Development of sensitive contrast agents for positive magnetic resonance (MR) imaging of biosystems still remains a great challenge. Herein, we report a facile process to construct hybrid alginate (AG) nanogels (NGs) loaded with manganese oxide (Mn₃O₄) nanoparticles (NPs) for enhanced tumor MR imaging. The obtained AG/PEI-Mn₃O₄ NGs with a mean size of 141.6 nm display excellent colloidal stability in aqueous solution and good cytocompatibility in the studied concentration range. Moreover, the hybrid NGs have a high r₁ relaxivity of 26.12 mM^–1 s^–1, which is about 19.5 times higher than that of PEI-Mn₃O₄ NPs with PEI surface amine acetylated (PEI.Ac–Mn₃O₄ NPs). Furthermore, the AG/PEI-Mn₃O₄ NGs presented longer blood circulation time and better tumor MR imaging performances in vivo than PEI.Ac–Mn₃O₄ NPs. With the good biosafety confirmed by histological examinations, the developed AG/PEI-Mn₃O₄ NGs may be potentially used as an efficient contrast agent for enhanced MR imaging of different biosystems.

中文翻译：

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构建负载氧化锰纳米颗粒的混合海藻酸盐纳米凝胶用于增强肿瘤磁共振成像

开发用于生物系统正磁共振 (MR) 成像的敏感造影剂仍然是一个巨大的挑战。_{在此，我们报告了一种简便的方法来构建负载有氧化锰 (Mn 3} O ₄ ) 纳米粒子 (NPs) 的混合藻酸盐 (AG) 纳米凝胶 (NGs)，以增强肿瘤 MR 成像。所获得的平均粒径为141.6 nm的AG/PEI-Mn ₃ O ₄ NGs在水溶液中表现出优异的胶体稳定性，在所研究的浓度范围内具有良好的细胞相容性。此外，杂化 NGs 具有26.12 mM ^–1 s ^–1的高r _{1弛豫率，是 PEI-Mn 3} O ₄的 19.5 倍。具有 PE​​I 表面胺乙酰化的 NPs (PEI.Ac–Mn ₃ O ₄ NPs)。此外，AG/PEI-Mn ₃ O ₄ NGs比PEI.Ac-Mn ₃ O ₄ NPs具有更长的血液循环时间和更好的体内肿瘤MR成像性能。由于组织学检查证实了良好的生物安全性，所开发的 AG/PEI-Mn ₃ O ₄ NGs 可潜在地用作增强不同生物系统 MR 成像的有效造影剂。