Nanofluidic Aptamer Nanoarray to Enable Stochastic Capture of Single Proteins at Normal Concentrations

Abstract Single‐molecule experiments allow understanding of the diversity, stochasticity, and heterogeneity of molecular behaviors and properties hidden by conventional ensemble‐averaged measurements. They hence have great importance and significant impacts in a wide range of fields. Despite significant advances in single‐molecule experiments at ultralow concentrations, the capture of single molecules in solution at normal concentrations within natural biomolecular processes remains a formidable challenge. Here, a high‐density, well‐defined nanofluidic aptamer nanoarray (NANa) formed via site‐specific self‐assembly of well‐designed aptamer molecules in nanochannels with nano‐in‐nano gold nanopatterns is presented. The nanofluidic aptamer nanoarray exhibits a high capability to specifically capture target proteins (e.g., platelet‐derived growth factor BB; PDGF‐BB) to form uniform protein nanoarrays under optimized nanofluidic conditions. Owing to these fundamental features, the nanofluidic aptamer nanoarray enables the stochastic capture of single PDGF‐BB molecules at a normal concentration from a sample with an ultrasmall volume equivalent to a single cell by following Poisson statistics, forming a readily addressable single‐protein nanoarray. This approach offers a methodology and device to surpass both the concentration and volume limits of single‐protein capture in most conventional methodologies of single‐molecule experiments, thus opening an avenue to explore the behavior of individual biomolecules in a manner close to their natural forms, which remains largely unexplored to date.