Electrochemical Analysis of Single Glucose Oxidase with a Nanopipette

Nanopore-based electrochemical technique is a promising tool for detecting single proteins. However, detecting single proteins using a nanopipette in their native state without labeling is challenging due to the rapid translocation, which results in an inefficient signal identification. In our study, we finely tuned the driving force equilibrium between electrophoretic force (EPF) and electroosmotic flow (EOF) inside the nanopipette for efficient sensing of single glucose oxidase (GOD) molecules. The duration time of GOD within the nanopipette is extended to about 4 ms. This strategy provided clear ionic current signals with a signal-to-noise ratio of 3.3. As EPF increased in the direction opposite to the motion of GOD, we observed a nonlinear growth in GOD’s duration time. This extended the duration to about 4.4 times longer at −1000 mV compared to at −800 mV. Hence, nanopore-based electrochemical sensing could be used for single GOD molecule analysis as an ultrasensitive method.