Program Information
Initial Investigations of Up-Converting Nanoparticles (UCNP) for 3D Tissue Imaging in Optical-ECT
S Yoon1*, B Langloss2 , M Boss3 , S Birer4 , M Dewhirst1 , M Oldham1 , (1) Duke University Medical Center, Durham, NC, (2) Duke University, Durham, NC, (3) North Carolina State University, Durham, North Carolina, (4) Duke University School of Medicine, Durham, North Carolina
Presentations
SU-G-IeP4-8 (Sunday, July 31, 2016) 5:30 PM - 6:00 PM Room: ePoster Theater
Purpose: Near-IR absorptive up-converting nanoparticles (UCNPs) is a novel contrast for optical-ECT that allows auto-fluorescence-free 3D imaging of labeled cells in a matrix of large (~1cm³) unsectioned normal tissue. This has the potential to image small metastases or dormant cells that is difficult with down-converting fluorescing dyes due to auto-fluorescence. The feasibility of imaging UCNP in agarose phantoms and a mouse lung is demonstrated, aided by a 3D-printed optical-ECT stage designed to excite UCNP in a mouse lung.
Methods: The UCNP, NaYF₄:Yb/Er (20/2%), studied in this work up-converts 980nm light to visible light peaking sharply at ~540nm. To characterize the UCNP emission as a function of UCNP concentration, cylindrical 2.5%wt agarose phantoms infused with UCNP at concentrations of 25μg/mL and 50μg/mL were exposed to 1.5W 980nm laser coupled to an optical fiber. The fiber was held stably at 1cm above the stage via a custom 3D-printed stage. An optically cleared lung harvested from a BALBc mice was then injected with 100μL of 1mg/mL UCNP solution ex vivo. Tomographic imaging of the UCNP emission in lung was performed.
Results: The laser beam tract is visualized within the agarose phantom. A line profile of UCNP emission at 25μg/mL versus 50μg/mL shows that increasing the UCNP concentration increases emission count. UCNPs injected into a cleared mouse lung disperse throughout the respiratory tract, allowing for visualization and 3D reconstruction. Excitation before and after UCNP injection shows the tissue exhibits no auto-fluorescence at 980nm, allowing clear view of the UCNP without any obscuring features such as conventional down-converting fluorescent tags.
Conclusion: We confirm that up-conversion in tissue circumvents completely tissue auto-fluorescence, which allowed background-free 3D reconstruction of the UCNP distribution. We also confirm that raising the UCNP concentration increases emission and that UCNPs are retained in agarose samples during the optical clearing process.
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