« BIOPROCESSING understanding, characterization, and validation,2 have resulted in
the availability of more efficient process development tools. One approach is the use of high-throughput technologies that rely on either
The successful application of high-throughput screening significantly scaled-down experimental methods or other
miniaturized systems that can generate greater information about a unit operation in shorter periods of time while consuming less material.3-5
and mini-systems has been reported in many areas related to the development of biomanufacturing processes, such as clone screening and selection.6-8
Micro- and mini-bioreactors with working volumes of 0.7 mL to 500 mL that incorporate mixing, mass transfer, and control software comparable to a production bioreactor have been developed to allow cost- and time-efficient simulation of larger bioreactors. Today, many companies use miniaturized high-throughput cell culture development technologies to rapidly and efficiently define critical process parameters, followed by traditional laboratory-scale process development to confirm the details of individual unit operations. This approach can expand the total knowledge base on which a process is developed, thereby leading to a more robust and fully controllable manufacturing process.
One of the first high-throughput cell culture systems was the SimCell Micro Bioreactor,9
which used a mini-bioreactor card containing
6 individually controlled 700-µL chambers. Using robotics and associated automated controls, the SimCell could perform experiments using up to 1200 cell culture chambers in a single operation. However, the instrument was not widely adopted due to the high cost and the requirement
to have specially trained operators to run the
experiments. In addition, the throughput was considered almost too high to provide useful information for early development.
Pall Corporation offers the Micro-24 system that can run up to 24 simultaneous experiments with independent control and monitoring of each bioreactor’s gas supply, temperature, and pH. Each bioreactor has a working volume of up to 10 mL, providing a low- volume, high-throughput option for efficient cell culture development. The Micro-24 can be used for microbial fermentation or mammalian cell culture and is a cost-effective alternative to the SimCell product.
The Advanced Microscale Bioreactor (ambr™) from Sartorius Stedim Biotech is a newer micro-reactor product that has been widely implemented. The system offers parallel processing and evaluation in an automated workstation with 24 or 48 stirred-tank micro- bioreactors with working volumes of 10 mL to 15 mL. The bioreactors have individual monitoring and control of temperature, DO, and pH.10 Sartorius Stedim Biotech has also introduced the ambr250 system that provides for slightly larger working volumes of 100 mL to 250 mL.11
Intermediate scale systems such as the DASGIP Parallel Bioreactor System12
from Eppendorf contain multiple bioreactors in the range
of 35 mL to 4 L that can be operated on a parallel basis with a single integrated controller. These larger bioreactors enable the assessment of gassing in the headspace, antifoam, and other parameters that are not accessible in the micro-reactor format. This system can integrate with analyzers such as cell counters and high-performance liquid chromatography, which is not available at the micro-reactor scale.
Another intermediate scale system called the Biopod is available from Fogale Nanotech.13
bioreactors (with either 80 mL or 800 mL of working volume) at once. Additional systems for running multiple mini-bioreactors are also available from M2p-labs14
and other vendors. Some companies have
also built their own high-throughput mini-bioreactor systems for process development.15
These systems are valuable for transitioning
processes from the micro-reactor scale into a format that is fully transferable to production scale while still enabling some final evaluation and definition of critical process parameters.
Several publications highlight the usefulness and reliability of mini- bioreactor systems in cell culture development. In a study by Legmann, et al,16
data from 700-μL SimCell mini-bioreactors were compared to a
3-L bioreactor for the development and optimization of a cell culture process for an anti-interleukin-1 β monoclonal antibody (MAb). Excellent agreement was observed between the mini-bioreactor data and data from the conventional bioreactor. Regression analysis of the data showed that the correlation factors for each parameter measured were >0.84 and the product quality profiles were very similar.
Amanullah et al17 described the use of the SimCell for fed-batch
cultivation of a glutamine synthetase (GS)-Chinese hamster ovary (CHO) cell expressing a model IgG4 MAb. Cell growth, process parameters, metabolic titer profiles, and protein titer profiles were compared to those from shake flask, benchtop, and pilot- scale bioreactor cultivations and found to be within +/-20% of the historical averages.
In another study, Hsu et al18 compared 4 recombinant CHO cell lines
in a fed-batch process in the ambr™ system, shake flasks, and 2-L benchtop bioreactors. Cultures in ambr™ matched 2-L bioreactors in controlling the environment (temperature, DO, and pH) and in culture performance (growth, viability, glucose, lactate, Na(+), osmolality, titer, and product quality). Cultures in shake flasks did not show comparable performance to the ambr™ and 2-L bioreactors.
Rameez et al3 compared the ambr™ system to conventional bioreactor
systems for their performance in MAb production in a CHO cell line. The ambr™ system was found to produce cell culture profiles that matched across scales of 3-L, 15-L, and 200-L stirred tank bioreactors. The processes used included complex feed formulations, perturbations, and strict process control within the design space, in-line with processes used for commercial-scale manufacturing of biopharmaceuticals. As Rameez et al3
noted, “Changes to important process parameters in
ambr™ resulted in predictable cell growth, viability, and titer changes, which were in good agreement with data from the conventional larger scale bioreactors. Additionally, the miniature bioreactors were found to react well to perturbations in pH and DO through adjustments to the Proportional and Integral control loop.”
The data reported in these studies demonstrate the utility of
high-throughput systems for cell culture development. They also demonstrate that conventional bioreactors can be adequately modeled using micro- or mini-bioreactors and that such systems allow for the investigation of culture conditions at greater statistical depth than can be performed in a conventional bioreactor. High-throughput cell culture technologies can be an effective tool for the development
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This system is capable of running 8 mini-
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