Purification of rPEG via Ammonium Sulfate Precipitation:
A Prototype Amorphous and Flexible Polymer
Lea Simon,a Philip Dreiera and Holger Frey*a
aDepartment of Chemistry, University of Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany
*hfrey@uni-mainz.de
Polyethylene glycol (PEG) has long been regarded as the gold standard in pharmaceutical and biomedical applications due to its chemical inertness, biocompatibility, and unique stealth properties.[1] However, recent studies have demonstrated that PEGylated therapeutic agents can induce severe side effects due to the formation of anti-PEG antibodies, including complement-activated pseudoallergic reactions and accelerated blood clearance.[2,3] Frey and co-workers identified a random copolymer of ethylene oxide (EO) and racemic glycidyl methyl ether (GME) (randomized PEG isomer, “rPEG”) as a promising alternative to PEG.[4] Due to the lack of crystallinity, the purification of rPEG is challenging, making purification methods established for PEG, such as precipitation in diethyl ether, inapplicable.
This work presents an optimized purification process for rPEG using the ammonium sulfate precipitation method, a widely used technique for protein purification.[5] The method exploits the salting-out behavior of water-soluble polymers at high ionic strength, causing the polymer to precipitate while other substances remain dissolved in the solution. rPEGs of varying size and GME content, synthesized via anionic ring-opening copolymerization, were efficiently purified using ammonium sulfate precipitation, achieving high isolation yields of up to 97%. The resulting isolated polymers exhibited high purity, as confirmed by nuclear magnetic resonance spectroscopy, size-exclusion chromatography, and mass spectrometry. Due to its cost-effectiveness and rapid execution, this method offers a compelling alternative to established purification techniques such as dialysis or preparative high-pressure liquid chromatography. Consequently, ammonium sulfate precipitation emerges as a promising method for the purification of water-soluble polyethers, with potential to expand its scope beyond rPEG.
References:
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