Magnetic resonance imaging (MRI) relies on appropriate contrast agents, especially for visualizing transplanted cells within host tissue. In recent years, compounds containing fluorine-19 have gained significant attention as MRI probe, particularly in dual 1H/19F-MR imaging. However, various factors affecting probe sensitivity, such as fluorine content and the equivalency of fluorine atoms, must be considered. In this study, we synthesized fluorinated micelles with adjustable surface positive charge density and investigated their physicochemical properties and MRI efficacy in phantoms and labeled cells. While the micelles exhibited clear signals in 19F-MR spectra and imaging, the concentrations required for MRI visualization of labeled cells were relatively high, adversely affecting cell viability. Despite their favourable physicochemical properties, achieving higher labeling rates without compromising cell viability during labeling remains a challenge for potential in vivo applications.

• Keywords
• 19F magnetic resonance imaging, 19F magnetic resonance spectroscopy, Cell labeling, Fluorinated micelles,
• MeSH
• Staining and Labeling methods   MeSH
• Phantoms, Imaging MeSH
• Fluorine chemistry   MeSH
• Halogenation MeSH
• Cations * chemistry   MeSH
• Contrast Media chemistry   MeSH
• Humans MeSH
• Magnetic Resonance Imaging methods   MeSH
• Micelles * MeSH
• Mice MeSH
• Cell Survival * drug effects   MeSH
• Fluorine-19 Magnetic Resonance Imaging methods   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Fluorine MeSH
• Cations * MeSH
• Contrast Media MeSH
• Micelles * MeSH

PURPOSE: Combining specific and quantitative F-19 magnetic resonance imaging (MRI) with sensitive and convenient optical imaging provides complementary information about the distribution and viability of transplanted pancreatic islet grafts. In this study, pancreatic islets (PIs) were labeled with positively charged multimodal nanoparticles based on poly(lactic-co-glycolic acid) (PLGA-NPs) with encapsulated perfluoro-15-crown-5-ether and the near-infrared fluorescent dye indocyanine green. PROCEDURES: One thousand and three thousand bioluminescent PIs were transplanted into subcutaneous artificial scaffolds, which served as an alternative transplant site. The grafts were monitored using in vivo F-19 MR, fluorescence, and bioluminescence imaging in healthy rats for 2 weeks. RESULTS: Transplanted PIs were unambiguously localized in the scaffolds by F-19 MRI throughout the whole experiment. Fluorescence was detected in the first 4 days after transplantation only. Importantly, in vivo bioluminescence correlated with the F-19 MRI signal. CONCLUSIONS: We developed a trimodal imaging platform for in vivo examination of transplanted PIs. Fluorescence imaging revealed instability of the fluorescent dye and its limited applicability for longitudinal in vivo studies. A correlation between the bioluminescence signal and the F-19 MRI signal indicated the fast clearance of PLGA-NPs from the transplantation site after cell death, which addresses a major issue with intracellular imaging labels. Therefore, the proposed PLGA-NP platform is reliable for reflecting the status of transplanted PIs in vivo.

• Keywords
• F-19 magnetic resonance imaging, Nanoparticles, Optical imaging, Pancreatic islets, Transplantation,
• MeSH
• Endocytosis MeSH
• Fluorine chemistry   MeSH
• Fluorescence MeSH
• Islets of Langerhans diagnostic imaging   MeSH
• Luminescent Measurements * MeSH
• Magnetic Resonance Imaging * MeSH
• Models, Animal MeSH
• Molecular Imaging * MeSH
• Rats, Inbred Lew MeSH
• Rats, Transgenic MeSH
• Tissue Survival MeSH
• Tissue Scaffolds chemistry   MeSH
• Islets of Langerhans Transplantation * MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Fluorine MeSH