Prolongation of the serum half-life period of superoxide dismutase by poly(ethylene glycol) modification

Superoxide dismutase (SOD) was chemically modified using poly(ethylene glycol) (PEG) with different molecular weights to prepare PEG-SOD conjugates with different extents of modification. The body distribution of the conjugates intravenously injected to mice was investigated to assess the influence of modification on the serum half-life period of SOD. The SOD modification with PEG was effective in lowering the elimination rate of SOD from the blood circulation without any change in the distribution pattern of organs other than the kidney. The molecular weight of PEG used for modification and the modification extent have a minimum effect on the half-life of the SOD. The half-life of the SOD and its PEG conjugates have a similar dependency on the apparent molecular weight as the PEG molecules. This indicates that the half-life of SOD and the PEG conjugates are mainly determined by their molecular size.