Overview of Raman-Assisted Cell Sorting (RACS)

Raman-Assisted Cell Sorting (RACS) integrates Raman spectroscopy with microfluidics to achieve non-destructive, label-free sorting of cells based on their biochemical properties. Raman spectroscopy is a non-invasive technique that analyzes the vibrational frequencies of molecules, revealing detailed information about their chemical composition. This label-free method uniquely links the phenotypic functions of cells with their genotypic characteristics.

One major challenge in cell sorting is the high-throughput isolation of viable cells from complex mixtures. Traditional methods often rely on “trap-and-release” techniques, which are limited by factors such as weak Raman signals, cell size, medium conductivity, refractive index, and flow rate.

To address these limitations, we introduce a trapping-free RACS system that uses 3D hydrodynamic flow focusing. This system enables continuous and automated sorting of individual cells based on their Raman spectra. Our all-in-one setup is designed to precisely divert cells according to their biochemical signatures, offering a more efficient and effective solution for complex cell sorting tasks.

Comparison to Fluorescence-Activated Cell Sorting (FACS)

• Labeling: RACS is a label-free technique that sorts cells based on intrinsic biochemical properties, while FACS relies on external fluorescent labels or antibodies to differentiate cells.
• Non-Destructive: RACS is non-destructive, maintaining cell viability by avoiding chemical or physical labeling, whereas FACS may affect cell integrity due to labeling processes.
• Specificity: RACS provides high specificity by analyzing the unique Raman spectra of cells, capturing detailed molecular information. In contrast, FACS relies on the presence of specific markers, which may not always represent the complete biochemical profile.
• Throughput: While FACS is renowned for its high throughput, RACS, particularly with 3D hydrodynamic flow focusing, offers significant improvements in sorting efficiency, although it may still lag behind FACS in terms of processing speed.
• Applications: RACS is particularly advantageous in applications requiring detailed biochemical analysis and preservation of cell function, while FACS is more commonly used in scenarios where high-speed sorting and identification of surface markers are essential.