Magnetic retraction: A viable method for the purification of encapsulated islet grafts

Islet cell transplantation is a promising option for the restoration of normal glucose homeostatsis in patients with type-1 diabetes. But problems remain regarding the efficient use of donor cells and the prevention of graft rejection by the host immune system. Previously, we were able to show that xenotransplantation of microencapsulated rat and human islets cells can achieve life-long graft function in immunocompetent diabetic mice without the need for immunosuppression [1]. Since the microencapsulation of islets results in a significant amount of empty capsules, and since graft volume is a crucial issue, we developed a new method which uses magnetic labeling and separation of the microencapsulated islets witch supramagnetic iron particles (SPIO) in order to eliminate empty capsules. For this purpose, rat islets were isolated and labeled with two different concentrations of SPIO (3 and 30µl/ml Resovist®, respectively) before microencapsulation in alginate beads as described [1]. Before transplantation into diabetic mice, the magnetic capsules were separated from the empty capsules using a newly developed linear magnetic flow apparatus. Using this method we were able to reduce the ratio of empty capsules (EC) to islet containing capsules (IC) from 4:1 to at least 2:1 or 1:1 in the low (3µg/ml) and high (30µg/ml) SPIO concentration group, respectively. In vitro viability and functionality assessment using the insulin stimulation index did not show any differences between SPIO-labeted islets and freshly isolated unlabeled islets. For proof of in vivo function 3500 islet equivalents (Ieq) of SPIO-labeled islets from both concentrations were transplanted in the peritoneal cavity of streptozotozin-diabetic immunocompetent balb/c mice, resulting in long term (>30 weeks) normoglycemia. We conclude, that magnetic separation of SPIO-labelled encapsulated islets is a clinically safe and effective principle to significantly decrease the graft volume without impairing graft quality and function

Labeling Human Melanoma Cells With SPIO

Objectives: To use the superparamagnetic iron oxide (SPIO) contrast agent Resovist (±transfection agent) to label human melanoma cells and determine its effects on cellular viability, microstructure, iron quantity, and magnetic resonance imaging (MRI) detectability. Materials and Methods: Human SK-Mel28 melanoma cells were incubated with Resovist (±liposomal transfection agent DOSPER). The cellular iron content was measured, and labeled cells were examined at 1.5 T and 3.0 T. The intracellular and extracellular distributions of the contrast agent were assessed by light and electron microscopy. Results: The incubation of melanoma cells with SPIO does not interfere with cell viability or proliferation. The iron is located both intracellularly and extracellularly as iron clusters associated with the exterior of the cell membrane. Despite thorough washing, the extracellular SPIO remained associated with the cell membrane. The liposomal transfection agent does not change the maximum achievable cellular iron content but promotes a faster iron uptake. The MRI detectability persists for at least 7 days. Conclusion: The transfection agent DOSPER facilitates the efficient labeling of human metastatic melanoma cells with Resovist. Our findings raise the possibility that other Resovist-labeled cells may collect associated extracellular nanoparticles. The SPIO may be available to other iron-handling cells and not completely compartmentalized during the labeling procedure

Torque expression of 0.018 and 0.022 inch conventional brackets

SUMMARY The aim of this study was to assess the effect of the moments generated with low- and high-torque brackets. Four different bracket prescription-slot combinations of the same bracket type (Mini Diamond® Twin) were evaluated: high-torque 0.018 and 0.022 inch and low-torque 0.018 and 0.022 inch. These brackets were bonded on identical maxillary acrylic resin models with levelled and aligned teeth and each model was mounted on the orthodontic measurement and simulation system (OMSS). Ten specimens of 0.017×0.025 inch and ten 0.019×0.025 inch stainless steel archwires (ORMCO) were evaluated in the low- and high-torque 0.018 inch and 0.022 inch brackets, respectively. The wires were ligated with elastomerics into the brackets and each measurement was repeated once after religation. Two-way analysis of variance and t-test were conducted to compare the generated moments between wires at low- and high-torque brackets separately.The maximum moment generated by the 0.017×0.025 inch stainless steel archwire in the 0.018 inch brackets at +15 degrees ranged from 14.33 and 12.95 Nmm for the high- and low-torque brackets, respectively. The measured torque in the 0.022 inch brackets with the 0.019×0.025 inch stainless steel archwire was 9.32 and 6.48 Nmm, respectively. The recorded differences of maximum moments between the high- and low-torque series were statistically significant. High-torque brackets produced higher moments compared with low-torque brackets. Additionally, in both high- and low-torque configurations, the thicker 0.019×0.025 inch steel archwire in the 0.022 inch slot system generated lower moments in comparison with the 0.017×0.025 inch steel archwire in the 0.018 inch slot system