Magnetic Nanoparticle Technology for Ocular Therapeutics

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Magnetic Nanoparticle Technology for Ocular
Therapeutics
ASCRS 2009 Anita R. Shirodkar, MD Ying Hu,
PhD Hemalatha Raju, BSc Anil Vedula, MD Alejandra
Weissman, BA Jeffrey L. Goldberg, MD, PhD
No financial interests to disclose
Financial Support NIH R21-EY017971 (JLG), NEI
P30 Core Grant EY014801, Unrestricted grant from
Research to Prevent Blindness at the University
of Miami
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Magnetic Particles and Optic Nerve Injury

• Magnetic nanoparticles may be used for ocular
  therapeutics
• Drug delivery, cell replacement therapy, gene
  therapy
• Ocular toxicity from these particles remains
  unknown
• Retinal ganglion cell (RGC) axon damage is
  important in the pathogenesis of many
  degenerative diseases
• Glaucoma, optic neuritis, optic ischemia, other
  optic neuropathies
• In all cases, RGCs are unable to regenerate their
  axons after optic nerve injury
• Could magnetic particles play a role in axon
  stimulation?

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Mechanical Tension Can Elongate Axons In Vitro

• Applying mechanical tension to a neuron can
  stimulate axon elongation in vitro.
• Prior research by Bray, et al, showed that by
  applying a direct towing force to neurons via
  glass microneedles can elicit axon elongation.

Neuron
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Magnetically Applied Mechanical Tension In Vitro
Magnetic nanoparticle
Nerve cell
DeSilva et al
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Can Magnetic Nanoparticles Localize to Injured
RGC Axons?

• In order to apply magnetic field-induced
  mechanical tension in vivo, we must first attempt
  to localize magnetic nanoparticles to an optic
  nerve injury site.

Magnetic nanoparticles
Optic nerve injury
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Methods of Nanoparticle Injection and Localization
Rat sacrificed after 24 hours
Sections viewed with fluorescence microscope
Optic nerve dissected in live anesthetized rat
Flourescence-labeled 50 nm magnetic
nanoparticles injected into nerve
Optic nerve removed sectioned
Forceps crush injury to optic nerve
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Injected Nanoparticles Can Localize to Distal
Axon Tip
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Injected Magnetic Nanoparticles Can Be Found
Within Cells
Confocal microscopy
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Injected Magnetic Nanoparticles Label Cells In
Vivo
Nanoparticles on cell surface
Nanoparticles in vesicles
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Magnetic Nanoparticles Are Nontoxic to Ocular
Structures

• Magnetic nanoparticle toxicity was evaluated in
  rats.
• Anterior chamber and intravitreal injections
• PBS versus 50 nm and 4 µm particles
• Parameters were evaluated at 1 hour and 7 days
• Retinal layer cell densities, IOP readings,
  endothelial cell counts, histology,
  immunofluorescence
• Magnetic nanoparticles had no demonstrated
  toxicity by any of the methods tested.
• Microparticles were found to have statistically
  lower endothelial cell counts at 7 days

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Magnetic Nanoparticles A Promising
Future

• Magnetic nanoparticles injected into a rat optic
  nerve can localize to the injured, distal axon
  tips.
• A subset of these particles are endocytosed
  locally by optic nerve cells.
• Ongoing experiments are directed at identifying
  and optimizing the subcellular localization of
  the nanoparticles, particularly focusing on
  enhancing axon binding specificity.
• Magnetic nanoparticles do not appear to be toxic
  to ocular structures.

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Future Directions
Explants
Magnet
Magnetic nanoparticles
Axon elongation
Injury Site
Magnet
In vivo elongation
Axon elongation
Magnetic nanoparticles