Biocompatible core–shell Fe₃O₄@[email protected]₂ nanoparticles (named as FOCMO NPs) with an average size at 130 nm prepared through an effortless yet efficient strategy were employed as pH-activatable T₁-T₂* dual-modality magnetic resonance imaging (MRI) contrast agents (CAs). The release rate of Mn ions in acidic PBS (pH = 5.0) was approximately 10 times to that under condition with pH value of 7.4. Benefiting from excellent acid responsiveness, which facilitates the release of ions from FOCMO NPs at tumor region with acidic microenvironment and organelles, the diagnosis accuracy was commendably improved. After intravenous injection of FOCMO NPs, an efficiently intensive contrast in tumors are realized with a distinct enhancement of 127% in T₁ MRI signal 24 h after the administration. Moreover, a significant decreasement of 71% is witnessed in T₂ MRI signal. Those demonstrated that FOCMO NPs can achieve the purpose of positive/negative MRI simultaneously. Furthermore, obtained FOCMO NPs showed great hemocompatibility and negligible toxicity.

中文翻译：

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核-壳结构化的Fe ₃ O ₄ @ [受电子邮件保护] ₂纳米颗粒，具有pH响应性T ₁ -T ₂ *用于肿瘤诊断的双峰造影剂

pH活化T ₁ -T ₂采用具有生物相容性的核壳Fe ₃ O ₄ @ [受电子邮件保护] ₂纳米粒子（称为FOCMO NPs），该纳米粒子通过毫不费力却有效的策略制备，平均粒径为130 nm。*双模态磁共振成像（MRI）造影剂（CAs）。在酸性PBS（pH = 5.0）中，Mn离子的释放速率约为pH值为7.4时的10倍。得益于出色的酸反应性，该反应促进了带有酸性微环境和细胞器的FOCMO NPs在肿瘤区域的离子释放，诊断准确性得到了可喜的提高。静脉注射FOCMO NP后，在给药后24小时，T ₁ MRI信号明显增强了127％，从而在肿瘤中实现了有效的强烈对比。此外，在T _2中见证了71％的显着下降MRI信号。那些证明了FOCMO NP可以同时实现正/负MRI的目的。此外，获得的FOCMO NPs具有很好的血液相容性和可忽略的毒性。