Synthesis and Application of a Novel Ligand for Affinity Chromatography Based Removal of Endotoxin from Antibodies

Current technologies to endotoxin detection and removal for biopharmaceutical purification

Endotoxins are the major contributors to the pyrogenic response caused by contaminated pharmaceutical products, formulation ingredients, and medical devices. Recombinant biopharmaceutical products are manufactured using living organisms, including Gram-negative bacteria. Upon the death of a Gram-negative bacterium, endotoxins (also known as lipopolysaccharides) in the outer cell membrane are released into the lysate where they can interact with and form bonds with biomolecules, including target therapeutic compounds. Endotoxin contamination of biologic products may also occur through water, raw materials such as excipients, media, additives, sera, equipment, containers closure systems, and expression systems used in manufacturing. The manufacturing process is, therefore, in critical need of methods to reduce and remove endotoxins by monitoring raw materials and in-process intermediates at critical steps, in addition to final drug product release testing. This review paper highlights a discussion on three major topics about endotoxin detection techniques, upstream processes for the production of therapeutic molecules, and downstream processes to eliminate endotoxins during product purification. Finally, we have evaluated the effectiveness of endotoxin removal processes from a perspective of high purity and low cost.

Sterilized recombinant spider silk fibers of low pyrogenicity

We have recently shown that it is possible to recombinantly produce a miniature spider silk protein, 4RepCT, that spontaneously self-assembles into mechanically stable macroscopic fibers (Stark, M.; Grip, S.; Rising, A.; Hedhammar, M.; Engstrom, W.; Hjalm, G.; Johansson, J. Macroscopic fibers self-assembled from recombinant miniature spider silk proteins. Biomacromolecules 2007, 8 (5), 1695-1701). When produced as a soluble fusion protein (with thioredoxin) in Escherichia coli , the spider silk protein can be subjected to several purification steps without aggregating. Here, combined purification and endotoxin removal is achieved using a simple cell wash procedure, protein affinity purification, and LPS depletion. No toxic chemicals were included in the process and the protein retained its ability to self-assemble into fibers. With this method, fibers with pyrogenicity corresponding to less than 1 EU/mg could be recovered. Moreover, the fibers could be sterilized through autoclaving with retained morphology, structure, and mechanical properties. This implies that this recombinant silk is suitable for usage as biomaterial, which is further supported by data showing that the fibers allow growth of human primary fibroblasts.

Immobilized proanthocyanidins for the capture of bacterial lipopolysaccharides

Proanthocyanidins (PACs) are an abundant class of compounds found in a variety of plant materials. Here we demonstrate the application of these materials as capture molecules for the removal of bacterial lipopolysaccharide (LPS) from solution. PACs from whole cranberries, grape juice, black tea, and cranberry juice were purified and immobilized onto thiol-activated Sepharose beads. This material was used in pull-down type assays for the capture of LPS. The binding of LPS by PACs has been shown to compete with that of polymyxin B which is known to bind the lipid A component of LPS. Assays conducted in the presence of lipid A verified that at least some component of the LPS binding activity of the PACs is via the lipid A moiety. Molar comparison of polymyxin B to proanthocyanidins indicated that the Sepharose immobilized PACs have a binding affinity for LPS similar to that of polymyxin B.