^(99m)Tc标记的新型肺癌多肽分子探针及其生物学分布

^(99m)Tc radiolabeling of a novel polypeptide molecular probe for lung cancer and its biodistribution in animals

目的探讨99mTc标记特异性靶向肺癌小分子多肽的标记方法,观察99mTc-多肽在正常动物体内的动力学特性及体内生物学分布特点。方法采用NHS-MAG3双功能螯合法进行99mTc标记小分子多肽(cNGQGEQc),纸层析法测定标记率,通过体外稳定性实验、半胱氨酸置换实验及血清蛋白结合实验评价99mTc-多肽的放化特性,测定标记物静脉注射后在新西兰大白兔不同时相血液放射性清除曲线;分别测定经尾静脉注射7.4 MBq标记物后的小鼠体内各脏器质量数和放射性计数,计算各脏器每克组织百分注射剂量率(%ID/g);经耳缘静脉注射37 MBq标记物,应用SPECT显像法观察标记物在大白兔体内的放射性动态分布变化。结果99mTc标记多肽的标记率>90%,室温下和血清中37℃下放置12 h放化纯度分别为91%和85%;半胱氨酸置换率<7%;血清蛋白结合率<5%。99mTc标记多肽在兔体内血放射性清除迅速;在小鼠体内清除较快,主要通过肾脏排泄,其余脏器内放射性均较低(P<0.05)。结论99mTc标记基于肺癌特异性靶向多肽的标记方法简单,标记率高,具有良好的体内外稳定性,具有比较理想的体内分布动力学特性。

Objective To develop a method for 99mTc radiolabeling of a small molecular peptide targeting lung carcinoma and observe the biokinetics and biodistribution of the labeled peptide in normal mice and rabbits.Methods MAG3-peptide(cNGQGEQc) was labeled with 99mTc and the labeling rate was determined with paper chromatography.In vitro stability test,cysteine challenge test and serum incubation test were performed for radiochemical evaluation of the labeled peptide.Blood 99mTc-peptide clearance in rabbits was evaluated by determining blood radioactive concentrations at different time points after injection of 37 MBq99mTc-peptide,and its dynamic distribution was investigated by SPECT imaging.The percent injected dose per gram of tissue was calculated for each organ of mice injected intravenously with 7.4 MBq 99mTc-peptide based on gamma counter readings.Results The labeling rate of99mTc-peptide exceeded 90%,and the radiochemical purity was 91% after placing for 12 h at room temperature and 85% after incubation at 37℃with human serum.The cysteine replacement rate was less than 7%,and the binding rate of99mTc-peptide with serum proteins was below 5%.SPECT imaging showed that the labeled peptide could be quickly cleared from the blood in normal animals primarily through the kidneys,and the radioactivity in other tissues and organs remained low.Conclusion 99mTc-peptide can be easily prepared with a high labeling yield.With good stability both in vitro and in vivo,99mTc-peptide can be quickly cleared from the blood and excreted though the kidney with ideal biodistribution and biokinetics in vivo.