Novel Self-Calibrating Amperometric and Ratiometric Electrochemical Nanotip Microsensor for pH Measurement in Rat Brain

Abstract

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.

Multiplexed optical fiber sensors for dynamic brain monitoring

“…33,34 pH also serves as an indicator of TBI, whereby a reduction of pH is observed because of disrupted anaerobic metabolism and increased acetic acid. 35 To date, several approaches have been developed to follow the progress of brain diseases for brain pH monitoring, including fluorescence spectroscopy, 36,37 electrochemical sensing, 38 and colorimetric sensing. 39 In this study, the determination of pH in aCSF is based on the colorimetric property of a pH sensing film at the fiber tip.…”

“…These characterization studies on the designed optical sensors have demonstrated good sensing performance of the sensors for brain pH, temperature, DO, and glucose sensing. Compared with commercially available devices for brain monitoring (MRI, MD) or the state-of-the-art EC sensors, 14,38,40 the proposed multiplexed sensing sensors achieved comparable sensitivity, reversibility, stability, and selectivity. In terms of implantable diagnosis, optical sensors could also provide battery-free and remote sensing, and they can be easily miniaturized.…”

A self-ratiometric and selective electrochemical sensor for the detection of tyrosinase in mouse brain homogenate

“…An electrochemical method with high selectivity can easily realize the real-time and continuous measurement of tissue amino acids, reactive oxygen species (ROS) and neurotransmitters. [14][15][16][17][18] Considering the advantages of electrochemical methods, a reliable Tyr electrochemical sensor is desirable to deeply distinguish and understand the differences of Tyr in normal and pathological environments. However, as far as we know, no electrochemical sensor has been developed for the determination of Tyr in a brain-related biological environment.…”

Dual-Mode Ratiometric Electrochemical and Turn-On Fluorescent Detection of Butyrylcholinesterase Utilizing a Single Probe for the Diagnosis of Alzheimer’s Disease

“…However, ratiometric designs necessitate the separate mixing of multiple components, which complicates the manufacturing process. The development of single-component ratiometric sensors has been performed for this purpose. − Tian et al, for example, designed and synthesized Hemin-Fc, which consisted of an amide bond connecting a hemin group to two aminoferrocene molecules. The hemin group acts as a recognition unit for O 2 , and the Fc group can act as an internal reference for ratiometric biosensing since its current and potential signals remain nearly constant with variations in O 2 , thereby providing an in-built correction .…”

“…The hemin group acts as a recognition unit for O 2 , and the Fc group can act as an internal reference for ratiometric biosensing since its current and potential signals remain nearly constant with variations in O 2 , thereby providing an in-built correction . Recently, our group developed a ratiometric electrochemical sensor for in situ pH detection; in this sensor, pH-responsive poly- o -phenylenediamine molecules were deposited via in situ electrochemical polymerization without the use of a reference molecule. Using the electrochemical latent redox ratiometric probes NABFC and ABFC, Manibalan et al developed a novel electrochemical assay platform for monitoring H 2 S production in real-time by living cells ( E. coli ) .…”