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.

• Klíčová slova
• 19F magnetic resonance imaging, 19F magnetic resonance spectroscopy, Cell labeling, Fluorinated micelles,
• MeSH
• barvení a značení metody   MeSH
• fantomy radiodiagnostické MeSH
• fluor chemie   MeSH
• halogenace MeSH
• kationty * chemie   MeSH
• kontrastní látky chemie   MeSH
• lidé MeSH
• magnetická rezonanční tomografie metody   MeSH
• micely * MeSH
• myši MeSH
• viabilita buněk * účinky léků   MeSH
• zobrazování fluorovou magnetickou rezonancí metody   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fluor MeSH
• kationty * MeSH
• kontrastní látky MeSH
• micely * MeSH

19F magnetic resonance imaging (MRI) using fluoropolymer tracers has recently emerged as a promising, non-invasive diagnostic tool in modern medicine. However, despite its potential, 19F MRI remains overlooked and underused due to the limited availability or unfavorable properties of fluorinated tracers. Herein, we report a straightforward synthetic route to highly fluorinated 19F MRI nanotracers via aqueous dispersion polymerization-induced self-assembly of a water-soluble fluorinated monomer. A polyethylene glycol-based macromolecular chain-transfer agent was extended by RAFT-mediated N-(2,2,2-trifluoroethyl)acrylamide (TFEAM) polymerization in water, providing fluorine-rich self-assembled nanoparticles in a single step. The resulting nanoparticles had different morphologies and sizes ranging from 60 to 220 nm. After optimizing their structure to maximize the magnetic relaxation of the fluorinated core, we obtained a strong 19F NMR/MRI signal in an aqueous environment. Their non-toxicity was confirmed on primary human dermal fibroblasts. Moreover, we visualized the nanoparticles by 19F MRI, both in vitro (in aqueous phantoms) and in vivo (after subcutaneous injection in mice), thus confirming their biomedical potential.

• MeSH
• akrylamid MeSH
• lidé MeSH
• magnetická rezonanční tomografie metody   MeSH
• myši MeSH
• nanočástice * chemie   MeSH
• polymerizace MeSH
• voda * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• akrylamid MeSH
• voda * MeSH

Upconverting nanoparticles are attracting extensive interest as a multimodal imaging tool. In this work, we report on the synthesis and characterization of gadolinium-enriched upconverting nanoparticles for bimodal magnetic resonance and optical luminescence imaging. NaYF4:Gd3+,Yb3+,Tm3+ core upconverting nanoparticles were obtained by a thermal coprecipitation of lanthanide oleate precursors in the presence of oleic acid as a stabilizer. With the aim of improving the upconversion emission and increasing the amount of Gd3+ ions on the nanoparticle surface, a 2.5 nm NaGdF4 shell was grown by the epitaxial layer-by-layer strategy, resulting in the 26 nm core-shell nanoparticles. Both core and core-shell nanoparticles were coated with poly(ethylene glycol) (PEG)-neridronate (PEG-Ner) to have stable and well-dispersed upconverting nanoparticles in a biological medium. FTIR spectroscopy and thermogravimetric analysis indicated the presence of ∼20 wt % of PEG-Ner on the nanoparticle surface. The addition of inert NaGdF4 shell resulted in a total 26-fold enhancement of the emission under 980 nm excitation and also affected the T 1 and T 2 relaxation times. Both r 1 and r 2 relaxivities of PEG-Ner-modified nanoparticles were much higher compared to those of non-PEGylated particles, thus manifesting their potential as a diagnostic tool for magnetic resonance imaging. Together with the enhanced luminescence efficiency, upconverting nanoparticles might represent an efficient probe for bimodal in vitro and in vivo imaging of cells in regenerative medicine, drug delivery, and/or photodynamic therapy.

• Publikační typ
• časopisecké články MeSH

Instant Blood-Mediated Inflammatory Reaction (IBMIR) is a major cause of graft loss during pancreatic islet transplantation, leading to a low efficiency of this treatment method and significantly limiting its broader clinical use. Within the procedure, transplanted islets obstruct intrahepatic portal vein branches and consequently restrict blood supply of downstream lying liver tissue, resulting typically in ischemic necrosis. The extent of ischemic lesions is influenced by mechanical obstruction and inflammation, as well as subsequent recanalization and regeneration capacity of recipient liver tissue. Monitoring of immediate liver perfusion impairment, which is directly related to the intensity of post-transplant inflammation and thrombosis (IBMIR), is essential for improving therapeutic and preventive strategies to improve overall islet graft survival. In this study, we present a new experimental model enabling direct quantification of liver perfusion impairment after pancreatic islet transplantation using ligation of hepatic arteries followed by contrast-enhanced magnetic resonance imaging (MRI). The ligation of hepatic arteries prevents the contrast agent from circumventing the portal vein obstruction and enables to discriminate between well-perfused and non-perfused liver tissue. Here we demonstrate that the extent of liver ischemia reliably reflects the number of transplanted islets. This model represents a useful tool for in vivo monitoring of biological effect of IBMIR-alleviating interventions as well as other experiments related to liver ischemia. This technical paper introduces a novel technique and its first application in experimental animals.

