Reactive oxygen species (ROS)‐based therapeutic strategies play an important role in cancer treatment. However, in situ, real‐time and quantitative analysis of intracellular ROS in cancer treatment ...for drug screening is still a challenge. Herein we report one selective hydrogen peroxide (H2O2) electrochemical nanosensor, which is prepared by electrodeposition of Prussian blue (PB) and polyethylenedioxythiophene (PEDOT) onto carbon fiber nanoelectrode. With the nanosensor, we find that the level of intracellular H2O2 increases with NADH treatment and that increase is dose‐dependent to the concentration of NADH. High‐dose of NADH (above 10 mM) can induce cell death and intratumoral injection of NADH is validated for inhibiting tumor growth in mice. This study highlights the potential of electrochemical nanosensor for tracking and understanding the role of H2O2 in screening new anticancer drug.
A H2O2‐selective nanoelectrode is reported to monitor the dynamics of H2O2 produced by NADH treatment, indicating the potential tumor suppressor role of NADH. This work not only provides a potential therapeutic strategy for cancer therapy, but also offers a powerful technique to screen the cancer treatment.
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Alternative energy conversion systems with high efficiency, low cost and environmental benignity attract increasing attention. Herein, we astonishedly found that one new M-Nx complex, ...cobalt corrole Co(tpfc)(py)2 (where, tpfc=5,10,15-tris(pentafluorophenyl) corrole and py=pyridine, denoted as Co-TPFC), adsorbed on the surface of multi-walled carbon nanotube (MWNT) (namely, Co-TPFC/MWNT) displayed an outstanding electrocatalytic property towards the reduction of oxygen (O2). The resultant electrocatalyst Co-TPFC/MWNT without pyrolysis treatment or covalent binding demonstrated a direct 4e reduction of O2 to water in acid media, while producing the 2e reduction product of H2O2 in a minimal amount. Meanwhile, our catalyst exhibited better long-term durability and higher tolerance to methanol compared to commercially used high-cost Pt/C catalyst. These results suggest that the Co-TPFC/MWNT catalyst is a technologically promising candidate for practical applications in metal-air batteries and fuel cells.
In vivo electrochemistry with a carbon-fiber electrode (CFE) is the most useful method for tracking neurochemicals in specific brain regions due to its high spatiotemporal resolution. However, CFE is ...inevitably subject to surface biofouling that leads to a decrease in sensitivity. Here, we develop a polytannic acid (PTA)-doped nanoporous conductive polyaniline (PANI) membrane-coated CFE to minimize biofouling-induced negative effects for in vivo analysis. The as-prepared PTA–PANI-coated CFE shows excellent antifouling property and enrichment capacity toward electrochemical measurement of dopamine (DA) in physiological pH. The PTA–PANI-coated CFE can in vivo monitor the release of DA induced by electrical stimulation and exhibits almost the same sensitivity in the postcalibration (S post) and the precalibration (S pre; S post/S pre = 0.90). We believe this conductive nanoporous membrane-coated CFE offers a new platform for in vivo measurement, which would help probe brain chemistry.
Hydrogen sulfide (H2S) plays a pivotal role in gas signal transduction, neuroprotection, and regulation of physiological and pathological processes. However, in vivo tracking the dynamic of hydrogen ...sulfide in the complex brain environment still faces huge challenges. This study demonstrates a new potentiometric method to monitor in vivo the dynamics of hydrogen sulfide in the rat brain using silver nanoparticles (AgNPs)-modified carbon fiber microelectrodes (AgNPs/CFE) pretreated with Na2S (i.e., Ag2S/AgNPs/CFE), which acts as a solid-contact and ion-selective microelectrode. The Ag2S/AgNPs/CFE exhibits good potential response toward hydrogen sulfide in the range of 2.5–160 μM, with a detection limit of 0.8 μM. Because of the presence of Ag2S, the Ag2S/AgNPs/CFE shows good selectivity to hydrogen sulfide, avoiding the interference from coexistent electroactive neurochemicals and the analogies, such as ascorbic acid and cysteine in the central nervous system. This good selectivity combined with the reversibility, protein antifouling, and biocompatibility of the microelectrode enables the Ag2S/AgNPs/CFE to detect hydrogen sulfide in the rat brain during local microinfusion of Na2S and the change in pH. Our study provides a reliable method to track hydrogen sulfide selectively in vivo, which will help to explore the function of hydrogen sulfide in neurophysiology and pathology.
Spreading depolarization (SD) is one of the most common neuropathologic phenomena in the nervous system, relating to numerous diseases. However, real‐time monitoring the rapid chemical changes during ...SD to probe the molecular mechanism remains a great challenge. We develop a potentiometric dual‐channel microsensor for simultaneous monitoring of H2S and pH featuring excellent selectivity and spatiotemporal resolution. Using this microsensor we first observe real time changes of H2S and pH in the rat brain induced by SD. This changes of H2S are completely suppressed when the rat pre‐treats with aminooxyacetic acid (AOAA), a blocker to inhibit the H2S‐producing enzyme, indicating H2S fluctuation might be related to enzyme‐dependent pathway during SD and less pH‐dependent. This study provides a new perspective for studying the function of H2S and the molecular basis of SD‐associated diseases.
Understanding the mechanism of spreading depolarization (SD) is essential for the therapy of SD associated diseases. We report a potentiometric dual‐channel microsensor for simultaneous detection of H2S and pH, enabling the first observation of H2S fluctuation induced by SD in vivo. Our work provides the direct experimental evidence that the H2S release during SD in rat cortex is less pH‐dependent, possibly by modulating enzyme‐dependent pathways.
