Department of Radiology, Taipei City Hospital, Taipei, Taiwan; Department of Radiology, School of Medicine, National Taiwan University, Taipei, Taiwan.
Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.
Biomaterials. 2015;53:699-708. doi: 10.1016/j.biomaterials.2015.02.122. Epub 2015 Mar 25.
In this study, we aimed to validate the feasibility of receptor-targeted tumor theranostics with folate-conjugated (FA) and camptothecin-loaded (CPT) acoustic nanodroplets (NDs) (collectively termed FA-CPT-NDs). The ND formulation was based on lipid-stabilized low-boiling perfluorocarbon that can undergo acoustic droplet vaporization (ADV) under ultrasound (US) exposure. Conjugation of folate enhanced the selective delivery to tumors expressing high levels of folate receptor (FR) under mediation by the enhanced permeability and retention effect. In vitro and in vivo studies were performed using FR-positive KB and FR-negative HT-1080 cell lines and mouse xenograft tumor models. Simultaneous therapy and imaging were conducted with a clinical US imaging system at mechanical indices of up to 1.4 at a center frequency of 10 MHz. The results demonstrated that FA-CPT-NDs selectively attached to KB cells, but not HT-1080 cells. The targeted ADV caused instant and delayed damage via mechanical disruption and chemical toxicity to decrease the viability of KB cells by up to 45%, a much higher decrease than that achieved by the NDs without folate conjugation. The in vivo experiments showed that FR-mediated targeting successfully enhanced the EPR of FA-CPT-NDs in KB tumors mainly on the tumor periphery as indicated by immunofluorescence microscopy and US B-mode imaging. Treatments with FA-CPT-NDs at a CPT dose of 50 μg/kg inhibited the growth of KB tumors for up to six weeks, whereas treatment with NDs lacking folate produced a 4.6-fold increase in tumor volume. For HT-1080 tumors, neither the treatments with FA-CPT-NDs nor those with the NDs lacking folate presented tumor growth inhibition. In summary, FR-targeted tumor theranostics has been successfully implemented with FA-CPT-NDs and a clinical US unit. The ligand-directed and EPR-mediated accumulation provides active and passive targeting capabilities, permitting the antitumor effects of FA-CPT-NDs to be exerted selectively to FR-positive tumors and simultaneously providing targeted US imaging capabilities.
在这项研究中，我们旨在验证叶酸偶联（FA）和喜树碱负载（CPT）声纳米液滴（NDs）（统称为 FA-CPT-NDs）的受体靶向肿瘤治疗的可行性。ND 制剂基于脂质稳定的低沸点全氟碳，可在超声（US）暴露下发生声致液滴汽化（ADV）。叶酸的偶联通过增强通透性和保留效应介导，增强了对表达高水平叶酸受体（FR）的肿瘤的选择性递送。使用 FR 阳性 KB 和 FR 阴性 HT-1080 细胞系以及小鼠异种移植肿瘤模型进行了体外和体内研究。使用临床 US 成像系统在高达 1.4 的机械指数和 10 MHz 的中心频率下进行了联合治疗和成像。结果表明，FA-CPT-NDs 选择性地附着在 KB 细胞上，但不附着在 HT-1080 细胞上。靶向 ADV 通过机械破坏和化学毒性引起即时和延迟损伤，使 KB 细胞的活力降低多达 45%，这比没有叶酸偶联的 ND 降低得更多。体内实验表明，FR 介导的靶向成功增强了 FA-CPT-NDs 在 KB 肿瘤中的 EPR，这主要是通过免疫荧光显微镜和 US B 模式成像在外周肿瘤中观察到的。以 50 μg/kg 的 CPT 剂量用 FA-CPT-NDs 治疗可抑制 KB 肿瘤的生长长达六周，而用缺乏叶酸的 ND 治疗可使肿瘤体积增加 4.6 倍。对于 HT-1080 肿瘤，FA-CPT-NDs 或缺乏叶酸的 ND 的治疗均未抑制肿瘤生长。总之，已成功使用 FA-CPT-NDs 和临床 US 单元实施了 FR 靶向肿瘤治疗。配体定向和 EPR 介导的积累提供了主动和被动靶向能力，使 FA-CPT-NDs 的抗肿瘤作用能够选择性地作用于 FR 阳性肿瘤，并同时提供靶向 US 成像能力。
