Microfluidic Digital ELISA towards Single Cell Analysis

Abstract

Cell-to-cell heterogeneity predicts a multitude of functions for homeostasis and development of disease states. These minute variations can make a massive impact in understanding the main components involved in a disease such as cancer. Tracking the protein expression in single cells is in great need as they enable the study of heterogeneous behaviors, but the main challenges are the requirement of the methodologies that are sensitive enough to detect low copy number of protein molecules within a wide dynamic range. Low copy proteins cannot be neglected as they can provide information about the phenotypic responses involved. Moreover, traditional analog methods are not suitable for detecting such small numbers as they give an average measurement, differentiating unique cells and quantifying population distributions would be problematic. Digital immunoassays have emerged as a robust technology for ultrasensitive detection of proteins. Here we engineered a multiplexed microfluidic digital ELISA platform with microarray structures for analyzing multiple proteins with low sample volume and high sensitivity. Cross communication between individual reactions, diffusing of reagents into bulk solutions and evaporation of solvents could be critical. To address this concern, we have developed a portable, automated instrument for sealing the microwells in the chambers with high pressure for conducting chemi- fluorescent reactions with increased resolution and sensitivity. With our developed platform, we can detect up to 15 biomarkers. We also applied our digital platforms for the detection of PSA aptamer with biotinylated lectins.