Objective To establish a radiolabelling method of specific small molecule peptide for lung cancer targeting with 99mTc by means of NHS-MAG3 as bifunctional chelating agents. Methods The combinatorial library technique was used for screening small molecule peptide specific binding to non-small cell lung cancer cell ( A549 ). Peptide sequence of cNGQGEQc was identified. Chelant NHS-NAG3 was directly conjugated with peptide cNGQGEQc during the synthesis of cNGQGEQc. The optimal labeling conditions and stability in vitro were investigated. Labeling rates was determined by paper chromatography. Results The couple method of NHS-MAG3 with peptide cNGQGEQc by solid-phase synthesis was simplified and improved the couple efficiency. Peptide cNGQGEQc was successfully radiolabeled with 99mTc and the labeling ratio of 85％ was obtained. The radiochemical purity was higher than 95％ by HPLC purification. The labeled compounds of 99mTc-MAG3- cNGQGEQc was stable in vitro at room temperature. Conclusion It is feasible for coupling of NHS-MAG3 to peptide cNGQGEQc and its radiolabeling with high efficiency and better stability in vitro. It appears to be suitable for further experiments requirement in vivo and in vitro application.%目的:研究用NHS-MAG3作为双功能螯合剂进行99mTc标记针对肺癌特异性靶向小分子多肽的核素分子探针的制备方法.方法:利用组合化学肽库技术筛选得到与非小细胞肺癌(A549)发生特异性结合的小分子多肽cNGQGEQc,在合成多肽的过程中直接完成多肽与双功能螯合剂NHS-MAG3的偶联,然后采用氯化亚锡直接进行99mTc的标记,并采用正交设计法进行99mTc最佳标记条件的摸索,纸层析法测定标记率,并观察99mTc标记小分子多肽的体外稳定性.结果:在固相法合成小分子多肽的过程中直接完成NHS-MAG3的联接,简化了偶联步骤,提高了偶联产率.最佳标记条件下标记率约为85%,经HPLC纯化后放化纯度>95%,且在室温条件下和血清中具有较好的体外稳定性.结论:以NHS-MAG3作为双功能螯合剂,用99mTc标记小分子多肽cNGQGEQc,具有良好的标记率和体外稳定性,可满足后续进一步的体内、外实验要求.
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