Dynamic Single-Molecule Sensors: A Theoretical Study

One of the key advantages of single-molecule sensors over conventional ensemble technologies is their capability of revealing the heterogeneity among molecular events. In dynamic single-molecule sensing, heterogeneity in molecular interaction kinetics is quantified as the fingerprint to specifically detect target molecules. This strategy offers a unique approach to develop ultrasensitive biosensors with a limit of detection at the fM level, which is three orders of magnitude lower than that of conventional assays. However, due to the lack of a comprehensive theoretical model, the rational design of dynamic single-molecule sensors is challenging. Herein, we present the theoretical study of sensing performance with a hydrodynamic model. We quantitatively show that there is a dilemma regarding the probe design. High-affinity probes offer higher specificity but require extremely long assay time, while low-affinity probes could shorten the assay time but are prone to the interference from unwanted molecules. This study also suggests that one possible solution to solve this dilemma is by applying external disturbance to the system, as we have recently demonstrated by experiments. We anticipate that this work could inspire the rational design of single-molecule sensors to further improve the sensitivity, specificity, and multiplexing capability.