Scientists invented optical tweezers-assisted static cell imaging sorting technology

OPSI technical service single-cell multi-omics research group photo

Single-cell multiomics has become a powerful tool in the life sciences, but a precise, low-damage, broad-spectrum, and simple single-cell acquisition method for target phenotypes is a prerequisite for targeted single-cell genome, transcriptome, proteome, or metabolome analysis.

Recently, the Single Cell Center of Qingdao Institute of Bioenergy and Process Research, Chinese Academy of Sciences invented optical tweezers-assisted static cell imaging sorting technology (OPSI), which can “WYSI”, maintain cell in situ activity, and high-throughput sorting of target single cells under brightfield, fluorescence, and Raman imaging, supporting high-quality single-cell genome/transcriptome sequencing. This technology is suitable for a wide spectrum of cells of all sizes, such as bacteria, archaea, fungi, animals and plants, and the human body. The relevant work was published in the international journal “Laboratory on a Chip” in the field of microfluidics.

The reporter learned that brightfield images, fluorescence images, and Raman spectra can reflect the rich phenotypic information of cells, and the single-cell sorting technology that gathers the above information and has the characteristics of single-cell precision index and WYSIWYG has wide applicability in single-cell analysis.

Based on the previous single-cell Raman spectroscopy technology, the single-cell center developed RAGE-Seq, a Raman sorting-sequencing technology for measuring and sorting single cells of target microorganisms in the liquid phase environment. This technology can obtain the chemical fingerprint of the whole single cell through Raman spectroscopy without labeling, so as to quickly identify the physiological characteristics and metabolite changes of living single cells, and more importantly, with the characteristics of its small volume separation reaction, almost complete whole genome information can be obtained from a single cell, which is of great significance for the functional identification and resource development of microorganisms.

However, the operation process of this technology is slightly cumbersome, and the sorting throughput is low, which is difficult for large-scale single-cell sorting and analysis.

In order to solve the above problems, the research team led by Dr. Xu Teng and Li Yuandong of the Single Cell Center, based on Qingdao Xingsai Biotech’s single-cell microdroplet sorting system EasySort Compact, developed a new generation of OPSI-based single-cell sorting coupled culture/sequencing strategy based on RAGE-Seq technology.

According to reports, different from the principle of imaging screening after cells flow through narrow channels one by one in flow cytometry technology, OPSI proposes an idea of static cell imaging sorting, that is, a stable static flow field with a flow rate of 0 is constructed in a microfluidic chip, the sample cells are bound, and planar brightfield, fluorescence imaging or Raman scanning is performed in the flow field to select target cells. The target single cells were then removed from the static flow field by low-cell damage 1064 nm phototweezers and sorted by single-cell droplet wrapping.

The system enables cells to be classified in a precisely indexed manner, “what you see is what you get”, and is widely applicable to single cells of different sizes (1 ~40 μm in diameter) from bacteria, archaea to human cells.

The verification test shows that the single-cell sorting accuracy of OPSI is greater than 99.7%, which ensures the sorting flux of 10~20 cells/min and maintains cell viability at a high level. In addition, OPSI inherits the characteristics of RAGE’s small-size isolation reaction, which significantly reduces the disproportionation phenomenon in traditional single-cell gene amplification. For example, using this system to sort human MCF-7 single cells for RNA-seq results in high-quality and reproducible single-cell transcriptome profiles. The versatility, convenience, flexibility and low cost of OPSI provide a broad application prospect in single-cell multiomics research.

Based on the above characteristics of OPSI, the Single Cell Center and Qingdao Xingsai Biotechnology have cooperated to launch a series of automated and intelligent single-cell microdroplet sorting systems, and cooperated with leading manufacturers of international microscopes and microscopic spectrometers (such as Thermo Fisher Scientific, Horiba HORIBA, etc.) to promote them in the global scientific instrument market.

The work was chaired by Ma Bo and Xu Jian, researchers of the single cell center of the institute, completed in cooperation with Qingdao Xingsai Biotechnology, and was funded by the National Key Research and Development Program, the Natural Science Foundation of Shandong Province and the National Natural Science Foundation of China. (Source: China Science News, Liao Yang, Kong Fengru)

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