64Cu-Labeled Folate-Conjugated Shell Cross-Linked Nanoparticles for Tumor Imaging and Radiotherapy: Synthesis, Radiolabeling, and Biologic Evaluation

Journal of Nuclear Medicine

Jeffrey L. Turner¹  Xiankai Sun¹  Kai Qi¹  Raffaella Rossin¹  Dipanjan Pan¹  Karen L. Wooley¹  Michael J. Welch¹ 

关键词: ⁶⁴Cu;    folate-nanoparticles;    radiolabeling;    folate receptor;    enhanced permeability and retention effect;   

DOI  :  

学科分类：医学（综合）

来源: Society of Nuclear Medicine

【 摘 要 】

Long-circulating nanoparticles functionalized with ligands for receptors overexpressed by tumor cells have promising applications for active and passive tumor targeting. The purpose of this study was to evaluate 64Cu-radiolabeled folate-conjugated shell cross-linked nanoparticles (SCKs) as candidate agents to shuttle radionuclides and drugs into tumors overexpressing the folate receptor (FR). Methods: SCKs were obtained by cross-linking the shell of micelles obtained from amphiphilic diblock copolymers. SCKs were then functionalized with folate, fluorescein thiosemicarbazide (FTSC), and 1,4,8,11-tetraazacyclotetradecane-N,N′,N″,N‴-tetraacetic acid (TETA). The specific interaction of SCK-folate with the FR was investigated on KB cells. The biodistributions of 64Cu-TETA-SCK and 64Cu-TETA-SCK-folate were evaluated in athymic mice bearing small-size KB cell xenografts (10–100 mg), whereas the intratumor distributions were investigated by autoradiography in 0.3- to 0.6-g KB cell xenografts. Results: A global solution-state functionalization strategy has been introduced for attaching optimum numbers of targeting and imaging agents onto the SCKs for increasing the efficiency of interaction with cell-surface receptors. Epifluorescence microscopy confirmed the specific interaction of FTSC-SCK-folate with the FR in vitro. 64Cu labeling of TETA-SCKs led to the radiolabeled compounds with 15%–20% yield and >95% radiochemical purity. The biodistribution results demonstrated high accumulation of 64Cu-labeled SCKs in organs of the reticuloendothelial system (RES) (56.0 ± 7.1 %ID/g and 45.7 ± 3.5 %ID/g [percentage injected dose per gram] in liver at 10 min after injection for folated and nonfolated SCKs, respectively) and a prolonged blood circulation. No increase of SCK tumor uptake deriving from folate conjugation was observed (5.9 ± 2.8 %ID/g and 6.0 ± 1.9 %ID/g at 4 h after injection for folated and nonfolated SCKs, respectively). However, tumor accumulation was higher in small-size tumors, where competitive block of SCK-folate uptake with excess folate was observed. Autoradiography results confirmed the extravasation of radiolabeled SCKs in vascularized areas of the tumor, whereas no diffusion was observed in necrotic regions. Conclusion: Despite high RES uptake, the evaluated 64Cu-labeled SCKs exhibited long circulation in blood and were able to passively accumulate in tumors. Furthermore, SCK-folate uptake was competitively blocked by excess folate in small-size solid tumors, suggesting interaction with the FR. For these reasons, functionalized SCKs are promising drug-delivery agents for imaging and therapy of early-stage solid tumors.

【 授权许可】

Unknown