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  • 1
    Electronic Resource
    Electronic Resource
    Batch and semicontinuous aggregation and sedimentation of hybridoma cells by acoustic resonance fields (1995)
    s.l. : American Chemical Society
    Biotechnology progress 11 (1995), S. 146-152 
    Details
    ISSN: 1520-6033
    Source: ACS Legacy Archives
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bp00032a005
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  • 2
    Electronic Resource
    Electronic Resource
    Expansion of Hematopoietic Progenitor Cell Populations in Stirred Suspension Bioreactors of Normal Human Bone Marrow Cells (1994)
    [s.l.] : Nature Publishing Company
    Nature biotechnology 12 (1994), S. 909-914 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We have investigated the potential of stirred suspension cultures to support hematopoiesis from starting innocula of normal human bone marrow cells. Initial studies showed that the short–term maintenance of both colony–forming cell (CFC) numbers and their precursors, detected as ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0994-909
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  • 3
    Electronic Resource
    Electronic Resource
    Acoustic Cell Filter for High Density Perfusion Culture of Hybridoma Cells (1994)
    [s.l.] : Nature Publishing Company
    Nature biotechnology 12 (1994), S. 281-284 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We have developed a flow–through device which uses high frequency, low energy ultrasonic resonance fields to transiently aggregate hybridoma cells and return them by sedimentation to a perfusion bioreactor. The system retained up to 99 percent of the inflowing viable cells with no measurable ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0394-281
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  • 4
    Electronic Resource
    Electronic Resource
    Protein transport in ultrafiltration hollow-fiber bioreactors (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 415-425 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A 1-D model, which neglects radial variations, describes the hydrodynamics of cell-free ultrafiltration hollow-fiber bioreactors (HFBRs) and the transport of highmolecular-weight proteins trapped in the extracapillary space (ECS). The profiles of radially-averaged protein concentrations predicted by this model are identical to those obtained using a model with radial variations. The model predictions agree well with axial profiles of bovine serum albumin (BSA) and human transferrin concentrations measured in transient and steady-state experiments. The validated model explores the influence of cell culture operating conditions on HFBR protein transport. Increasing protein loading decreases BSA and transferrin polarization in HFBRs operated with unidirectional lumen flow. A relationship developed predicts the protein loading needed to ensure a nonzero steady-state protein concentration throughout the ECS. This critical protein loading depends only on the lumen pressure drop and the ECS protein osmotic pressure. Periodic reversal of the lumen flow direction also decreases protein polarization. The influence of the flow-direction switching time and membrane permeability on the ECS protein distribution is investigated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410222
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  • 5
    Electronic Resource
    Electronic Resource
    Differential stability of proteolytically active and inactive recombinant metalloproteinase in Chinese hamster ovary cells (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 594-600 
    Details
    ISSN: 0006-3592
    Keywords: CHO ; mammalian cells ; metalloproteinase ; recombinant protein production ; expression stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stability of heterologous protein expression during production is critical for regulatory approval of vaccine and therapeutic products. Leishmania GP63, a zinc metalloproteinase that is a potential vaccine candidate, has been expressed on the surface of Chinese hamster ovary (CHO) cells. Flow cytometry was used to follow the stability of GP63 expression. Expression of proteolytically active GP63 (GP63WT) was unstable whether or not methotrexate (MTX) selection was maintained. In contrast, expression of an active site mutant (GP63E265D) was stable under MTX selection. In the absence of selection, the decline in GP63E265D expression was more gradual than the loss of GP63WT expression. Different molecular mechanisms accounted for these losses and resulted in higher growth rate nonproducer populations. A dynamic population model was used to calculate the conversion rates of GP63WT producers to nonproducers. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 594-600, 1997.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Protein adsorption in polysulfone hollow fiber bioreactors used for serum-free mammalian cell culture (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1099-1106 
    Details
    ISSN: 0006-3592
    Keywords: protein adsorption ; hollow fiber bioreactor ; transferrin ; serum-free medium ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The recovery of serum-free medium proteins from poly-sulfone hollow fiber bioreactors (HFBRs) was investigated. More than 99% of the initial transferrin was adsorbed to the hydrophobic hollow fibers within 2 h of HFBR operation. A methodology to minimize transferrin adsorption by pre-adsorption of bovine serum albumin (BSA) was developed. BSA adsorption on suspended cut fibers was virtually complete within 1 h. BSA-coated fibers adsorbed only 5% of the transferrin within 10 days, whereas uncoated cut fibers adsorbed more than 99% of the transferrin within 1 h. An improved HFBR startup procedure, using a BSA-coating step before inoculation, resulted in substantially higher transferrin recovery. Additional factors influenced extracapillary space (ECS) transferrin concentrations. Pronounced downstream polarization of transferrin was observed in the ECS. In addition, the 30-kDa nominal molecular weight cutoff ultrafiltration membranes rapidly leaked transferrin from the ECS to the lumen. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420912
