Labeling and tracking of human pancreatic islets using carbon nanotubes

Limited tools are available for the non-invasive monitoring of transplanted islets. In this study, we have compared the widely used superparamagnetic iron oxide nanoparticle ferumoxide (Endorem®) and multiwalled carbon nanotubes (MWCNTs) for islet cell labeling and tracking. INS-1E cells and human pancreatic islets isolated from 12 non-diabetic cadaveric organ donors (age: 62±16 yr, BMI: 24.6±3.3 kg/m2) were incubated with 50 μg/ml Endorem® or 15 μg/ml MWCNTs and studied after 7 or 14 days to assess beta cell morphology, ultrastructure, function, cell survival and in-vitro and in-vivo magnetic resonance imaging (MRI). Light and electron (EM) microscopy showed the well-maintained morphology and ultrastructure of both INS-1E and human islets during the incubation. EM also revealed the presence of Endorem® and MWCNTs within the beta but not the alpha cells. The compounds did not affect beta cell function and viability, and in-vitro MRI showed that labeled INS-1E cells and human islets could be imaged. Finally, MWCNT labeled human islets were successfully transplanted into the subcutis of rats localized in the desired site via magnetic field and tracked by MRI. These data suggest that MWCNTs can be an alternative labeling compound to be used with human islets for experimental and transplantation studies.