Quantum dots for electrochemical cytosensing

Quantum dots (QDs), with confined size on the nanoscale (1–10 nm), are usually made of II−VI B group or III−V A group elements or their alloyed semiconductor materials. QDs are endowed with prominent electrochemical and photophysical properties, which makes QD-based assays powerful probes for electrochemical bioanalysis. Both excellent signal enhancement and functionalization have been explored and further developed. In this review, we start by briefly introducing the electrochemical and photophysical characteristics of QDs. Next, the mechanism of QDs for electrochemical cell analysis is systematically stated and critically reviewed from the three aspects of the main components, mechanism, and principle of QD-based electrochemistry (EC), electrochemiluminescence (ECL) and photoelectrochemistry (PEC) cytosensing, individually. The main context will focus on the critical comparison of advantages and disadvantages, similarities, and differences among EC, ECL and PEC. In addition, we summarize selected articles from 2017 to 2021 on QD-based electrochemical cytosensors and discuss the different detection abilities of specific targets, including quantitative cell detection, cell surface biomarkers, cell metabolism, and single-cell analysis.