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Vaccine Purification – A Look Back at Multicomponent Shaped Fibers
Posted on February 13th, 2017 by Syed Ali Ashter in New Materials & Applications
With complex processes requiring specialized equipment and the need to increase yields and lower the cost, there has been a strong drive in industry to find a solution. Replacement of resin with a low-cost thermoplastic fiber in a Chromatography-based purification process can be one such area.
Tangential flow filtration (TFF), gradient centrifugation (GC) and chromatography are typically three main processes used in purification of vaccines and in other therapeutic applications. Unlike, TFF and GC processes, chromatography provide high yields and is significantly scalable. Chromatography uses commercially available bead based resins to purify vaccines by using bind and elute technique. Small pore sizes of these resins compared with the larger virus particle size result in low binding capacities and thereby translate to high cost. As an alternative, fibers providing with high surface area can be used as a replacement for the bead-based resins.
What are Multicomponent Fibers?
Multicomponent fibers known also as bicomponent fibers comprises of two polymers that are extruded together. Each polymer has unique properties with different or similar chemical composition. Multicomponent fibers are extruded in five different forms depending on the applications – a) core and sheath, b) side by side, c) tipped, d) micro-denier, and e) mixed fibers. (Source: Hills, Inc., West Melbourne, FL, www.hillsinc.net). The fiber shapes are produced using a bi-component fiber spinning machine from Hills, Inc. Shaped bicomponent fibers are prepared using commercially available fiber spinning equipment and custom-designed fiber die stacks (Source: U.S. Patent No. 5,162,074). Two single-screw extruders feed thermoplastic material into a common spin head. The spin head contains a die stack that splits and redirects the melt flow into separate filaments which are collected after exiting through a spinneret. After extrusion, the secondary material is removed typically by washing external sheath by solvent (Source: U.S. Patent No. WO 2014120387 A1).
Development of Winged Fibers: Allasso’s Nano-Channel™ Technology
Allasso Industries, Rayleigh NC, developed multicomponent shaped fiber with high surface area using patented Nano-Channel™ technology (Source: www.allassoindustries.com). The fiber included a coextruded internal fiber and an external sheath that is washed with a solvent to remove the dissolvable external sheath (Figure 1). The resulting winged fibers have a high surface area because of their structure, which includes a 16 mm core surrounded by wings extending outwardly 3-5 mm on either side of the core. It has channels that are 1 micron or less in width formed between adjacent wings to form paths for the capture and/or to transport of gases, liquids or particles. The typical cross-sectional dimension for the winged fiber is 16.6 mm in length and 9 mm in width. This provides a fiber of about 1.5 denier. The advantages of the winged fiber are its (1) high surface area, (2) strength and rigidity, and (3) it is inexpensive compared to traditional chromatography beads. These winged fibers unlike the beads can be used as cut fibers or continuous fibers and the chromatography columns can be optimized for efficiency, pressure drop, and column life. (Source: U.S. Patent No’s. US 20120148841, US 20130133980, and US 20130216829).
Figure 1: Nano-Channel™ Technology to produce winged fibers (Courtesy: Allasso Industries, Rayleigh NC; www.allassoindustries.com)
Chromatography Winged Fiber Media
EMD Millipore Corporation used principles of coextrusion to extrude multicomponent shaped fibers, followed by extraction step to remove the dissolvable external sheath layer. A desired ligand functionality on the surface of the fiber was provided using their tentacle technology (U.S. Patent No. US 20120029176 A1). The ligand is capable of selectively binding viruses from a cell culture feed stream, such as by ion- exchange. Since the virus binding occurs only on the surface of the fiber, there are no size exclusion issues with virus binding as seen in bead-based bind/elute systems. Furthermore, since the virus particles can be transported directly to the ligand site by convection, there are no diffusion limitations in the system and the vaccine feed stream, for example. These fibers when packed in a chromatography column at packing density of between 0.1-0.4 g/ml, and at a bed height of 1-5 cm provides sufficient flow uniformity for acceptable performance in a chromatographic evaluation. The functionalized packed fibers can also be delivered in a dry, prepacked form. (Source: U.S. Patent No. WO 2014120387 A1).
Replacement of bead-based resin with multicomponent shaped fibers open range of opportunity for purification/separation industry. In addition to the low cost in processing the fibers, high surface area of the fibers along with the ligand functionality on the surface significantly increases the binding capacity. Thus, increasing the total yield significantly.
All opinions shared in this post are the author’s own.
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