PEGylation of recombinant hirudin in mixed aqueous–organic solutions

Serious loss of polyethylene glycol (PEG) reagent is confronted during PEGylation of proteins in mildly acidic aqueous solution. In this study, a novel approach of PEGylation of recombinant hirudin variant-2 (HV2) with monomethoxy-PEG-succinimidyl carbonate (mPEG-SC) was developed in six mixed aqueous–organic solutions. The PEGylation efficiency in each mixed solutions was greater than that in pure aqueous solution. Structure analysis of HV2, hydrolysis kinetics of mPEG-SC, and PEGylation kinetics of HV2 in different solutions revealed that solvent effects occurred in mixed aqueous–organic solutions. According to the dominant solvent effect of PEGylation acceleration and mPEG-SC hydrolysis inhibition, the selected mixed aqueous–organic solutions could be divided into different types (PEGylation-driven, mPEG-SC hydrolysis-driven, both PEGylation and mPEG-SC hydrolysis-driven). In aqueous-DMSO solutions, the desired yield (approximately 50%) of mono-PEG-HV2 was achieved under the optimized reaction conditions. The optimal usage of PEG reagent could decrease 3–5 fold compared with that of PEGylation in pure aqueous solution. The mono-PEG-HV2 could restore its structure and bioactivity after being purified into aqueous solution. This study demonstrated that PEGylation of proteins in mixed aqueous–organic solutions could be used as an alternative method to PEGylation in pure aqueous solution.

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