In vivo imaging of islet transplantation using PLGA nanoparticles containing iron oxide and indocyanine green.

PURPOSE: We determined whether poly(lactic-co-glycolic acid) nanoparticles would be a useful reagent for the successful monitoring of isolated islets by magnetic resonance imaging and optical imaging systems, without clinically relevant toxicity in vitro or in vivo. METHODS: We used iron oxide for MR imaging and a cyanide dye approved by the Food and Drug Administration (indocyanine green) for optical imaging and estimated the in vivo detection of transplanted pancreatic islets. RESULTS: The poly(lactic-co-glycolic acid) nanoparticles were associated with the islets in vitro and were successfully detected by 4.7 T (MR) and optical imaging, without other toxic effects. When labeled islets were transplanted under the mouse kidney capsule, in vivo T2/ T2*-weighted scans with 4.7 T MR detected as few as 300 labeled islets by 4 weeks. Optical in vivo imaging revealed indocyanine green fluorescence by 2 and 4 days after transplantation of islets containing 250 and 500 µg/mL poly(lactic-co-glycolic acid) nanoparticles, respectively. These results were further supported by the immunohistochemical results for insulin and iron in the recipient mouse kidney and pancreas. CONCLUSIONS: Taken together, these data indicate that poly(lactic-co-glycolic acid) nanoparticles may be used to label transplanted islets and may be imaged with in vivo MR and optical imaging systems.