Ultrahigh relaxivity and safe probes of manganese oxide nanoparticles for in vivo imaging.

Mn-based nanoparticles (NPs) have emerged as new class of probes for magnetic resonance imaging due to the impressive contrast ability. However, the reported Mn-based NPs possess low relaxivity and there are no immunotoxicity data regarding Mn-based NPs as contrast agents. Here, we demonstrate the ultrahigh relaxivity of water protons of 8.26 mM−1s−1 from the Mn3O4 NPs synthesized by a simple and green technique, which is twice higher than that of commercial gadolinium (Gd)-based contrast agents (4.11 mM−1s−1) and the highest value reported to date for Mn-based NPs. We for the first time demonstrate these Mn3O4 NPs biocompatibilities both in vitro and in vivo are satisfactory based on systematical studies of the intrinsic toxicity including cell viability of human nasopharyngeal carcinoma cells, normal nasopharyngeal epithelium, apoptosis in cells and in vivo immunotoxicity. These findings pave the way for the practical clinical diagnosis of Mn based NPs as safe probes for in vivo imaging.

基于锰的纳米粒子（NPs）由于其出色的造影能力，已成为一类新型的磁共振成像探针。然而，已报道的基于锰的纳米粒子弛豫率较低，且没有关于其作为造影剂的免疫毒性数据。在此，我们通过一种简单的绿色技术合成了四氧化三锰纳米粒子，其水质子的弛豫率超高，达到8.26 mM⁻¹s⁻¹，比市售的基于钆（Gd）的造影剂（4.11 mM⁻¹s⁻¹）高出一倍，也是迄今为止基于锰的纳米粒子所报道的最高值。我们首次通过对内在毒性进行系统研究，包括人鼻咽癌、正常鼻咽上皮细胞的活力、细胞凋亡以及体内免疫毒性，证明这些四氧化三锰纳米粒子在体外和体内的生物相容性均令人满意。这些发现为基于锰的纳米粒子作为体内成像的安全探针在临床实际诊断中的应用铺平了道路。