Microfluidic single-cell functional proteomics

We review an emerging microfluidic single-cell functional proteomics field and the associated technologies. Functional proteins, such as secreted signaling proteins from immune cells and phosphoproteins in cancer cells, refer to those that play important roles in promoting live cells’ physiological activities. Assay of single-cell functional proteins can be carried out by either cytometry or newly developed microfluidic tools, each of which possesses its own advantages and disadvantages. The use of microfluidic chips brings benefits of high multiplexity, low cost, and high flexibility to integrate various cell manipulation strategies into one platform, while such platforms are normally less developed and automated. We focus the discussion specifically on single-cell barcode technology, which has been more mature than others, and is able to quantitate up to 42 different functional proteins from single cells. This platform has also been uniquely extended to the study of cell-cell interactions. Quantitative analysis of the single-cell functional proteins offers new perspectives of biological systems and provides a conduit between biology and the physicochemical laws. And finally we discuss the challenges and future of the microfluidic single-cell functional proteomics field.