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A new microfluidic assembly method for semiconductor‐based biosensors using 3D‐printing technologies was proposed for a rapid and cost‐efficient design of new sensor systems. The microfluidic unit is designed and printed by a 3D‐printer in just a few hours and assembled on a light‐addressable potentiometric sensor (LAPS) chip using a photo resin. The cell growth curves obtained from culturing cells within microfluidics‐based LAPS systems were compared with cell growth curves in cell culture flasks to examine biocompatibility of the 3D‐printed chips. Furthermore, an optimal cell culturing within microfluidics‐based LAPS chips was achieved by adjusting the fetal calf serum concentrations of the cell culture medium, an important factor for the cell proliferation.

This paper describes the design and characterization of a silicon‐based sensor chip for monitoring of fermentation processes. The sensor chip consists of three sensors using different transducer principles. A capacitive electrolyte‐insulator‐semiconductor (EIS) field‐effect structure with Ta2O5as gate material was utilized as pH sensor. An electrolyte conductivity sensor was realized by measuring the impedance between two interdigitated electrodes (IDE). A platinum thermistor was included for temperature measurements. The EIS sensor was integrated into a bioreactor and successfully used for an inlinepH measurement. The layout of the IDE has been optimized with respect to a high cell constant and a wide detectable conductivity range. The integrated platinum thermistor allowed for temperature compensation of the electrolyte conductivity measurement.

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The ex vivoexpansion of human T‐lymphocytes is of increasing importance in medical applications, especially for the adoptive immunotherapy of viral infection and malignant diseases of immunosuppressed patients. In these therapies, the cells of the patient are isolated from the blood and subsequently cultivated, expanded, and / or genetically modified ex vivo. Afterwards, these expanded or modified cells are transplanted back into the patient.

Continuous culture may be an efficient way of producing proteins which are susceptible to secondary processing in the course of a fermentation process. Short residence times in these systems support the production of correctly assembled proteins by avoiding substrate limitations and product inhibitions and also minimize the contact of sensitive bioproducts with degrading enzymes. Thus products of increased stability and integrity are obtained from continuous processes. The downstream process following continuous culture has to be adapted to the specific conditions of continuous fermentations, e.g. large liquid volumes and diluted process solutions. In this paper an approach is shown how a fluidized bed adsorption as first recovery operation may be coupled directly to a continuous production. Immobilized hybridoma cells are cultivated in porous glass microcarriers in a continuous fluidized bed process, the cell containing harvest is purified by fluidized bed adsorption using an agarose based cation exchange matrix. By this coupled mode of operation the large biomass containing harvest volume resulting from the continuous cultivation may be applied directly to a fluidized chromatographic matrix without prior clarification, leading to a particle free and initially purified product solution of reduced volume. In an experimental setup a bench-scale fluidized bed bioreactor of 25 ml carrier volume was coupled to a fluidized bed adsorption column operated with 300 ml of adsorbent. This configuration yielded up to 20 mg of monoclonal antibody per day in a cell free solution at fourfold concentration and fivefold purification. The process was run for more than three weeks with consistent product output.

In the study presented here a laboratory scale (150 ml) fluidized bed bioreactor was used as a tool for making kinetic measurements on the production of monoclonal antibodies (MAb) with a hybridoma cell line. We determined the influence of dissolved oxygen tension (DOT) on the metabolic activity of a hybridoma population immobilized in macroporous collagen microspheres. The data obtained showed a reduction of the metabolic activity of the immobilized population at reduced DOT, the total number of immobilized cells, however, remained constant. At decreasing DOT an increasing lactate yield from glucose at reduced glutamine consumption was noticed, indicating a shift in the pattern of substrate usage. A mathematical description of maintenance metabolism was formulated and the parameters of growth and maintenance requirements were calculated. A growth associated MAb production was determined under the conditions applied leading to space time yields of 225 mg MAb per liter of total reactor volume and day.

Ex-vivoexpansion of primary human hematopoietic progenitor and stem cells is an important technique for clinical applications in cancer and gene therapies. The importance of stromal cells for the cultivation of hematopoietic cells has been shown in numerous studies. Therefore we developed a cultivation system for immobilized co-culture of hematopoietic and stromal cells1)and for screening purposes a miniaturized parallel system, the so-called miniaturized loop-bioreactor2). These cultivation systems are based on the mimikry of the natural compartment of the hematopoieses, the bone marrow. The in vivo-like co-cultivation with stromal cells obtains important biological effects like cell contact and the production of cytokines and extracellular matrix. The immobilization of the cells on macroporous collagen microcarriers simulates the three-dimensional structure of bone marrow. And the optimal feeding of the cells is ensured by the continuous perfusion in the reactor. The miniaturized loop-bioreactor consists of a special stainless steel insert and a magnetic stirbar that are placed in a conventional 12-well culture plate. The microcarriers are placed as a fixed bed in this insert and are flown through with medium by the agitation of the magnetic stirbar. It is possible to investigate in this system twelve parallel experiments. By co-culturing CD34+cells purified from umbilical cord blood with the irradiated murine stromal cell line S1/S1 in the miniaturized loop-bioreactor we have optimized different parameters for the co-cultivation. The experiments were performed over 7 days under standardized conditions with serum containing medium (IMDM) supplemented with IL-3, TPO, FLT-3-ligand, SCF and anti TGF-beta. In first experiments different cell densities on the carrier were analyzed. The optimal cells density ranged from 2.5* 104to 1* 105CD34+cells per reactor system. The cell ratio between CD34+and stromal cells plays an important role in the support of hematopoiesis. The optimal ratio of 1:10 between these cell types was determined by expansion of the CAFC. Another relevant cultivation parameter is the feeding rate. Frequent feeding improved significantly the expansion of MNC, whereas the highest rate of 1/2 reactor volume per day, showed the best results. Based on this parameter optimization we have cultivated CD34+cells in co-culture with S1/S1 (ratio 1:10) and without stroma, both with a feeding rate of 1/2 medium exchange per day for two weeks in the miniaturized loop-reactor. The positive effect of the stromal cells is demonstrated by a strong increase in the expansion of MNC (454 fold vs 180 fold stroma free) and CFC (26 fold day 10). The stroma containing system generated also the greater CAFC output compared to the stroma free system (4.5 fold vs 2 fold). These results indicate that the novel miniaturized loop-reactor is a very suitable system for the cultivation of primary human hematopoietic cells and for the screening of various culture parameters. Using this system the positive effect of a stromal based and frequently fed cultivation strategy was proven.