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Biomedical subjects

U Bilitewski

Publications and source records attributed to U Bilitewski.

23 records · Page 2Linked to original sources
PubMed1994

On-line monitoring of monoclonal antibody production with regenerable flow-injection immuno systems.

In this paper two systems for the observation of the production of mouse-IgG during the cultivation of hybridoma cells in a perfusion reactor are presented. The direct immunosystem is based on the detection of changes in capacitance of a dielectric layer (tantalum oxide) on a metal surface (tantalum) when antibodies bind to immobilized anti-antibodies. The sensor consisted of a 25 nm tantalum oxide layer, electrochemically grown onto a laser patternized 1 micron thick tantalum layer. The indirect system is based on an automated fluorimetric sandwich ELISA system with beta-galactosidase conjugated secondary antibodies. Two cultivations of mouse hybridoma cells in a 2-1 perfusion reactor were performed. The first cultivation was monitored with the capacitance system, the second cultivation was monitored with the fluorimetric system.

Animals↗
PubMed1993

Comparison of different biosensor systems suitable for bioprocess monitoring.

To achieve effective bioprocess monitoring, sensing systems are required which are suitable for an on-line determination of substrates, inhibitors, nutrients or products. Such devices may utilise biochemical principles, i.e. the specific interaction of biochemical receptors with their surroundings. They can be constructed either as in situ sensors or as flow-through sensors connected to the process via sampling devices. Hence, characteristic features of an in situ glucose electrode are described, e.g. analytical range, sensitivity and stability. The sensor was based on mediated electron transfer from the enzyme glucose oxidase to the graphite electrode, the mediators being tetrathiafulvalene (TTF) or dimethylferrocene (DMF). Additionally, various flow injection analysis (FIA) systems based on oxidases, which were immobilised either on controlled pore glass or in a membrane, were characterised with respect to analytical ranges and sensitivities and applied to glucose, lactate and glutamate determinations in off-line samples taken from an animal cell cultivation.

Biosensing Techniques↗
PubMed1993

Control of microbial activity by flow injection analysis during high cell density cultivation of Escherichia coli.

The application of an automated flow injection analysis (FIA) system for on-line determination of microbial activity, during high cell density cultivations of Escherichia coli is reported. Based on a bioelectrochemical principle, the FIA method used a redox mediator (potassium hexacyanoferrate(III)) to facilitate electron transfer from the microorganisms to an electrochemical detector. Assays were carried out using a new sampling device which provided aseptic operation by use of a valve and chemical sterilisation. No sample dilution or pretreatment was necessary for biomass concentrations up to approx. 40 g l-1. The sample volume was 0.5 ml and the overall analysis time was 5 min. FIA signals were found to correlate well with the oxygen uptake rate (OUR). Changes in metabolic activity due to low substrate levels or high inhibitor concentrations in the cultivation medium became obvious from the FIA signals.

Bacteriological Techniques↗
PubMed1991

On-line determination of glucose concentration throughout animal cell cultures based on chemiluminescent detection of hydrogen peroxide coupled with flow-injection analysis.

A flow-injection analysis (FIA) system for the on-line determination of glucose in animal cell cultures is described. The system is based on immobilized glucose oxidase (GOD). The hydrogen peroxide generated in the enzyme reaction is determined via a highly sensitive chemiluminescent reaction with luminol. Based on the measurement of the maximum emitted light intensity, the system was able to analyse hydrogen peroxide over the concentration range of 10(-7) to 10(-2) M. For glucose determination, the system has a linear range of 10(-5) to 5 x 10(-2) M glucose, with an r.s.d. of 3% at the 1 mM level (5 measurements). The influence of luminol and buffer concentrations, pH and temperature on the chemiluminescent reaction were investigated. The enzyme reactor used was stable for more than 4 weeks in continuous operation, and it was possible to analyse up to 20 samples per h. The system has been successfully applied to on-line monitoring of glucose concentration during an animal cell culture, designed for the production of human antithrombin III factor. Results obtained with the FIA system were compared with off-line results, obtained with a Yellow Springs Instrument Company Model 27 (YSI).

Animals↗