188Re标记Morpholino寡核苷酸体外稳定性及生物分布

目的 采用治疗性核素铼188(rhenium- 188,188Re)标记Morpholino寡核苷酸,探讨其作为治疗性药物的可能性.方法 以硫乙甘肽(Mercaptoacetyltriglycine,MAG3)作为双功能螯合剂,采用间接标记法,试验不同标记条件对标记率的影响.标记完成后检测生物活性、体外稳定性及正常小白鼠的体内分布.结果 在最佳标记条件下,Morpholino的标记率为65％±12％,纯化后放化纯度＞93％,比活度为(2.37±0.32)MBq/μg.稳定性检测发现,标记物在体外出现再氧化,导致188Re-Morpholino出现解离.加入抗氧化剂抗坏血酸(VitC)后可以显著提高体外稳定性.正常鼠生物分布显示,Morpholinos 主要通过肾脏排泄,甲状腺及胃的摄取明显高于其他器官.结论 以MAG3作螯合剂,188Re可以成功标记Morpholino寡核苷酸；188Re-Morpholino标记物体外稳定性较差,虽然加入抗氧化剂可以提高体外稳定性,但标记物在体内仍出现解离,因此,目前的标记方法可能不适合作为治疗药物.

In vitro stability of 188Re-labeled morpholino oligonucleotide and its distribution in mice

Objective To study the possibility of rhenium-188(188Re)-labeled morpholino oligonucleotide as a therapeutic drug.Methods Mercaptoacetyltriglycine(MAG3) was used as a bifunctional chelater to test the effect of 188Re-labelled morpholino oligonucleotide on labeling rate.Biological activity,in vitro stability and distribution of 188Re-labeled morpholino oligonucleotide in normal mice were detected.Results The labeling rate of 188Re-labeled morpholino oligonucleotide was 65%±12% with a radiochemical purity of over 93% and a specific activity of(2.37±0.32)MBq/μg.Re-oxidation of markers occurred in vitro,which caused disassociation of 188Re-labeled morpholino oligonucleotide.Addition of anti-oxidant and ascorbic acid into 188Re-labeled morpholino oligonucleotide could significantly improve its in vitro stability.188Re-labelled morpholino oligonucleotide was mainly excreted through the kidneys.Its uptake was significantly higher in thyroid and stomach.Conclusion MAG3 can label 188Re-labeled morpholino oligonucleotide with a poor in vitro stability.Addition of anti-oxidant into 188Re-labeled morpholino oligonucleotide can improve its in vitro stability,but the markers will disassociate in vivo.Thus,188Re-labeled morpholino oligonucleotide cannot be used as a therapeutic drug.