Chemical Modification Of SOD With Heparin And N,N,N-Trimethyl Chitosan And Studies On The Structure-Activity Relationship Of The Conjugates And Their Effects On Radiation Injury

The free radicals induced by ionizing radiation, especially reactive oxygen species (ROS), are one of the main reasons of radiation injury. The role of ROS in radiation injury and the potential of antioxidants in reducing these deleterious effects have been studied for more than 50 years. It has been proved that external superoxide dismutase (SOD), with superoxide anion freeradical (O₂^·|-) as its substrate, has certain effects in preventing and curingradiation injury. But external SOD has some disadvantages such as low stability, short half-life, antigenicity, etc., which could be overcome by chemical modification. Lots of reports have proved that heparin, one kind of mucopolysaccharides, could promote the release of SOD combined on the surface of endothelial cells(EC) thereby inhibited the role of oxygen free radicals besides its anticoagulant effect. In addition, heparin also gets high attention in medical field for its function of preventing and curing lung injury. It has been reported that chitosan has wound-healing, free radical scavenging and radioprotective effects. It has been demonstrated that cationed SOD exhibited an excellent inhibitory effect on free radicals release from the macrophages due to its higher macrophages targeting property. In this paper heparin-SOD(HEP-SOD) and N,N,N-trimethyl chitosan-SOD (TMC-SOD) were prepared and the secondary structures and the effects on radiation injury of the polysaccharide-SOD conjugates were studied.1 Preparation of HEP-SOD and TMC-SODSOD was modified with NaIO₄ activated heparin in pH9.5, 0.3mol/L carbonate buffer and the resulting product was determined by electrophoresis.