Photoactivated Bacteriorhodopsin/SiN_<i>x</i> Nanopore-Based Biological Nanofluidic Generator with Single-Protein Sensitivity.

Nanofluidics is an emerging hot field that explores the unusual behaviors of ions/molecules transporting through nanoscale channels, which possesses a broad application prospect. However, in situ probing bioactivity of functional proteins on a single-molecule level by a nanofluidic device has not been reported, and it is still a big challenge in the field. Herein, we reported a biological nanofluidic device with a single-protein sensitivity, based on natural proton-pumping protein, bacteriorhodopsin (bR), and a single SiNx nanopore. Nanofluidic single-molecule probing of bR proton-pumping activity and its light response were achieved under applied voltage of 0 V, by <i>biologically self-powered</i> steady-state ionic current nanopore sensing. Green-light irradiation of the device led to the monitoring of a steady-state proton current of ∼3.51 pA/per bR trimer, corresponding to charge density of 815 μC/cm² generated by each bR monomer, which far exceeded the previously reported value of 1.4 μC/cm². This finding and method would promote the development of artificial biological and hybrid nanofluidic devices in biosensing and energy conversion applications.