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目的:探讨放射性核素125I与神经生长因子(nerve growth factor,NGF)偶联的最优反应条件。方法:采用联结标记法进行125I与神经生长因子偶联反应,在125I投料量固定为37 MBq的条件下,改变NGF的投料量分别为20,50,100,150μg,同样的条件下反应后以三氯醋酸沉淀法计算产率。将产物保存于4℃,于1,2,3,5,7天,2,3,4周时间点检测产物的放射性化学纯度,评价产物的体外稳定性。结果:当NGF投料量由20μg增加到50μg时,125I-NGF产率由76.6%迅速增加到79.0%,当继续增加NGF投料量至150μg时,125I-NGF产率仅增加1.2%。经过连续4周观测,本标记方法的产物125I-NGF在体外4℃储存条件下未发现明显脱碘,放射化学纯度始终大于80%。结论:125I与神经生长因子偶联的理想原料配比为37 MBq125I与50μg NGF进行反应,该条件下的产物125I-NGF放射性浓度为97.31 MBq/ml,放射性比活度为584.6 MBq/mg。
Objective: To investigate the optimal reaction conditions for coupling of 125I with nerve growth factor (NGF). Methods: The conjugate labeling method was used to carry out the coupling reaction of 125I with nerve growth factor. The dosage of NGF was changed to 20, 50, 100 and 150μg respectively under the condition of a fixed dose of 125I at 37 MBq. Under the same conditions, Precipitation method to calculate the yield. The product was stored at 4 ° C and the radiochemical purity of the product was measured at 1, 2, 3, 5, 7, 2, 3, and 4 weeks to evaluate the in vitro stability of the product. Results: When the dosage of NGF increased from 20μg to 50μg, the yield of 125I-NGF increased rapidly from 76.6% to 79.0%. When the dosage of NGF was increased to 150μg, the yield of 125I-NGF increased only 1.2%. After 4 weeks of continuous observation, 125I-NGF, a product of this labeling method, showed no significant deiodination at 4 ℃ in vitro and the radiochemical purity was always higher than 80%. CONCLUSION: The optimal ratio of 125I to NGF is 37 MBq125I and 50 μg NGF. The radioactive concentration of 125I-NGF under this condition is 97.31 MBq / ml and the specific activity of radioactivity is 584.6 MBq / mg.