Microfluidic Quantitative Flow Cytometer With Light Modulation

Abstract

Quantitative detections of proteins for single cells have made great contributions to tumor heterogeneity and immune variance while effective tools of measuring single-cell intracellular proteins are under developments. This study reported a flow cytometer based on constriction microchannel and light modulation, which was capable of quantifying intracellular proteins for single cells with high resolution. Cells tagged with fluorescein labelled antibodies were squeezed into the constriction microchannel as either the calibration or detection structure where a light source with a carrier wave was used for fluorescent modulation, which was further demodulated into the low-frequency domain and translated into numbers of single-cell proteins. In platform characterization, the inclusion of light modulation was shown to effectively improve the detection resolution from &#x007E;1000 intracellular proteins per cell without modulation to &#x007E;100 intracellular proteins per cells with modulation. As demonstrations, expressions of mutant p53 or phosphorylated p53 from tens of thousands of single T47D and/or A431 cells were quantitatively measured by the microfluidic quantitative flow cytometer, which were 1.78 &#x00B1; <inline-formula> <tex-math notation="LaTeX">$0.96 \times10$ </tex-math></inline-formula>⁵ mutant p53 per cell for T47D cells (<inline-formula> <tex-math notation="LaTeX">${N}_{c} =10\,315$ </tex-math></inline-formula>), 1.99 &#x00B1; <inline-formula> <tex-math notation="LaTeX">$1.49\times10$ </tex-math></inline-formula>⁵ mutant p53 per cell for A431 cells (<inline-formula> <tex-math notation="LaTeX">${N}_{c} =15\,665$ </tex-math></inline-formula>), and 6.34 &#x00B1; <inline-formula> <tex-math notation="LaTeX">$7.50\times10$ </tex-math></inline-formula>³ phosphorylated p53 per cell for A431 cells treated with doxorubicin (<inline-formula> <tex-math notation="LaTeX">${N}_{c} =12\,812$ </tex-math></inline-formula>). In conclusion, the inclusion of light modulation can effectively decrease electrical and optical noises and therefore improve detection resolution in microfluidic quantitative flow cytometry.