Microchip Cytometry for Multiplexed Single-Cell Protein Detection in a Low-Resource Setting toward Point of Care Diagnosis.

Multiplex measurement of protein expression with the single-cell resolution has been challenging. Although a few conventional approaches including flow cytometry and immunofluorescence-based methods have been developed to detect proteins in individual cells, they are either dependent on bulky instrument or not multiplexed and high-throughput enough. Here we present a portable single-cell analysis system that is operable in a resource-limited environment. A stand-sit microchip housed in a clamp enables simple and instrument-free operation of all necessary steps, and the detection based on immunogold enhancement exonerates the reliance on fluorescence optics and electronics. The quantified sensitivity was found comparable to the conventional fluorescence approaches. We used this system to analyze five immune effector proteins and found the system is equally effective to detect those proteins in hundreds of single cells. Significant increase of cytokine protein production by THP1 monocytes was observed upon stimulation by lipopolysaccharide. Further study showed that a low-end imaging setup with low resolution can also detect signals without much loss of sensitivity. Taken together, this portable multiplex single-cell system may find broad biomedical applications in a field setting.