Researchers Detect Hidden Leukemia Cells with a Standard Fluorescence Microscope [Unboxing Lab]

[Financial News] A research team led by Professor Choi Seong-yong in the Department of Biomedical Engineering at Hanyang University has developed a technique that can precisely analyze 17 types of protein and gene signals in leukemia cells at once using a standard fluorescence microscope by flattening the cells. The method opens a way to clearly detect subtle cancer signals inside a single cell without expensive specialized equipment.

The new achievement could be used to detect mutated cancer cells that evade existing tests at an early stage. When a leukemia patient is undergoing treatment, proteins on the surface of cancer cells may disappear, making it easy for conventional antibody tests to miss them. Because this technique checks not only surface proteins but also genetic information inside the cell at the same time, it can accurately identify cancer cells that have lost their surface proteins.
The team expects the method to be widely used not only for leukemia but also for precision diagnosis of various cancers with cell-to-cell differences, such as circulating tumor cells in the bloodstream, and for tracking recurrence. Another strength is that it can use the basic fluorescence microscopes already available in most hospitals, rather than ultra-expensive specialized instruments, which could significantly lower testing costs and barriers to access.

Instead of modifying the microscope itself, the team began with a fresh idea: changing the shape of the cells being observed. A standard fluorescence microscope can distinguish signals well on a flat horizontal plane, but it has a limitation in the vertical direction. When signals overlap, they blur into a single large spot. Another problem was photobleaching, in which fluorescent materials lose their signal as if they were burning out when images are taken repeatedly while adjusting the focus up and down to view the entire cell.
Using a simple device made with a 3D printer, the researchers gently pressed the cells flat like hotteok. As the cells became thinner and spread outward, the overlapping fluorescence signals in the vertical direction unfolded across the plane and became easy to distinguish at a glance.
They then attached unique fluorescent barcodes to protein and gene information, and combined that with another indicator: the different rates at which each fluorescent material dims when exposed to light. Even fluorescent materials with similar colors could be clearly distinguished by differences in how quickly their brightness faded.

The study found that the number of microscope images needed dropped from 25 before compression to just 5 after the cells were flattened. As light exposure decreased, the clarity of the fluorescence signals improved by more than 3.6 times, and the accuracy of signal reading rose sharply from 58.8% to 99.7%.
By combining nine fluorescent materials, the team successfully classified a total of 40 independent fluorescent barcodes with complete accuracy. In pre-validation tests using cells, the false-positive rate, where no signal was present but one was incorrectly detected, was 1.3%, while the false-negative rate, where real signals were missed, was 2.8%.
The team then applied the technology to blood cells from 13 leukemia patients and three healthy individuals. As a result, it simultaneously measured 17 targets in a single cell, including 12 cell-surface proteins and 5 RNA transcripts, which are traces left by active genes.
The results of cancer-cell classification showed a very high level of agreement with flow cytometry, the standard diagnostic method used in hospitals. However, RNA detection levels were about one-tenth of those seen in molecular precision testing with Reverse-transcription quantitative PCR (RT-qPCR), suggesting that improving detection sensitivity will be a key follow-up task.
The findings were published online in ACS Sensors, an international journal in the sensor field. They were also selected as an ACS Editors' Choice article and a cover paper by ACS, underscoring their academic value.

[email protected] Kim Man-ki Reporter