Leveraging tears for diagnosis

2021 10 06 20 31 5504 Nanotechnology 400

A new nanoscale method being developed by an international team of researchers uses tears for fast and accurate disease diagnosis.

The researchers recently reported in ACS Nano that they have developed a nanoporous membrane-based purification method, dubbed Exodus, that provides a fast and accurate way of testing exomes for disease signatures.

The method has proven to be faster and more sensitive than ultracentrifugation (UC) and size exclusion chromatography (SEC), two of the most common methods for isolating tear exosomes.

Small extracellular vesicles (sEVs, or exosomes) in tears have been shown to provide multiple signatures of diseases. However, the persistent problem in leveraging them in diagnostics is that they're extremely small. They are, in fact, on the nanoscale, and this nanoscale has left a range of diagnostic approaches ineffective in testing sEVs.

"Our approach shows a fast processing time (less than 5 minutes) and high recovered yield with a relatively high purity, which allows us to obtain more proteins and miRNAs through the tear-extracellular vesicles per drop than in urine or blood and reach the aim for tear-exosome-based precision medicine (i.e., molecular diagnosis)," said Fei Liu, a professor at Wenzhou Medical University in China and one of the principal investigators in the research.

Liu and his colleagues have used their Exodus technology to further enable an "Incorporated Tear Exosomes Analysis via Rapid-isolation System" (iTEARS). Exodus itself consists of a sample reservoir coupling with a dual nanoporous membrane and two outlets connected to a negative pressure oscillation system.

To achieve fast exosome isolation and purification, periodic negative pressure switching is applied on two sides of the device, which can drive the sample, entrap the larger-sized exosomes, free the small fragments (e.g., proteins, nucleic acids), and reduce the aggregations of biomolecules and exosomes on membranes.

"With this system, we can obtain enhanced yield and purity, reduce processing time, and extend the range of processing volume," said Liu. "The purified exosomes benefit downstream analysis, including proteomics, sequencing, PCR, or ELISA."

Liu said that he and his colleagues plan to expand the understanding of clear biological communications via exosomes in the development of pathogenesis. Liu expects that this will have an impact on the precision molecular diagnosis of different diseases.

In even more ambitious goals, Liu hopes that this tool will help in discovering the molecular fingerprints of emotional health conditions, as well as the molecular expression and consequences of psychological stress manifested through human tears.

"We hope to provide a clinical translation method for tear-based molecular diagnostics and prognostics not only for eye-related diseases, but also for cancers, diabetes mellitus, neurologic diseases, and the biological functions of emotional tears," said Liu.

One of the limitations in developing methods for testing exomes has been the general lack of realization in the clinical community that tears contain rich clinical information about different parts of our body, according to Liu. This lack of understanding exists even though human lacrimal glands secrete tears in the eyelids through filtration from blood plasma, which circulates through the entire body, collecting exosomes from organs and tissues.

"Tears are also relatively pure, with low potential contaminant interference directly correlated with circulating fluids such as blood," added Liu.

Because of the qualities of tears in our bodies, Liu believes that collection will grow in attention, and ultimately use, as a fast and noninvasive diagnostic method in point-of-care studies. The most critical step in moving this technology forward, according to Liu, is obtaining more large-scale clinical tests to demonstrate the potential of tear-based molecular diagnosis.

Liu added: "In this work, we aim to establish a novel platform that can facilitate tear-exosome-based studies in both disease diagnosis and pathogenesis. We have shown the diagnosis potential of exosomal levels and their cargos in ocular diseases, and we hope to show more detailed applications with large-scale cohorts in future works."

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