigarette smoke (CS) interactions potentially influencing lung cancer risk in smokers. A/J mice received a diet containing 120 or 600 ppm betaC for six weeks, and exposed to mainstream CS (140 mg total suspended particulates/m(3)) during the last two weeks. Lung transcriptomics analysis revealed that CS induced drug metabolism, oxidative stress, extracellular matrix (ECM) degradation, inflammation markers, and apoptosis. betaC reduced CS-induced inflammation markers and ECM degradation. betaC modulated the CS effect on apoptosis without a clear pro- or anti-apoptotic trend. betaC alone induced only minor changes of gene expression. In conclusion, betaC/CS interactions caused gene regulations in lungs. CS was the main effector. The gene regulations overall did not indicate that betaC exacerbated CS effects. Dose-dependency of betaC effects was minor and not detectable by genome-wide data mining.
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http://dx.doi.org/10.1016/j.abb.2007.06.034DOI Listing
September 2007

Chemometric modelling with two-dimensional fluorescence data for Claviceps purpurea bioprocess characterization.

J Biotechnol 2003 Oct;105(1-2):179-88

Institut für Technische Chemie, Universität Hannover, Callinstr 3, 30167 Hannover, Germany.

Modern bioprocess control requires fast data acquisition and in-time evaluation of bioprocess variables. On-line fluorescence spectroscopy and the application of chemometric methods accomplish these goals. In order to demonstrate how time-consuming off-line analysis methods can be replaced for bioprocess monitoring, fluorescence measurements were performed during different cultivations of the fungus Claviceps purpurea. To predict process variables like biomass, protein, and alkaloid concentrations, chemometric models were developed on the basis of the acquired fluorescence spectra. The results of these investigations are presented and the applicability of this approach for bioprocess monitoring is discussed.
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http://dx.doi.org/10.1016/s0168-1656(03)00189-5DOI Listing
October 2003