Quantification of Intracellular Proteins in Single Cells Based on Engineered Picoliter Droplets

Unlike conventional bulk measurements, single-cell protein analysis permits quantification of protein expression in individual cells. This has shed light on the cell-to-cell variation in heterogeneous biological systems, such as solid tumors, brain tissues, and developing embryos. Herein, a microfluidic method is developed to profile protein expression in individual cells by performing single-cell intracellular protein immunoassay in pico -liter paired droplets. The high sensitivity of single-cell protein analysis on a chip is achieved by the confined reaction volume of picoliter droplets, efficient kinetic characteristics of the immuno-assay through active mixing, and minimum single-cell protein loss by integrated operations. The abundance of an intracellular prostate specific antigen at the single-cell level is measured, and then the platform is applied to identify cell types and investigate heterogeneity within cell populations. Overall, a paired chip for single-cell immunoassay establishes a foundation for parallel, sensitive, and integrated protein quantification at the single-cell level and will find wide applications in the field of single-cell proteomics.

Automated summary

Single-cell protein analysis allows for quantification of protein expression in individual cells, shedding light on cell-to-cell variation in heterogeneous biological systems. A microfluidic method has been developed to profile protein expression in individual cells using paired droplets, achieving high sensitivity and minimal protein loss. This platform can identify cell types and investigate heterogeneity within cell populations, establishing a foundation for parallel, sensitive, and integrated protein quantification at the single-cell level.