The biopharmaceutical industry has experienced remarkable progress in the upstream production capacity of life-saving proteins. This is while the downstream processing has failed to keep pace, including unit operations which are working close to their physical limit with no economy of scale. Column chromatography which is an integral unit in different stages of downstream purification is considered as the major bottleneck in this section. The packed-bed resin media is costly and the processes are labor-intensive and extremely time consuming. Membrane chromatography which uses a stack of adsorptive membranes as the chromatographic media is one of the most promising alternatives for conventional chromatography techniques. The performance of membrane adsorbers is consistent over a wide range of flow rates which is owing to the dominance of convective solute transport as opposed to the diffusion-based nature of mass transfer within the pores of the resin beads. This translates to much higher productivity and considerably lower buffer consumption (even as high as 95%), leading to much lower overall processing costs. The other advantages are significantly lower footprints and decreased pressure drops, both contributing to diminished capital costs. Membrane adsorbers are greatly scalable and used in a single-use manner. The latter eliminates the cleaning and validation steps and brings about much shorter processing times and higher flexibility in process development.
Due to the performance advantages of membrane chromatography, this technique is now widely used in purification of high volumes of samples in late-stage polishing. Currently available membrane adsorbers have radial-flow spiral-wound configuration with high frontal surface area to bed height ratio according to which dilute impurities are removed in a flow-through format at very high flow rates and low pressure drops. Nevertheless, they fail to give high-resolution for bind-and-elute separations which makes them unsuitable for many unit operations, highly restricting their application. Severe design deficiencies such as large dead volumes and varying membrane area over the bed height result in broad and poorly resolved peaks.
Herein, a novel device design was successfully developed which addresses the abovementioned shortcomings. The laterally-fed membrane chromatography (LFMC) devices house a stack of rectangular membrane sheets with two rectangular lateral channels on both sides of the stack as the feed and permeate channels. The design offers balanced pressure over the sides of the stack as well as even solute flow path lengths due to which the solute residence time is very uniform. Also, the small dead volumes minimize the dispersion effects. These features make the LFMC technology highly suitable for bind-and-elute applications, the improvement which is brought about by a simple design. The devices are easy to fabricate and highly scalable.
The LFMC devices containing cation-exchange (CEX) membranes with 7 mL bed volume were examined for bind-and-elute separation where they outperformed the equivalent commercially available radial-flow devices. The design was further modified to give even lower dead volumes and more cost-effective fabrication. The latest embodiment of the device gave resolutions which were comparable with the ones obtained with the commercially packed resin columns in 1 mL and 5 mL scale with consistency over wide range of flow rates. The results were all acquired using a three component model protein system. Upon the approval of suitability of the device for bind-and-elute separation, the CEX-LFMC was used for purification of monoclonal antibodies (mAbs), the largest class of biopharmaceuticals. The device showed great performance in separation of mAb charge variants when extensively shallow gradients (60 membrane bed volumes) were required. The devices offered very stable conductivity gradients at high flow rates. LFMC devices in three different preparative scales gave great performance in separation of mAb aggregates which was approved for different mAb samples. The other application studied with the CEX-LFMC devices was the single-step preparative purification of mono-PEGylated proteins which is as well very challenging due to the physicochemical similarities between the target molecules and the impurities. Collectively, the LFMC devices combine the high-resolution with high-productivity which is highly desirable in downstream purification of biological molecules with great potential to expand the application of membrane chromatography.
Finally, the LFMC devices were modified to adapt the analytical scale where they were integrated with a stack of hydrophilized PVDF membranes. The device successfully delivered ultra-fast separation of mAb aggregates in less than 1.5 minutes based on hydrophobic interaction membrane chromatography (HIMC). The assay times achieved with the HI-LFMC technique outclassed the currently available ultra-high performance chromatography (UPLC) methods at the same time with being extremely cost-effective. The application of the LFMC technology in analytical scale has great potential to offer cheap and rapid analysis in process development and quality control section of biopharmaceutical manufacturing. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21234 |
| Date | January 2017 |
| Creators | Madadkar, Pedram |
| Contributors | Ghosh, Raja, Chemical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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