PEGylation of Carbohydrates

The advantage of PEGylation of glycan structures attached to proteins is that the reaction can be restricted to the glycosylation sites. Thereby providing the benefits of PEGylation to the product without inactivating the protein due to random multi-step PEGylation. Multi-armed PEGylation with more available sites for glycan attachment can be used to improve carbohydrate interactions with cellular receptors. PEGylation of carbohydrates significantly improves the bioavailability of drugs, especially enzyme inhibitors, or produces polymers with drug encapsulation properties. BOC Sciences has developed several different methods for modifying glycans by covalent attachment to PEG reagents, especially multi-armed PEGs, with the aim of increasing the loading of active glycans. Our PEGylated multivalent glycan molecules have been shown to mediate or inhibit a variety of biological or pathological processes.

What is GlycoPEGylation?

GlycoPEGylation, targeting carbohydrate sites, is believed to result in a more uniform product with lower steric effects. This strategy is based on the discovery that certain pegylated nucleotide sugars can be efficiently transferred to glycan acceptors by corresponding glycosyltransferases. In addition, PEGylation of native glycoproteins can be performed by enzymatic or chemical modification of glycans. Among them, the enzymatic modification reaction of glycans is kinetically controlled, and the amount of PEG added depends on the reaction time. In the chemical modification of glycoprotein PEGylation, a reactive group is created in the sugar of an O- or N-linked glycan by a chemical modification. For example, carbohydrate-specifically modified ricin exhibited better pharmacokinetic properties than peptide amino pegylated or unmodified ricin.

Fig. 1. Activated PEG derivatives for conjugation.

Our Carbohydrate PEGylation Capabilities

• PEGylation of Monosaccharides

Carbohydrate monomers can be obtained by multi-step synthesis starting from readily available diacetone glucose. Currently, PEGylation of monomer carbohydrates is widely exploited. Representative examples include furanpentose derivatives, galactose and mannose. Among them, two hydroxymethylene groups in the pentofuranose derivatives are enzymatically esterified with polyethylene glycol dimethyl ester to generate a sugar-polyethylene glycol copolymer for drug encapsulation. Galactose has also been pegylated and introduced to the surface of polystyrene nanoparticles to increase the interaction with the galactose receptor. In addition, mannose is also pegylated to specifically target the drug to the mannose receptors present in hepatic endothelial cells. With advanced equipment and technology, BOC Sciences provides researchers with technical support for the PEGylation of various monosaccharides. Our PEGylation technology includes random PEGylation and site-specific PEGylation. We are confident in delivering highly reliable and repeatable results.

• PEGylation of Polysaccharides

Currently, PEGylation of polysaccharides has been demonstrated by the application of PEGylation of chitosan and chitosan derivatives in drug development. Chitosan is a polysaccharide obtained from abundant chitin by alkaline or enzymatic degradation. The amino groups of chitosan can be derivatized with PEG chains, thereby changing the physicochemical properties. Examples of polysaccharide derivatization on the hydroxyl groups of chitosan have also been reported. In addition, fructans have also been pegylated by reacting hydroxyl-activated polysaccharides with amino-terminated methoxy PEGs. This reaction was applied to inulin and Radix Ophiopogonis polysaccharides to improve their pharmacokinetic properties. The polysaccharide PEGylation strategy of BOC Sciences covers chitosan, fructan, inulin, ophiopogon polysaccharide and dextran, etc. Our PEGylation technology supports PEG derivatives of various molecular weights and structures, such as linear, branched, PEG dendrimers, and multi-armed PEG molecules.

Reference

1. Lederkremer, R.M. et al. Carbohydrate PEGylation, an approach to improve pharmacological potency. Beilstein J. Org. Chem. 2014, 10: 1433-1444.