Disposable chromatography technologies: a review of solutions to a downstream processing bottleneck.
Through the use of various ion exchange technologies, ligand formats, device construction and innovative scaling technologies, disposable and even single-use chromatographic separations and purification operations are now feasible.
Traditional Columns and Membrane Chromatography Adsorbers: Traditional column chromatography relies on molecular diffusion to transport the target species through the microporous structure of the resin beads to internal binding sites. Column chromatography for flow-through anionic exchanger polishing steps operate at flow rates measured in centimeters/hour. This relatively slow passage needs rather large diameters columns, upward of 1.0 meter +, to achieve reasonable flow rates. At these diameters, fill volumes will require resin beads in the hundreds of liters, at substantial cost. Much of the columns adsorptive capacity may not be maximized in order to reach acceptable flow rates. There are also difficulties when purifying large molecular weight molecules, such as host cell proteins (HCP), DNA, viruses, endotoxins and large proteins. These species present diffusion challenges due to their size and restriction to move freely into the micropores of resin beads.
These drawbacks to anionic exchange columns promoted the development and use of membrane adsorber chromatography. A first use was for contaminant reduction/removal, e.g., HCP DNA, etc. and then subsequently for use in protein purification applications. The contaminants are directly bound to the membrane positively charged (+) ligands, eliminating the need for diffusive migration into resin beads. The higher flow rates of membrane adsorbers is due to the open pore structure of the membrane, typically 5-8 pm, which offer no restriction to very high molecular weight species, and are coupled by anionic species that have high binding capacities, often equivalent to traditional columns. The higher flow rates, measured in ml/minute, significantly decrease processing times, thusly greatly improving throughput. The membrane structure also significantly decreases hold-up volumes of single-use disposable chromatography devices. The need for high volume buffer rinses to flush high value product is thusly eliminated, another processing cost reduction benefit. The comparable antibody yield for membrane adsorber chromatography is on order with traditional AEX column chromatography.
DISPOSABLE CHROMATOGRAPHY COLUMNS--FEATURES/BENEFITS
Today, there are many disposable chromatography column systems that meet regulatory cGMP requirements and industry standards. Besides the sanitary design, material of construction qualifications, 1Q/0Q/PQ, end-users demand cost reducing processes and systems that provide results in higher yields and product purity.
These key features include reproducibility, scalability, speed, ease of use, operator safety.
Reproducibility: This is a key consideration during column set-up and packing. Reproducible performance as measured by using peak symmetry and elution profiles, which must be achieved each time the column is packed, and/or recycled. Which assumes resin and chromatography bind and elute procedures are identical. Each pre-packed or recycled disposable column must be reproducible from batch to batch.
Scalability: Optimization of the chromatography process, from bench-top small volume column diameters to large process columns must be scalable and reverse scalable for on-going process development trials. The packing and condition steps should generate the same performance regardless of the column diameter. One major failing of many reusable systems.
Speed: The recent gain made in higher upstream protein titers upward of 20-30 g/I, place greater focus on the downstream separation and chromatography purification processes as the bottleneck. Addressing this growing chromatography bottleneck problem, Process Development Groups persistently seek production improvements to speedup the rate limiting chromatography step. Reducing downtime by decreasing the time needed for repeatedly packing and unpacking columns can increase turn-around cycle times thereby increasing production efficiencies. Using pre-packed disposable column systems, the column maintenance time is eliminated. By using this 'plug-n-play' system one can considerably shorten downtime and optimize production cycle time and costs.
Ease-of-Use: The use of either disposable chromatography system, pre-pack recyclable or single-use columns (campaign-type columns) require these systems quickly connect with standardized fittings. The 'plug-n-play' concept as applied to other single-use downstream polymeric devices should apply to these column products as well.
Operational Safety: The benefit associated with single-use disposable biopharm devices also carries over to chromatography products. As with single use devices, the use of sanitizing and cleaning chemicals can be minimized. Since these columns are self-contained units, the risk of accidental chemical exposure and contact with the operator during take-down and set-up and disposal may be greatly reduced or eliminated. Personal Protection Equipment (PPE) may not be required, increasing the comfort and ergonomics of these chromatographic installations
The single-use/disposable chromatography column and membrane chromatography products continue to develop as manufacturers bring new innovative products to the downstream processes. Although membrane chromatography is not a new technology, the recent expansion of salt tolerant absorber devices and newer anionic ligand technologies fulfill end-user demand for more robust and efficient purification steps. Similarly, disposable column chromatography product offerings continue to flow into the downstream processes, from simulated moving bed (SMB) chromatography systems that decrease cycling downtime, to pre-packed and dedicated 'campaign' columns. On the horizon mAb purification by disposable Protein A column replacement may very well be the next DSP bottleneck to he tackled.
By Mark Trotter, President, Trotter Biotech Solutions, Inc.
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|Date:||Apr 1, 2013|
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