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of mammalian viable cell biomass based on cellular ATP (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 859-864 
    Details
    ISSN: 0006-3592
    Keywords: cell volume ; intracellular ATP ; hybridoma ; biomass ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Analysis of cellular ATP as a means of measuring viable biomass loading was investigated in hybridoma cell culture. ATP analysis by the luciferin-luciferase assay was compared with trypan blue-stained hemocytometer counts. The cell-specific ATP content varied between 2 and 6 fmol per viable cell over a batch culture. ATP levels were highest during exponential growth, and decreased during the stationary and decline phases. Electronic counting and volume measurements were performed to assay the viable cell biomass. Cell sorting, using fluorescein diacetate, was used to separate viable and nonviable cells in cultures with between 35% and 90% viable cells. Viable cells contained over 2 orders of magnitude greater cell-specific ATP than nonviable cells. Cell-specific ATP correlated directly with the viable cell volume rather than viable cell numbers. Over the range of batch culture conditions, ATP analysis should provide a more accurate measurement of hybridoma viable biomass than hemocytometer counts.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390807
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  • 8
    Electronic Resource
    Electronic Resource
    Mammalian cell and protein distributions in ultrafiltration hollow fiber bioreactors (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 902-910 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The heterogeneous nature of hollow fiber reactors for cell cultivation requires special considerations for proper design and operation. Downstream concentration of high-molecular-weight proteins has been measured in the shell side of ultrafiltration hollow fiber bioreactors. This distribution resulted from shell-side convective fluxes which caused a concentration polarization of proteins retained by the ultrafiltration membranes (nominal 3 × 104 D cutoff). Measurements of the axial hybridoma cell distribution also revealed a downstream concentration of viable cells during the first month of perfusion operation. This is believed to result from the shell-side convective flow and its influence on the inoculum and high-molecular-weight growth factor distributions. The heterogeneous distribution of cells leads to reduced cell numbers and reactor productivities. The mechanisms responsible for these phenomena have been investigated and their implications in process design and operation are considered. The heterogeneous protein and cell distributions on the shell side of hollow fiber bioreactors have been reduced significantly by periodic alternation of the direction of recycle flow and the reactor antibody productivities have been doubled.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260360905
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  • 9
    Electronic Resource
    Electronic Resource
    Mammalian cell retention devices for stirred perfusion bioreactors (1998)
    Springer
    Cytotechnology 28 (1998), S. 163-175 
    Details
    ISSN: 1573-0778
    Keywords: centrifuge ; cross-flow filter ; review ; sedimentation ; spin-filter ; ultrasonic cell retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Within the spectrum of current applications for cell culture technologies, efficient large-scale mammalian cell production processes are typically carried out in stirred fed-batch or perfusion bioreactors. The specific aspects of each individual process that can be considered when determining the method of choice are presented. A major challenge for perfusion reactor design and operation is the reliability of the cell retention device. Current retention systems include cross-flow membrane filters, spin-filters, inclined settlers, continuous centrifuges and ultrasonic separators. The relative merits and limitations of these technologies for cell retention and their suitability for large-scale perfusion are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008050202561
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of ultrasonic forces for particle-liquid separations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1727-1736 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The magnitude and direction of the ultrasonic radiation forces that act on individual particles in a standing-wave field were determined using a microscope-based imaging system. The forces are calculated from measured particle velocities assuming that the drag force, given by Stokes' law, is exactly counterbalanced by the imposed ultrasonic forces. The axial primary radiation force was found to vary sinusoidally with axial position and to be proportional to the local acoustic energy density, as predicted by theory. The magnitude of the transverse primary force was determined by two independent methods to be about 100-fold weaker than the axial force. Separation concepts exploiting the transverse force for cell retention have been successful despite the great disparity in magnitude between the axial and transvers-force components. This may be explained by the reduced hydrodynamic forces on aggregated particles in transverse flow due to their alignment in the sound field.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430710
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