• Klíčová slova
• IBMIR, MRI, Pancreatic islet transplantation, instant blood-mediated inflammatory reaction, liver ischemia, magnetic resonance imaging,
• MeSH
• embolie * komplikace   diagnóza   MeSH
• ischemie * diagnostické zobrazování   etiologie   MeSH
• játra * krevní zásobení   diagnostické zobrazování   patologie   MeSH
• krysa rodu Rattus MeSH
• magnetická rezonanční angiografie metody   MeSH
• přežívání štěpu MeSH
• reprodukovatelnost výsledků MeSH
• teoretické modely MeSH
• transplantace Langerhansových ostrůvků škodlivé účinky   MeSH
• vena portae * MeSH
• vylepšení obrazu metody   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem 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.

• Klíčová slova
• F-19 magnetic resonance imaging, Nanoparticles, Optical imaging, Pancreatic islets, Transplantation,
• MeSH
• endocytóza MeSH
• fluor chemie   MeSH
• fluorescence MeSH
• Langerhansovy ostrůvky diagnostické zobrazování   MeSH
• luminiscenční měření * MeSH
• magnetická rezonanční tomografie * MeSH
• modely u zvířat MeSH
• molekulární zobrazování * MeSH
• potkani inbrední LEW MeSH
• potkani transgenní MeSH
• přežití tkáně MeSH
• tkáňové podpůrné struktury chemie   MeSH
• transplantace Langerhansových ostrůvků * MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fluor MeSH

Magnetoliposomes (MLs) were synthesized and tested for longitudinal monitoring of transplanted pancreatic islets using magnetic resonance imaging (MRI) in rat models. The rat insulinoma cell line INS-1E and isolated pancreatic islets from outbred and inbred rats were used to optimize labeling conditions in vitro. Strong MRI contrast was generated by islets exposed to 50 µg Fe/ml for 24 hours without any increased cell death, loss of function or other signs of toxicity. In vivo experiments showed that pancreatic islets (50-1000 units) labeled with MLs were detectable for up to 6 weeks post-transplantation in the kidney subcapsular space. Islets were also monitored for two weeks following transplantation through the portal vein of the liver. Hereby, islets labeled with MLs and transplanted under the left kidney capsule were able to correct hyperglycemia and had stable MRI signals until nephrectomy. Interestingly, in vivo MRI of streptozotocin induced diabetic rats transplanted with allogeneic islets demonstrated loss of MRI contrast between 7-16 days, indicative of loss of islet structure. MLs used in this study were not only beneficial for monitoring the location of transplanted islets in vivo with high sensitivity but also reported on islet integrity and hereby indirectly on islet function and rejection.

• MeSH
• experimentální diabetes mellitus chemicky indukované   metabolismus   patologie   MeSH
• hyperglykemie metabolismus   patologie   MeSH
• inzulin metabolismus   MeSH
• játra metabolismus   patologie   MeSH
• kontrastní látky metabolismus   MeSH
• krysa rodu Rattus MeSH
• kultivované buňky MeSH
• Langerhansovy ostrůvky metabolismus   patologie   MeSH
• longitudinální studie MeSH
• magnetická rezonanční tomografie metody   MeSH
• magnetické nanočástice aplikace a dávkování   MeSH
• potkani inbrední LEW MeSH
• potkani Wistar MeSH
• streptozocin farmakologie   MeSH
• transplantace Langerhansových ostrůvků metody   MeSH
• vena portae metabolismus   patologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• inzulin MeSH
• kontrastní látky MeSH
• magnetické nanočástice MeSH
• streptozocin MeSH

BACKGROUND: In vitro labelling of cells and small cell structures is a necessary step before in vivo monitoring of grafts. We modified and optimised a procedure for pancreatic islet labelling using bimodal positively charged poly(lactic-co-glycolic acid) nanoparticles with encapsulated perfluoro crown ethers and indocyanine green dye via microporation and compared the method with passive endocytosis. RESULTS: Pancreatic islets were microporated using two pulses at various voltages. We tested a standard procedure (poration in the presence of nanoparticles) and a modified protocol (pre-microporation in a buffer only, and subsequent islet incubation with nanoparticles on ice for 10 min). We compared islet labelling by microporation with labelling by endocytosis, i.e. pancreatic islets were incubated for 24 h in a medium with suspended nanoparticles. In order to verify the efficiency of the labelling procedures, we used 19F magnetic resonance imaging, optical fluorescence imaging and confocal microscopy. The experiment confirmed that microporation, albeit fast and effective, is invasive and may cause substantial harm to islets. To achieve sufficient poration and to minimise the reduction of viability, the electric field should be set at 20 kV/m (two pulses, 20 ms each). Poration in the presence of nanoparticles was found to be unsuitable for the nanoparticles used. The water suspension of nanoparticles (which served as a surfactant) was slightly foamy and microbubbles in the suspension were responsible for sparks causing the destruction of islets during poration. However, pre-microporation (poration of islets in a buffer only) followed by 10-min incubation with nanoparticles was safer. CONCLUSIONS: For labelling of pancreatic islets using poly(lactic-co-glycolic acid) nanoparticles, the modified microporation procedure with low voltage was found to be safer than the standard microporation procedure. The modified procedure was fast, however, efficiency was lower compared to endocytosis.

