Quantitative
information about protein–ligand interactions
is central to drug discovery. To obtain the quintessential reaction
dissociation constant, ideally measurements of reactions should be
performed without perturbations by molecular labeling or immobilization.
The technique of transient induced molecular electrical signal (TIMES)
has provided a promising technique to meet such requirements, and
its performance in a microfluidic environment further offers the potential
for high throughput and reduced consumption of reagents. In this work,
we further the development by using integrated TIMES signal (i-TIMES)
to greatly enhance the accuracy and reproducibility of the measurement.
While the transient response may be of interest, the integrated signal
directly measures the total amount of surface charge density resulted
from molecules near the surface of electrode. The signals enable quantitative
characterization of protein–ligand interactions. We have demonstrated
the feasibility of i-TIMES technique using different biomolecules
including lysozyme, N,N′,N″-triacetylchitotriose (TriNAG), aptamer, p-aminobenzamidine (pABA), bovine pancreatic ribonuclease
A (RNaseA), and uridine-3′-phosphate (3′UMP). The results
show i-TIMES is a simple and accurate technique that can bring tremendous
value to drug discovery and research of intermolecular interactions.