Related Experiment Video
Updated: Jun 1, 2026
Experimental Glaucoma Induced by Ocular Injection of Magnetic Microspheres
Published on: February 2, 2015
Evaluation of magnetic micro- and nanoparticle toxicity to ocular tissues
Hemalatha B Raju1, Ying Hu, Anil Vedula
1Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States of America.
Purpose:
Magnetic nanoparticles (MNPs) may be used for focal delivery of plasmids, drugs, cells, and other applications. Here we ask whether such particles are toxic to ocular structures.
Methods:
To evaluate the ocular toxicity of MNPs, we asked if either 50 nm or 4 µm magnetic particles affect intraocular pressure, corneal endothelial cell count, retinal morphology including both cell counts and glial activation, or photoreceptor function at different time points after injection. Sprague-Dawley rats (n = 44) were injected in the left eye with either 50 nm (3 µl, 1.65 mg) or 4 µm (3 µl, 1.69 mg) magnetic particles, and an equal volume of PBS into the right eye. Electroretinograms (ERG) were used to determine if MNPs induce functional changes to the photoreceptor layers. Enucleated eyes were sectioned for histology and immunofluorescence.
Results:
Compared to control-injected eyes, MNPs did not alter IOP measurements. ERG amplitudes for a-waves were in the 100-250 µV range and b-waves were in the 500-600 µV range, with no significant differences between injected and non-injected eyes. Histological sectioning and immunofluorescence staining showed little difference in MNP-injected animals compared to control eyes. In contrast, at 1 week, corneal endothelial cell numbers were significantly lower in the 4 µm magnetic particle-injected eyes compared to either 50 nm MNP- or PBS-injected eyes. Furthermore, iron deposition was detected after 4 µm magnetic particle but not 50 nm MNP injection.
Conclusions:
Intravitreal or anterior chamber injections of MNPs showed little to no signs of toxicity on retinal structure, photoreceptor function or aqueous drainage in the eye. Our results suggest that MNPs are safe for intraocular use.
Insights
Magnetic nanoparticles (MNPs) show minimal ocular toxicity in rats, with no impact on retinal structure or function. Larger 4 µm MNPs caused a temporary decrease in corneal endothelial cells, suggesting potential localized effects.
Area of Science:
- Ophthalmology
- Biomaterials Science
- Nanotechnology
Background:
- Magnetic nanoparticles (MNPs) offer potential for targeted delivery in various biomedical applications.
- Assessing the safety of MNPs for ocular use is crucial for their clinical translation.
Purpose of the Study:
- To evaluate the ocular toxicity of 50 nm and 4 µm magnetic nanoparticles (MNPs).
- To determine the effects of MNPs on intraocular pressure, corneal endothelium, retinal morphology, and photoreceptor function.
Main Methods:
- Sprague-Dawley rats received intravitreal injections of 50 nm or 4 µm MNPs.
- Ocular parameters including intraocular pressure, corneal endothelial cell count, retinal histology, and electroretinograms (ERGs) were assessed.
- Immunofluorescence was used to detect glial activation and iron deposition.
Main Results:
- MNPs did not significantly alter intraocular pressure or ERG measurements.
- Histology revealed minimal differences between MNP-injected and control eyes.
- A significant decrease in corneal endothelial cells was observed at 1 week post-injection with 4 µm MNPs, with detected iron deposition.
Conclusions:
- Intravitreal injection of MNPs demonstrated low ocular toxicity.
- MNPs appear safe for intraocular use, with potential localized effects noted for larger particle sizes.
