铜64硫化铜-多肽复合纳米微粒（64CuS-Bom）前列腺癌靶向显像的基础研究

Prostate cancer is the most popular genital adenocarcinoma and the second leading cause of death in male carcinoma patients. Although 18F-FDG positron emission tomography (PET) has been widely used for localization and staging of many cancers, its utility for detection of the local recurrent prostate cancer is limited by excretory FDG activity in the urinary bladder. So, it is worthwhile to develop additional new PET probes when the utility of currently available probes are limited. Copper is one of the major essential metal nutrients in mammals, and notably used as positron emitters in well-established PET imaging due to the major advantages of PET over past decades. Considering about the availability and production cost, the research efforts in copper radiopharmaceuticals are mainly focused on the use of 64Cu (T1/2=12.7h, beta+ 17.4%，beta- 39%，Ec 43%）, a radioisotope with low positron energy (E+max=0.656 MeV) which is ideal for PET imaging quantification. In current biomedical application of PET tracers, copper is mainly designed as cryptate complex for rendering the metal complex with desired stability. However, interestingly, 64CuS nanoparticle was recently reported as probe to imaging glioma cancer xenograft, which may present a new direction for the copper radiopharmaceutical application. Based on past research evidences, we hypothesize the 64CuS nanoparticles has similar targeting and imaging capability to prostate tumor sites but better stability than 64CuCl2 for in vivo delivery. To minimize the non-specific composition by copper metabolic organs and improve the assemblage quantity, polyethylene glycol linked with modified analogue of bombesin peptide, a typical prostate cancer homing peptide, would be prepared for coating these nanoparticles for quick targeted delivery to prostate lesion. This tumor targeting nano-tracer would be developed and its potential for PET imaging application in recurrent prostate cancer diagnostic would be evaluated in this project.

前列腺肿瘤靠近膀胱等葡萄糖代谢器官，因此临床常用的FDG造影剂用于PET显像鉴别前列腺肿瘤病灶较为困难。铜64（64Cu，T1/2=12.7h）由于其半衰期适中，在盆腔区域背景造影低，生物安全性高，近年来已成为国内外备受关注的新型PET显像用放射性核素。申请人前期研究结果显示，64CuCl2单独用于前列腺肿瘤显像时靶向性差，进入肿瘤细胞时间较长，难以满足临床需求。本课题针对上述缺点，拟制备出化学性质稳定，生物安全性较高，具有良好细胞穿透能力，且易于标记的64CuS纳米微粒作为肿瘤显像分子；选用自行设计的，能与前列腺癌标志物GRPR受体结合的多肽Bom作为肿瘤靶向载体，将二者结合，开发一类具有特异性结合并进入前列腺癌细胞能力的铜64硫化铜-多肽复合纳米微粒，研究其用于前列腺肿瘤PET显像诊断的可行性。

近年来CuS纳米颗粒作为新一代肿瘤近红外治疗分子在皮下荷瘤动物模型研究中取得了良好的效果并受到了科研者的关注，但CuS本身只能依赖ERP被动靶向效应到达肿瘤部位，肿瘤靶向效率较低，且过往研究均集中在皮下荷瘤模型中，没有在原位肿瘤中进行。本研究成功研制出了一种针对前列腺癌的多肽复合纳米颗粒，以蛙皮素肽Bombesin为肿瘤靶向分子，铜-64（64CuS）作为放射性正电子显像分子，靶向至前列腺癌标志物GRPR，验证了此纳米颗粒用于小动物原位前列腺癌的诊断显像可行性。研究结果证实，在体外细胞试验中，我们的64CuS-Bom复合纳米颗粒与前列腺癌细胞的特异性结合时间更短，结合效率更高：普通CuS纳米颗粒的1h结合率仅为±9.20±0.84%，而我们的复合纳米颗粒与前列腺癌细胞的结合率可达48.15±6.04%，且在6h内可进一步上升至73.84±3.64%，远高于普通CuS纳米颗粒14.74±0.64%；进一步的小动物原位前列腺癌体内显像结果显示，64CuS-Bom复合纳米颗粒1h内开始富集至原位前列腺癌部位，药物注射后6h可达到良好诊断显影的效果，肿瘤感兴趣区域（ROI）的ID%/g=4.7±0.56，远高于单独CuS纳米颗粒（ID%/g=1.1±0.51）。上述研究结果证实了我们设计的复合纳米颗粒具有良好的体内外肿瘤靶向性，特别是能在原位前列腺癌模型上成功应用，为进一步前列腺癌靶向治疗奠定了基础；此外，我们在原位肿瘤模型和皮下荷瘤模型上的结果差异，对目前纳米颗粒的动物研究模型选择具有重要影响。