• Klíčová slova
• 19F magnetic resonance imaging, Bimodal nanoparticles, Cell labelling, Confocal microscopy, Endocytosis, Fluorescence imaging, Microporation, Pancreatic islets,
• Publikační typ
• časopisecké články MeSH

PURPOSE: An artificial site for cell or pancreatic islet transplantation can be created using a polymeric scaffold, even though it suffers subcutaneously from improper vascularisation. A sufficient blood supply is crucial for graft survival and function and can be enhanced by transplantation of mesenchymal stem cells (MSCs). The purpose of this study was to assess the effect of syngeneic MSCs on neoangiogenesis and cell engraftment in an artificial site by multimodal imaging. PROCEDURES: MSCs expressing a gene for luciferase were injected into the artificial subcutaneous site 7 days after scaffold implantation. MRI experiments (anatomical and dynamic contrast-enhanced images) were performed on a 4.7-T scanner using gradient echo sequences. Bioluminescent images were acquired on an IVIS Lumina optical imager. Longitudinal examination was performed for 2 months, and one animal was monitored for 16 months. RESULTS: We confirmed the long-term presence (lasting more than 16 months) of viable donor cells inside the scaffolds using bioluminescence imaging with an optical signal peak appearing on day 3 after MSC implantation. When compared to controls, the tissue perfusion and vessel permeability in the scaffolds were significantly improved at the site with MSCs with a maximal peak on day 9 after MSC transplantation. CONCLUSIONS: Our data suggest that the maximal signal obtained by bioluminescence and magnetic resonance imaging from an artificially created site between 3 and 9 days after MSC transplantation can predict the optimal time range for subsequent cellular or tissue transplantation, including pancreatic islets.

• Klíčová slova
• Bioluminescence, DCE, Dynamic contrast-enhanced MRI, Magnetic resonance imaging, Mesenchymal stem cells, Vascularisation,
• MeSH
• kontrastní látky MeSH
• luminiscenční měření MeSH
• magnetická rezonanční tomografie MeSH
• mezenchymální kmenové buňky cytologie   MeSH
• multimodální zobrazování * MeSH
• potkani inbrední LEW MeSH
• regionální krevní průtok fyziologie   MeSH
• reprodukovatelnost výsledků MeSH
• tkáňové podpůrné struktury MeSH
• transplantace mezenchymálních kmenových buněk * MeSH
• umělé buňky * MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kontrastní látky MeSH

Diabetes is a disorder characterized by beta-cell loss or exhaustion and insulin deficiency. At present, knowledge is lacking on the underlying causes and for the therapeutic recovery of the beta-cell mass. A better understanding of diabetes pathogenesis could be obtained through exact monitoring of the fate of beta-cells under disease and therapy conditions. This could pave the way for a new era of intervention by islet replacement and regeneration regimens. Monitoring the beta-cell mass requires a reliable method for noninvasive in vivo imaging. Such a method is not available at present due to the lack of a beta-cell-specific contrast agent. The only existing method to monitor islet cells in vivo consists of labeling islet transplants with iron nanoparticles prior to transplantation and visualization of the transplanted islets by magnetic resonance imaging (MRI). Therefore, accurate assessment of the native beta-cell mass is still limited to autopsy studies. Endeavors to find a biological structure specific for beta-cells led to the discovery of potential candidates that have been tested for noninvasive imaging. Among them are the ligand to the vesicular monoamine transporter type 2 (VMAT-2), which is called dihydrotetrabenazine (DTBZ), antibodies to zinc transporter (ZnT-8) and the monoclonal antibody IC2. While DTBZ and antibodies to ZnT-8 showed binding activities to more than beta-cells, the anti-IC2 monoclonal antibody showed binding properties exclusively to insulin-producing beta-cells. This effect was demonstrated in many previous investigations, and has been further substantiated more recently. Thus, at present, IC2 seems to be the only useful marker for noninvasive functional imaging of native beta-cells. Experiments with a radioisotope-chelated IC2 structure on pancreas ex vivo showed that the tracer specifically bound to the beta-cell surface and could be detected by nuclear imaging. In the near future, these promising findings may offer a new way to monitor the beta-cell mass in vivo under disease and therapy conditions so that we can learn more about diabetes pathogenesis and options for disease prevention.

• Publikační typ
• časopisecké články MeSH