MR Visualization Of Colo Rectal Uptake Of Solid Lipid Nanoparticles In DMH-treated Mice

PurposeTo investigate, by using magnetic resonance (MR) and laser-scanning confocal fluorescence microscope (LSCFM) imaging, colorectal uptake of solid lipid nanoparticles (SLNs) in mice receiving different doses of1,2-dimethylhydrazine (DMH).Materials and MethodsEight mice were sacrificed in a pilot study to establish the experimental protocol and to visualize colorectal uptake of SLNs in normal mice. Gd-DTPA and fluorescein isothiocyanate (FITC)-loaded SLN (Gd-FITC-SLN) enemas were performed on mice receiving DMH for10weeks (group1, n=9) or16weeks (group2, n=7). FITC-SLN enema was performed on4DMH-treated mice (group3). Pre-and post-enema MR examinations were performed to visualize the air-inflated distal colorectum. Histological and LSCFM examinations were performed to verify colorectal malignancy and to track the distribution of SLNs.ResultsHomogeneous enhancements and dense fluorescence (FITC) deposition in colorectal wall were observed in normal mice and1DMH-treated mouse (group1) on fluid attenuated inversion recovery (FLAIR) and LSCFM images, respectively. Heterogeneous mural enhancements were found in6mice (4in group1;2in group2). No visible mural enhancement was observed in the other mice. LSCFM imaging revealed linear fluorescence deposition along the colorectal mucosa (groups1,2,3). Nine intraluminal masses and2prolapsed mass were detected by MR imaging with different enhancement modes and pathologies. Interstitial FITC deposition was identified where obvious enhancement was observed in FLAIR images. Bladder imaging agent accumulations were observed in11of16DMH-treated mice (groups1,2).ConclusionSignificant differences in colorectal uptake and distribution of SLNs was revealed in normal and DMH-treated mice, which may provide a new mechanism of contrast for MR colonography.