Single microentity analysis-based ultrasensitive bioassays: Recent advances, applications, and perspectives

The development of ultrasensitive biomarker analysis strategies is of great significance in early disease diagnosis and human health. Superior to the conventional homogenous bulk measurements, single entity analysis-based bioassays are of higher sensitivity and have the potential to detect single biomarker heterogeneities. Among them, the ones based on the single microentity analysis have attracted much attention because they are easily operated and suitable to be monitored with varieties of detection instruments. In this review, we focus on the single microentity analysis-based bioassays, and categorize them as analog assays and digital assays by taking the biomarker to microentity ratios, the distribution modes of targets on the microentities, as well as the mechanism for signal generation/readout into consideration. We have systematically introduced the design principles, the analytical performance, the advantages and the challenges of these techniques. In the end, the opportunities and future trends in this field are highlighted.