Department of Pharmaceutical Engineering, School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, 122 Luoshi Road, Wuhan, Hubei 430070, China.
Department of Radiology, Center for Molecular Imaging, University of Michigan, Ann Arbor, MI 48109-2200, United States; College of Animal Sciences and Veterinary Medicine, Henan Agriculture University, Zhengzhou, Henan 450002, China.
Acta Biomater. 2018 Oct 1;79:306-316. doi: 10.1016/j.actbio.2018.08.036. Epub 2018 Aug 29.
Unimolecular micelles based on hyperbranched polyamidoamine (PAMAM) dendrimer were synthesized as both a cargo delivery vector and an imaging agent for triple-negative breast tumors, and the chemical synthesis procedures are detailed in this study. With the chemical conjugation of a peptide (F3, against cellular nucleolin) to increase its cellular internalization, these micelles can accumulate potently and specifically in breast cancer cells (e.g., MDA-MB-231). The size and morphology of these PAMAM-based micelles have been measured by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The hydrazone bond (responsive to pH alteration) between the loaded doxorubicin (DOX, as a model drug here) and PAMAM micelles enables cargo release following pH changes. Flow cytometry and confocal fluorescence microscopy revealed that PAMAM micelles with F3 attachment (PAMAM-DOX-F3) had stronger internalization into MDA-MB-231 cells (nucleolin-positive) than PAMAM micelles without F3 conjugation (PAMAM-DOX), whereas both of them have minimal interactions with L929 fibroblasts (nucleolin-negative). The positron-emitting isotope Cu was added into PAMAM micelles by chelation to track their pharmacokinetic behavior (organ distribution profile) in vivo by positron emission tomography (PET) imaging. Serial PET imaging demonstrated that the accumulation of Cu-PAMAM-DOX-F3 in MDA-MB-231 tumors was fast, potent, and persistent (tumor uptake: 6.1 ± 1.2% injection dose per gram [%ID/g] at 24 h p.i.), significantly higher than that of Cu-PAMAM-DOX (2.5 ± 0.4%ID/g at the same time). Their distribution profiles in other organs/tissues were quite similar, with a relatively short circulation time. In addition, ex vivo fluorescence imaging confirmed that DOX can be delivered efficiently by these PAMAM micelles to MDA-MB-231 tumors. Deducing from these data, we believe that PAMAM-based micelles can be useful for selective combinational treatment of cancer.
Micelles are a very useful biomaterial for theranostic purposes, and one of the major hurdles for micelles (particularly those from self-assembling) is their relatively low stability, especially when administered in vivo. In this study, we have attempted to overcome this limitation by designing unimolecular micelles (based on the concept of "one micelle is composed of one macromolecule") from polyamidoamine (PAMAM) dendrimers, in which the drug cargos (e.g., doxorubicin) are chemically attached to PAMAM through a hydrazone bond; hence, they can be used as a tumor-selective diagnostic/therapeutic platform. These unimolecular micelles possess superior stability compared to conventional micelles and can undertake stimulus (pH)-responsive cargo release for more "targeted" cancer therapy. With the incorporation of a tumor-targeting peptide sequence (F3) and a positron-emitting isotope (copper-64), the pharmacokinetic behavior of these micelles can be readily monitored by positron emission tomography imaging technique to confirm their specificity against cancer tissues. With further optimization, this micellar platform can have a broad clinical applicability owing to its biocompatibility, selectivity, and stability.
合成基于超支化聚酰胺胺（PAMAM）树状大分子的单分子胶束，用作三阴性乳腺癌的载药载体和成像剂，并详细描述了其化学合成过程。通过与肽（F3，针对细胞核仁素）的化学偶联来增加其细胞内化作用，这些胶束可以在乳腺癌细胞（如 MDA-MB-231）中强烈且特异性地聚集。通过透射电子显微镜（TEM）和动态光散射（DLS）测量了这些基于 PAMAM 的胶束的大小和形态。载药阿霉素（DOX，作为模型药物）与 PAMAM 胶束之间的腙键（对 pH 变化敏感）可在 pH 变化后实现货物释放。流式细胞术和共聚焦荧光显微镜显示，与未连接 F3 的 PAMAM 胶束（PAMAM-DOX）相比，连接 F3 的 PAMAM 胶束（PAMAM-DOX-F3）具有更强的 MDA-MB-231 细胞内化作用（核仁素阳性），而它们与 L929 成纤维细胞（核仁素阴性）的相互作用都最小。将放射性同位素铜通过螯合作用添加到 PAMAM 胶束中，通过正电子发射断层扫描（PET）成像技术在体内追踪其药代动力学行为（器官分布谱）。连续的 PET 成像显示，Cu-PAMAM-DOX-F3 在 MDA-MB-231 肿瘤中的积累速度快、强度高且持久（24 h 时肿瘤摄取：6.1±1.2%注入剂量/克[ID/g]），明显高于 Cu-PAMAM-DOX（相同时间内 2.5±0.4%ID/g）。它们在其他器官/组织中的分布谱非常相似，循环时间相对较短。此外，离体荧光成像证实，这些 PAMAM 胶束可以有效地将 DOX 递送至 MDA-MB-231 肿瘤。根据这些数据，我们认为基于 PAMAM 的胶束可用于癌症的选择性联合治疗。
胶束是用于治疗诊断目的的非常有用的生物材料，胶束（特别是自组装胶束）的主要障碍之一是其相对较低的稳定性，尤其是在体内给药时。在这项研究中，我们试图通过设计基于聚酰胺胺（PAMAM）树状大分子的单分子胶束（基于“一个胶束由一个大分子组成”的概念）来克服这一限制，其中药物载体（如阿霉素）通过腙键化学连接到 PAMAM 上；因此，它们可以用作肿瘤选择性诊断/治疗平台。与传统胶束相比，这些单分子胶束具有更高的稳定性，并且可以进行刺激（pH）响应的货物释放，以实现更“靶向”的癌症治疗。通过掺入肿瘤靶向肽序列（F3）和正电子发射同位素（铜-64），可以通过正电子发射断层扫描成像技术轻松监测这些胶束的药代动力学行为，以确认其对癌症组织的特异性。通过进一步优化，由于其生物相容性、选择性和稳定性，该胶束平台具有广泛的临床应用前景。
