New method effectively stains apoptotic retinal cells without requiring intraocular injections

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Azure Biosystems is excited to announce the first published study that uses the Sapphire Biomolecular Imager, and we look forward to the role that Sapphire will play in future studies.

What’s the problem, scientifically speaking?

Labeling neurons is critical for the diagnosis, prognosis, and treatment of retinal degenerative diseases. A common approach is to use a fluorescent probe to tag anionic phosphatidylserine (PS), which cells produce early in apoptosis in order to trigger phagocytosis. Until now, the only way to tag PS was by injecting the label directly into the eye. Not only is this a painful and invasive procedure, but the injection itself can promote retinal degeneration, making this method for labeling PS undesirable for monitoring disease progression.

What have been the technical barriers?

Until now, non-invasive PS probes have not been effective because they do not permeate the vitreous layer of the eye. Barriers in the eye make treatment of ocular disease difficult1, and previous work has focused on delivering PS probes effectively2.

What’s the solution?

Non-invasive in vivo fluorescence imaging of apoptotic retinal photoreceptors

Mazzoni, Francesca, Muller, Claudia, DeAssis, Jonathan, Lew, Deborah, Leevy, W. Matthew, Finnerman, Silvia C.

Scientific Reports 2019 Feb 7; 9(1):1590. PMID: 30733587

The authors found that Texas-red-conjugated PSVue-550, a commercially available probe, effectively binds to apoptotic photoreceptors when administered with an eye dropper. Using this method, they were able to track disease progression in vivo using whole animal imaging and a retinal imaging system in both rat and mouse models of retinal degeneration.

The Sapphire Biomolecular Imager was used to confirm PSVue-550 penetration into the eye. Monitoring of disease progression is now possible in vivo using an eye dropper, replacing the need for injections.

Are there other applications?

The work by Mazzoni, et al. is a significant first step toward using this method in the study and treatment of human retinal disease. We’re proud that the Sapphire’s superior resolution, range, and sensitivity are being used for such important advances.

Where can I learn more?

Learn more about the Sapphire Biomolecular Imager and how it can enhance your research.


1Pearce, W., Hsu, J., & Yeh, S. (2015). Advances in drug delivery to the posterior segment. Current opinion in ophthalmology, 26(3), 233–239.

2Qiu, et al. Single-Cell Resolution Imaging of Retinal Ganglion Apoptosis In Vivo Using a Cell-Penetrating Caspase Activatable Peptide Probe. PLOS ONE 9(2), e88855.

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