Yin Jie, Yin Guangfu, Pu Ximing, Huang Zhongbing, Yao Dajin
College of Materials Science and Engineering, Sichuan University No. 24, South 1st Section, 1st Ring Road Chengdu 610065 PR China
School of Automation and Information Engineering, Sichuan University of Science and Engineering Zigong 643000 PR China.
RSC Adv. 2019 Jun 20;9(34):19397-19407. doi: 10.1039/c9ra02636c. eCollection 2019 Jun 19.
As desirable contrast agents for magnetic resonance imaging (MRI), ultrasmall superparamagnetic iron oxides (USPIOs) are required to exhibit both low cytotoxicity and specific targetability besides superparamagnetism to achieve better imaging contrast at lower dose, and cladding with biocompatible polymers and modification with targeting ligands are considered to be the most effective strategies. In this study, novel dextran wrapped and peptide WSGPGVWGASVK (peptide-WSG) grafted USPIOs were meticulously prepared and systematically characterized. Firstly, dextran (Dex) cladded USPIOs (USPIOs@Dex) were synthesized with a well-designed co-precipitation procedure in which the biocompatible dextran played dual roles of grain inhibitor and cladding agent. After that, sodium citrate was applied to carboxylize the hydroxyls of the dextran molecules an esterification reaction, and then tumor targeting peptide-WSG was grafted to the carboxyl groups by the EDC method. The XRD, TEM, and FTIR results showed that inverse spinel structure FeO crystallites were nucleated and grown in aqueous solution, and the catenulate dextran molecules gradually bound on their surface, meanwhile the growth of grains was inhibited. The size of original crystallite grains was about 7 nm, but the mean size of USPIOs@Dex aggregates was 165.20 nm. After surface modification by sodium citrate and peptide-WSG with ultrasonic agitation, the size of the USPIOs@Dex-WSG aggregates was smaller (66.06 nm) because the hydrophilicity was improved, so USPIOs@Dex-WSG could evade being eliminated by RES more easily, and prolong residence time in blood circulation. The VSM and T-weighted MRI results showed that USPIOs@Dex-WSG were superparamagnetic with a saturation magnetization of 44.65 emu g, and with high transverse relaxivity as the relaxivity coefficient value was 229.70 mM s. The results of MTT assays and the Prussian blue staining revealed that USPIOs@Dex-WSG exhibited nontoxicity for normal cells such as L929 and HUVECs, and were specifically targeted to the SKOV-3 cells. Thus, the novel dextran wrapped and WSG-peptide grafted USPIOs have potential to be applied as tumor active targeting contrast agents for MRI.
作为磁共振成像（MRI）理想的造影剂，除了超顺磁性外，超小超顺磁性氧化铁（USPIOs）还需要表现出低细胞毒性和特异性靶向性，以便在较低剂量下实现更好的成像对比度，而用生物相容性聚合物包覆和用靶向配体修饰被认为是最有效的策略。在本研究中，精心制备并系统表征了新型葡聚糖包裹且肽WSGPGVWGASVK（肽-WSG）接枝的USPIOs。首先，采用精心设计的共沉淀法合成了葡聚糖（Dex）包覆的USPIOs（USPIOs@Dex），其中生物相容性葡聚糖起到了晶粒抑制剂和包覆剂的双重作用。之后，通过酯化反应使用柠檬酸钠将葡聚糖分子的羟基羧基化，然后通过EDC法将肿瘤靶向肽-WSG接枝到羧基上。XRD、TEM和FTIR结果表明，反尖晶石结构的FeO微晶在水溶液中形核并生长，链状葡聚糖分子逐渐结合在其表面，同时晶粒生长受到抑制。原始微晶颗粒的尺寸约为7nm，但USPIOs@Dex聚集体的平均尺寸为165.20nm。经柠檬酸钠和肽-WSG超声搅拌表面修饰后，USPIOs@Dex-WSG聚集体的尺寸更小（66.06nm），因为亲水性得到了改善，所以USPIOs@Dex-WSG能够更轻松地逃避被RES清除，并延长在血液循环中的停留时间。VSM和T加权MRI结果表明，USPIOs@Dex-WSG具有超顺磁性，饱和磁化强度为44.65emu g，横向弛豫率高，弛豫率系数值为229.70mM s。MTT试验和普鲁士蓝染色结果表明，USPIOs@Dex-WSG对L929和HUVECs等正常细胞无毒，且能特异性靶向SKOV-3细胞。因此，新型葡聚糖包裹且WSG-肽接枝的USPIOs有潜力作为MRI的肿瘤活性靶向造影剂应用。
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