Biomedical Engineering Reference
In-Depth Information
reduction in the feed protein requirement by over 100-fold for breakthrough
measurements and 3,000-fold for elution measurements between microfluidic and
30-mL laboratory columns.
5 Related Issues and Challenges
5.1 Analytics
Although scale-down work (especially that used robotically in a high-throughput
format) reduces manual workload and increases throughput, this has the potential
to shift the bottleneck away from process characterisation and over to the analysis
[ 7 ]. To achieve the complete throughput benefits offered by high-throughput
techniques requires one to address the potential impact of the analytical bottleneck.
Depending upon the method used and the total number of samples, it is possible
for the analysis to take longer than the primary high-throughput characterisation
itself. In these circumstances, it is necessary to reduce analytical timescales as far
as possible, and suitable approaches include:
• Using previously gathered knowledge to focus scale-down studies towards those
regions of a search space that are most likely to be process-relevant, thus
improving the intrinsic value of any analysis carried out in those areas;
• Stratifying the analysis by performing coarse screens such as simple absorbance
measurements during initial studies and switching later to more rigorous, time-
consuming techniques such as HPLC or ELISA for more detailed assessment of
specific product or impurities. This minimises the upfront analytical burden and
means that only the most feasible regions are subject to the most time-consuming
assays;
• Managing data generated by the use of high-throughput analytics in an efficient
way is important; For example, the 96-well batch format is compatible with a
number of medium-throughput analytical devices such as plate readers for rapid
spectrophotometric measurements. As a consequence, however, scale-down
chromatography may generate very large, complex data sets that require effi-
cient methods for their collection, storage and use. Failure to do so may over-
whelm the capacities that a company has for analysing samples and archiving
the data [ 1 , 18 ];
• Employing high-throughput, parallel assays will become advantageous; com-
mercial systems for doing this include microfluidic gel electrophoresis, chro-
matographic or ELISA-based assays. Since the ultimate aim of scale-down
chromatography is to link such devices with scale-down mimics of other steps
and since the smallest devices may use only minimal feed volumes themselves,
significant loss to analysis or hold-up will mean that insufficient amounts remain
to process in scale-down mimics of subsequent operations. This can force one to
repeat a study to generate enough feed for the next step downstream. By
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