Passivation of electrodes caused by nonspecific adsorption of protein can dramatically reduce sensing sensitivity and accuracy, which is a great challenge for in vivo neurochemical monitoring. ...However, most antipassivation strategies are not suitable to carbon fiber microelectrodes (CFMEs) for in vivo measurement, and these methods also do not work on electrochemical biosensors that fix biometric elements. In this study, we demonstrate that chitosan hydrogel-coated microelectrodes can avoid the current passivation caused by protein adsorption on the surface of carbon fiber because the chitosan hydrogel prepared by local pH gradient caused by hydrogen evolution reaction has three-dimensional networks containing large amounts of water. The highly hydrophilic three-dimensional structure of hydrogel not only forms a biocompatible interface to confine enzymes but also keeps the fast mass transfer of analytes, such as dopamine, ascorbic acid, and glucose. The consistency of the precalibration and postcalibration of the prepared sensor enables in vivo amperometric detection of both electroactive species based on their redox property and electroinactive species based on the enzyme. This study provides a simple and versatile strategy to constitute an amperometric sensor interface to resist passivation of protein adsorption in a complex biological environment such as the brain.
Challenges remain in establishing a universal method to precisely tune electrochemical properties of conducting polymers for multifunctional neurosensing with high selectivity and sensitivity. Here, ...we demonstrate a facile and general approach to achieving synergistic charge percolation in conducting polymers (i.e., poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS) by incorporating conductive catalysts (i.e., carbon nanotubes, CNTs) and post‐processing. The approach shows synergistic effects: (i) CNTs and post‐processing together promote PEDOT ordered interconnection for highly efficient charge percolation that accelerates electrochemical kinetics; (ii) CNTs catalyze the electrooxidation of vitamin C for selective electrochemical sensing; (iii) CNTs enhance the charge storage/injection capacity of PEDOT:PSS. The prepared CNT‐PEDOT:PSS fiber mechanically matches with neural tissues and is proved to be a biocompatible versatile microsensor capable of high‐performance neurosensing in vivo.
We report a universal approach that endows conducting polymer (PEDOT:PSS)‐based fiber‐microsensors with an interiorly constructed synergistic charge percolation highway for (i) selective and sensitive sensing of a target neurochemical (vitamin C) and (ii) high‐fidelity sensing of neuronal activities. This strategy is validated through in vivo applications in the nervous system.
Wearable pressure sensors have attracted increasing attention for biomechanical monitoring due to their portability and flexibility. Although great advances have been made, there are no facile ...methods to produce sensors with good performance. Here, we present a simple method for manufacturing flexible and self-powered piezoelectric sensors based on LiNbO3 (LN) particles. The LN particles are dispersed in polypropylene (PP) doped with multiwalled carbon nanotubes (MWCNTs) by hot pressing (200 °C) to form a flexible LN/MWCNT/PP piezoelectric composite film (PCF) sensor. This cost-effective sensor has high sensitivity (8 Pa), fast response time (ca. 40 ms), and long-term stability (>3000 cycles). Measurements of pressure changes from peripheral arteries demonstrate the applicability of the LN/MWCNT/PP PCF sensor to biomechanical monitoring as well as its potential for biomechanics-related clinical diagnosis and forecasting.
Spreading depolarization (SD) is one of the most common neuropathologic phenomena in the nervous system, relating to numerous diseases. However, real-time monitoring the rapid chemical changes during ...SD to probe the molecular mechanism remains a great challenge. We develop a potentiometric dual-channel microsensor for simultaneous monitoring of H
S and pH featuring excellent selectivity and spatiotemporal resolution. Using this microsensor we first observe real time changes of H
S and pH in the rat brain induced by SD. This changes of H
S are completely suppressed when the rat pre-treats with aminooxyacetic acid (AOAA), a blocker to inhibit the H
S-producing enzyme, indicating H
S fluctuation might be related to enzyme-dependent pathway during SD and less pH-dependent. This study provides a new perspective for studying the function of H
S and the molecular basis of SD-associated diseases.
In vivo electrochemical analysis is of great significance in understanding the dynamics of various physiological and pathological activities. However, the conventional microelectrodes for ...electrochemical analysis are rigid and permanent, which comes with increased risks for long-term implantation and secondary surgery. Here, we develop one biodegradable microelectrode for monitoring the dynamics of extracellular Ca2+ in rat brain. The biodegradable microelectrode is prepared by sputtering gold nanoparticles (AuNPs) on a wet-spun flexible poly(l-lactic acid) (PLLA) fiber for conduction and transduction and coating a Ca2+ ion-selective membrane (ISM) with a PLLA matrix on the PLLA/AuNPs fiber, forming PLLA/AuNPs/Ca2+ISME (ISME = ion-selective microelectrode). The prepared microelectrode shows excellent analytical properties including a near-Nernst linear response toward Ca2+ over the concentration range from 10 μM to 50 mM, good selectivity, and long-term stability for weeks as well as biocompatibility and biodegradability. The PLLA/AuNPs/Ca2+ISME can monitor the dynamics of extracellular Ca2+ following spreading depression induced by high potassium even if in the fourth day. This study provides a new design strategy for the biodegradable ISME and promotes the development of biodegradable microelectrodes for long-term monitoring of chemical signals in brain.
