Polyethylene glycol (PEG) is conjugated to the therapeutic proteins to enhance their circulating half life. PEGylation is a clinically proven strategy for increasing the therapeutic efficacy of protein-based medicines. PEG size and structure is very important in achieving specific properties in the conjugated protein. In this study we have compared the properties of newly synthesized linear PEG-IFN with a same sized (i.e., 30KDa) tri-branched PEG-IFN synthesized in the same lab earlier. For PEGylation reaction, interferon-α2 (IFNα2) concentration in sodium borate buffer pH 8.5 was optimized as 4.0mg/ml. The optimized molar ratio of PEG/IFNα2 was 3:1 instead of 5:1 in the case of tri-branched PEG published earlier. Other parameters of reaction were same as in our previous publication. Mono PEGylation degree reached to 21%. Cation exchange chromatography was used to separate and purify mono PEGylated IFN from the reaction mixture. The purity of mono PEGylated IFN was greater than 95%. It is noticed that PEGylation was more site specific in tri-branched than the linear conjugate. The in vitro bioactivity of linear mPEG-IFN is 10-fold lesser than as reported of tri-branched mPEG3L2-IFN. Thermal stability of linear mPEG-IFN is also smaller than mPEG3L2-IFN at 4°C.
MUHAMMAD FAROOQ SABAR, FARHEENA IQBAL AWAN, MARIAM SHAHID MUHAMMAD USMAN GHANI AND MUSTANSARA YAQUB
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