Impact of Polymer Bioconjugation on Protein Stability and Activity Investigated with Discrete Conjugates: Alternatives to PEGylation
2018-09-17T00:00:00Z (GMT)
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Covalent attachment
of synthetic polymers to proteins, known as
protein–polymer conjugation, is currently one of the main approaches
for improving the physicochemical properties of these biomolecules.
The most commonly employed polymer is polyethylene glycol (PEG), as
evidenced by extensive research and clinical track records for its
use in biopharmaceuticals. However, the occurrence of allergic reactions
or hypersensitivity and the discovery of PEG antibodies, on the one
hand, and the rise of controlled polymerization techniques and novel
monomers, on the other hand, have been driving the search for alternative
polymers for bioconjugation. The present study describes the synthesis,
purification, and properties of conjugates of lysozyme with poly(N-acryloylmorpholine) (PNAM) and poly(oligoethylene glycol
methyl ether methacrylate) (POEGMA). Particularly, conjugate species
with distinct conjugation degrees are investigated for their residual
activity, aggregation behavior, and solubility, by using a high-throughput
screening approach. Our study showcases the importance of evaluating
conjugates obtained by nonsite-specific modification through isolated
species with discrete degrees of conjugation rather than on the batch
level. Monovalent conjugates with relatively low molar mass polymers
displayed equal or even higher activity than the native protein, while
all conjugates showed an improved protein solubility. To achieve a
comparable effect on solubility as with PEG, PNAM and POEGMA of higher
molar masses were required.
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