Nanopore confinement for electrochemical sensing at the single-molecule level

Single-molecule sensing opens avenues of studying the population heterogeneities and the conformational dynamics of system ranging from single DNAs to single proteins. Nanopores providing the electrochemically confined space for accommodation of single analytes, directly convert the single-molecule behaviors into the measurable electrochemical read-outs with high signal-to-noise ratio. A good volume of researches exists on nanopore-based electrochemical detection ranging from nucleic acids, peptides, proteins, and biomolecular complexes to organic polymers and small molecules. Due to the advantage of nanopore confinement, new sensing mechanisms have been reported to shed light on single-molecule structure and activity correlation. In this review, we provide an overview of the electrochemically confined effects in a nanopore on the aspects ranging from single-molecule volume exclusion, redox process confinement, and electromagnetic field enhancement. The electrochemically confined effects would provide nanopore a series of vivid and exciting discoveries in single-molecule analysis of biological processes and chemical reactions.