posted on 2021-10-05, 17:41authored byHui Dong, Le Zhao, Yanli Zhou, Xiuhua Wei, Cuicui Xu, Yintang Zhang, Maotian Xu
Brain pH has been proven to be a
key factor in maintaining normal
brain function. The relationship between local pH fluctuation and
brain disease has not been extensively studied due to lack of the
accurate in situ analysis technology. Herein, we have for the first
time proposed a voltammetric pH sensor by measuring the ratio of current
signals instead of the previously reported potential based on the
Nernst equation. Single-walled carbon nanotubes (CNT) were first self-assembled
on the electrode surface of a carbon-fiber nanotip electrode (CFNE).
Then, poly-o-phenylenediamine (PoPD) molecules were deposited as pH-responsive molecules through in
situ electrochemical polymerization. The compact CFNE/CNT/PoPD exhibited a good redox process with the on–off–on
ratiometric electrochemical response to pH ranging from 4.5 to 8.2,
providing self-correction for in situ pH detection. Thus, the proposed
sensor enabled the accurate measurement of pH with excellent selectivity
even in the presence of proteins or electroactive species. In addition,
the sensor showed high repeatability, reproducibility, and reversibility
in measuring pH and even demonstrated good stability when it was exposed
to air for 5 months. Finally, we successfully detected the fluctuation
of pH in rat brains with cerebral ischemia and rat whole blood. Overall,
this research not only provides a good tool for the detection of rat
brain pH but also provides a new strategy for further designing nanosensors
for intracellular or subcellular pH.