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Richard M. Awdeh, Adam de la Zerda, Victor L. Perez, Marco Rugerri, Sanjiv Gambhir; Optical Coherence Molecular Imaging Using Gold Nanorods In Living Mice Eyes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):455.
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Optical Coherence Tomography (OCT) is a powerful imaging modality to visualize various structures in the eye at very high spatial resolution. The contrast in an OCT image is mainly due to the tissue optical scattering properties. Hence, an OCT image primarily visualizes structures. For physiological and molecular features to be visualized by OCT, an exogenous contrast agent must be used. Such contrast agent should produce a strong OCT signal, beyond the background tissue OCT signal. Gold nanorods (GNRs) possess a tunable and strong optical absorbance due to their plasmon resonance. In this work we evaluate GNRs as OCT contrast agents and show they have unprecedented sensitivity in living mice corneas.
The imaging agent we used is a gold nanorod (GNR) 15 nm in diameter and 45 nm in length. These dimensions resulted in a peak absorbance at 780 nm, which matches well with the laser source in the OCT imaging system that we used. The gold nanorods were coated with polyethylene-glycol-5000 (PEG5000) to render water- solubility to the gold nanorods. Next we injected a series of concentrations of these particles into the corneal stroma of mice and performed in vivo imaging using OCT.
A 0.5 nM concentration of gold nanorods created a strong contrast in the cornea OCT images, with a signal 33% higher than control mice (p<0.05 for all). We measured the minimal detectable concentration of the gold nanorods by injecting decreasing concentration of particles into the mice corneas. The in vivo sensitivity of our particles was found to be 370 pM. The OCT signal recorded from the mice corneas was linear to the gold nanorods concentration (R2 = 0.981)
We have shown the feasibility of gold nanorods to be used as OCT contrast agents. To our knowledge, this is the first demonstration of gold nanorods as OCT contrast agents in living animals. We expect gold nanorods to be proven as useful OCT contrast agents in various eye diseases.
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