Integrated magnetic resonance and optical imaging to create dynamically dual-modality imaging to observe the biological process of endothelial progenitor cells (EPCs) homing to the local vascular endothelial injury after transplanted.

Chemically synthesized PEG-PEI nanocarriers loaded with magnetic resonance imaging agent SPIO and near-infrared dye Cy7.5 were randomly divided into an empty carrier control group (PEG-PEI group) and an experimental group (PEG-PEI-SPIO group) ; The particle size and potential of the nanoparticles were measured by dynamic light scattering experiment in vitro, CCK-8 experiment and Annexin V flow cytometry; A nude rat carotid artery intima injury model was established, and the tail vein of EPCs was dynamically observed by magnetic resonance imaging and intravital fluorescence imaging After transplantation, the process of homing to the local vascular endothelial injury is targeted. t test was used for comparison between two groups.

Dynamic light scattering experiments show that the particle size of PEG-PEI-SPIO nanoparticles is 129.6 nm, and the surface potential is 2.4 mV when N/P = 12; electron microscopy Results show that the composite nanoparticles has circles shape, SPIO is located in the center of the composite system, and the particle size of the composite system is about 130 nm; CCK- 8 experiment and Annexin V flow cytometry experiment show that when N/P = 12, compared to the nanocarrier PEG-PEI control group, the proliferation toxicity and apoptosis toxicity of PEG-PEI-SPIO nanocarriers has no statistic differences; Prussian blue staining shows that PEG-PEI-SPIO nanoparticles can be endothelialized into the cytoplasm. In vivo fluorescence imaging Results showed that Cy7.5-labeled EPCs home to the vascular endothelial injury within 2 days after transplantation (increased fluorescence signal intensity) ; MRI Results showed that SPIO-labeled EPCs reached the sub-endothelium injury location within 2 days after transplantation (the intensity of MRI T₂ decreased) .

PEG-PEI nanocarrier can effectively integrate the advantages of magnetic resonance imaging and optical imaging in terms of spatial resolution, sensitivity, specificity, and quantitative analysis. Tracking of EPCs' targeted homing process with nanocarrier can be used for the in vivo evaluation of transplantation effect and optimizing transplantation strategy, which provides objective indicators and theoretical guidance for stem cell therapy.