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Pancreatic islets (PIs) transplantation is an alternative approach for the treatment of severe forms of type 1 diabetes (T1D). To monitor the success of transplantation, it is desirable to follow the location of engrafted PIs non-invasively. In vivo magnetic resonance imaging (MRI) of transplanted PIs is a feasible cell tracking method; however, this requires labeling with a suitable contrast agent prior to transplantation. We have tested the feasibility of cationic magnetoliposomes (MLs), compared to commercial contrast agents (Endorem and Resovist), by labeling insulinoma cells and freshly isolated rat PIs. It was possible to incorporate Magnetic Ressonance (MR)-detectable amounts of MLs in a shorter time (4 h) when compared to Endorem and Resovist. MLs did not show negative effects on the PIs' viability and functional parameters in vitro. Labeled islets were transplanted in the renal sub-capsular region of healthy mice. Hypointense contrast in MR images due to the labeled PIs was detected in vivo upon transplantation, while MR detection of PIs labeled with Endorem and Resovist was only possible after the addition of transfection agents. These findings indicate that MLs are suitable to image PIs, without affecting their function, which is promising for future longitudinal pre-clinical and clinical studies involving the assessment of PI transplantation. [ABSTRACT FROM AUTHOR]

Nano-silicon dioxide (SiO2) is used nowadays in several biomedical applications such as drug delivery and cancer therapy, and is produced on an industrial scale as additive to paints and coatings, cosmetics and food. Data regarding the long-term biokinetics of SiO2 engineered nanoparticles (ENPs) is lacking. In this study, the whole-body biodistribution of SiO2 core-shell ENPs containing a paramagnetic core of Fe3O4 was investigated after a single exposure via intravenous injection or intratracheal instillation in mice. The distribution and accumulation in different organs was evaluated for a period of 84 days using several techniques, including magnetic resonance imaging, inductively coupled plasma mass spectrometry, X-ray fluorescence and X-ray absorption near edge structure spectroscopy. We demonstrated that intravenously administered SiO2 ENPs mainly accumulate in the liver, and are retained in this tissue for over 84 days. After intratracheal instillation, an almost complete particle clearance from the lung was seen after 84 days with distribution to spleen and kidney. Furthermore, we have strong evidence that the ENPs retain their original core-shell structure during the whole observation period. This work gives an insight into the whole-body biodistribution of SiO2 ENPs and will provide guidance for further toxicity studies. [ABSTRACT FROM AUTHOR]

Among the wide variety in iron oxide nanoparticles which are routinely used as magnetic resonance imaging (MRI) contrast agents, magnetoliposomes (MLs) take up a special place. In the present work, the two main types (large and small MLs) are defined and their specific features are commented. For both types of MLs, the flexibility of the lipid coating allows for efficient functionalization, enabling bimodal imaging (e.g., MRI and fluorescence) or the use of MLs as theranostics. These features are especially true for large MLs, where several magnetite cores are encapsulated within a single large liposome, which were found to be highly efficient theranostic agents. By carefully fine-tuning the number of magnetite cores and attaching Gd-complexes onto the liposomal surface, the large MLs can be efficiently optimized for dynamic MRI. A special type of MLs, biogenic MLs, can also be efficiently used in this regard, with potential applications in cancer treatment and imaging. Small MLs, where the lipid bilayer is immediately attached onto a solid magnetite core, give a very high r/ r ratio. The flexibility of the lipid bilayer allows the incorporation of poly(ethylene glycol)-lipid conjugates to increase blood circulation times and be used as bone marrow contrast agents. Cationic lipids can also be incorporated, leading to high cell uptake and associated strong contrast generation in MRI of implanted cells. Unique for these small MLs is the high resistance the particles exhibit against intracellular degradation compared with dextran- or citrate-coated particles. Additionally, intracellular clustering of the iron oxide cores enhances negative contrast generation and enables longer tracking of labeled cells in time. WIREs Nanomed Nanobiotechnol 2011 3 197-211 DOI: 10.1002/wnan.122 For further resources related to this article, please visit the [ABSTRACT FROM AUTHOR]