A research team led by Prof. CHEN Yan from the Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences, and their collaborators developed a novel digital droplet microfluidic flow cytometry technique, called Nano-DMFC, for in-situ analysis of multiple miRNAs in single circulating tumor cells (CTCs).

The study was published in Small on July 14.

In liquid biopsy studies, CTCs detection strategies based on surface epithelial markers are widely used. However, they suffer from low specificity in distinguishing between CTCs and epithelial cells in hematopoietic cell population.

Tumor-associated miRNAs within CTCs are emerging as new biomarkers due to their high correlation with tumor development and progress. But it is still challenging to perform in-situ analysis of multiple miRNAs of single living CTCs currently. 

In this study, the novel two-dimensional nanomaterial, metal organic framework (MOF), provided new ideas for live cell probes due to its controllable structure and diverse functions.

In Nano-DMFC, the researchers integrated a novel 2D MOF nanosensor into a droplet microfluidic flow cytometer, achieving in situ, multiplex, and quantitative analysis of miRNAs in single living CTCs with high throughput. They established the 2D MOF-based fluorescent resonance energy transfer nanosensors by conjugating dual-color fluorescence dye-labeled DNA probes on MOF nanosheet surface.

The Nano-DMFC consists of three components: a single-cell droplet generator, a nanoprobe microinjection unit, and a droplet fluorescence detection unit. 2D MOF-based nanoprobes were precisely microinjected into each single-cell encapsulated droplets to achieve dual miRNA characterization in single cancer cell.

This Nano-DMFC platform detected dual miRNAs at single-cell resolution in 10 mixed positive MCF-7 (a breast cancer cell line) cells out of 10,000 negative epithelial cells in serum biomimic samples.

"Our proposed Nano-DMFC platform shows good reproductivity in the recovery experiment of spiked blood samples, which demonstrated the high potential for early diagnosis and prognosis of CTC-based cancer," said Prof. CHEN Yan.