Synthesis and purification of mono-PEGylated insulin

Monomethoxypoly(ethylene glycol) 5000 (mPEG5K) and 2000 (mPEG2K) were activated to produce mPEG-aldehyde with content over 80%. Effects of reaction time, pH and initial molar ratio of mPEG-aldehyde to insulin on synthesis of PEGylated insulin were studied, taking mPEG5K-aldehyde as a model. On the optimized condition, approximately 90% of product was mono-PEGylated insulin. Mono-PEGylated insulin was purified by ion-exchange chromatography. The purity of each component was analysed by RP-HPLC and the results showed an efficient purification. Matrix assistant laser desorption ionization time-of-flight mass spectra demonstrated that the modification site of mono-PEGylated insulin was PheB1. The biological activity of all PEGylated insulin was also evaluated.