June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Imaging Novel Ruthenium bipyridine-based Nanophotoswitches in Retina
Author Affiliations & Notes
  • Lan Yue
    Ophthalmology, USC Eye Institute, University of Southern California, Los Angeles, CA
  • Steven Walston
    Biomedical Engineering, University of Southern California, Los Angeles, CA
  • Mingyi Sonia Lin
    Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA
  • Melanie Pribisko
    Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
  • Dennis Doughurty
    Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
  • Robert Grubbs
    Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
  • Harry Gray
    Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
  • Robert Chow
    Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA
  • Mark S Humayun
    Ophthalmology, USC Eye Institute, University of Southern California, Los Angeles, CA
  • Footnotes
    Commercial Relationships Lan Yue, None; Steven Walston, None; Mingyi Lin, None; Melanie Pribisko, None; Dennis Doughurty, None; Robert Grubbs, None; Harry Gray, None; Robert Chow, None; Mark Humayun, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 1676. doi:
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      Lan Yue, Steven Walston, Mingyi Sonia Lin, Melanie Pribisko, Dennis Doughurty, Robert Grubbs, Harry Gray, Robert Chow, Mark S Humayun; Imaging Novel Ruthenium bipyridine-based Nanophotoswitches in Retina. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1676.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Nanophotoswitches (NPSs) offer a new tool for optical stimulation of neuronal activity, in vitro and also potentially in vivo. Our group previously reported a ruthenium bipyridine (Rubpy)-based NPS that inserts into the plasma membrane and upon visible illumination generates an electrical dipole, triggering action potentials in adrenal chromaffin cells. We have recently demonstrated that after intravitreal injection of this NPS into the eyes of blind rats, illumination of the eye elicited electrical activity in the contralateral superior colliculus. To better understand the site of action of the NPS in retina, we examined the distribution of the molecules in different retinal layers after intravitreal injection.

Methods: Rubpy molecules can be visualized by their luminescence (610 nm) upon visible wavelength illumination (460 nm). To resolve the luminescence from different retinal layers, a rapid-scan two-photon imaging system (LaVison) was used (Ti:Sapphire laser tuned to 900 nm). Intravitreal injection (1 mM, 4 μL Rubpy-based NPSs in BSS), followed by eye removal and retina isolation 2-5 hrs after, was performed on young RCS rats. Luminescence images of the wholemount retina were captured by an EM-CCD camera (Andor).

Results: At 2 hrs after intravitreal injection and with continuous superfusion of Ames medium, luminescence was confined near the injection site. Luminescence was observed localized to surface membranes of axons and somata of retinal ganglion cells (RGC), demonstrating the impermeability of the cell membrane to the NPS molecules. The outer retina did not show significant luminescence. After 3 additional hours, luminescence was more diffused within the RGC layer and still did not extend to the outer retina.

Conclusions: This study shows marked staining of RGC layer by intravitreally injected Rubpy-based NPS molecules, consistent with the hypothesis that the photoactivated NPS molecules induce electrical activity in the superior colliculus by acting on the RGCs that deliver electrical signals to the visual pathway outside the eyes. Distinct from other nano-scale optical cellular modulating approaches using optogenetics or azobenzene-based photoswitches, the NPS approach obviates the need for gene manipulation or toxic UV illumination, highlighting its potential in generating high-acuity prosthetic vision in patients blinded by retinal degenerative diseases.

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