Objective   To optimize the modification condition of recombinant human ciliary neurotrophic factor (rh-CNTF) with mPEG-ButyrALD (relative molecular weight 20×10).    Methods   Different pH values

temperatures

times and the mass ratio of rh-CNTF and PEG

the concentration of rh-CNTF was used to obtain better rh-CNTF PEGylation. And then the modified rh-CNTF was separated and purified. The in vitro biological activity of rh-CNTF and PEG rhCNTF was measured by chicken embryo dorsal root ganglion (DRG) culture.    Results   The mass ratio of rh-CNTF to PEG

rh-CNTF concentration and pH value showed significant effect on rh-CNTF PEGylation

while time and temperature had little influence on the modification effect. The optimal pH value was 6.5

concentration of rh-CNTF was 1 to 2 mg/ml

and mass ratio of rh-CNTF and PEG was 1∶1 on modification condition. The in vitro biological activity of rh-CNTF was about 2 times higher than that of PEG-rhCNTF in chicken embryo dorsal root ganglion (DRG) culture.    Conclusion   Optimized parameters is obtained to modify rh-CNTF with mPEG-ButyrALD.