(164aa) Human Forebrain Organoid-Derived Extracellular Vesicle Labelling with Iron Oxides for in Vitro Magnetic Resonance Imaging

The significant roles of extracellular vesicles (EVs) as intracellular mediators, disease biomarkers, and therapeutic agents, make them as a scientific hotspot. In particular, EVs secreted by human stem cells show significance in treating neurological disorders such as Alzheimer’s disease and ischemic stroke. However, the clinical applications of EVs are limited due to their poor targeting capabilities and low therapeutic efficacies after intravenous administration. Superparamagnetic iron oxide (SPIO) nanoparticles are biocompatible and have been shown to improve the targeting ability of EVs. In particular, ultrasmall SPIO (USPIO, <50 nm) is more suitable for labelling nanoscale EVs due to its small size. In this study, induced forebrain neural progenitor cortical organoids (iNPCo) were differentiated from human induced pluripotent stem cells (iPSCs), and the iNPCo expressed FOXG1, Nkx2.1, α-catenin, as well as β-tubulin III. EVs were isolated from iNPCo media, then were loaded with USPIOs by sonication for 30 seconds, followed by incubation at 37℃ for one hour. Size and concentration of EV particles were measured by nanoparticle tracking analysis, and no significant changes were observed before and after sonication. miR-155 and miR-221 were decreased after sonication. In vitro magnetic resonance imaging (MRI) revealed the contrast of USPIOs labeled EVs while the unlabeled EVs did not have the contrast. Besides, the labeled EVs showed shorter T1, T2, T2* echo times compared with the gel, while the unlabeled EVs showed longer echo times. Our study demonstrated that USPIO labeling was a feasible approach for in vitro tracking of EVs, which paves the way for further in vivo examination.