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Monitoring the dynamic pH changes in vivo remains very essential to comprehend the function of pH in various physiological processes. In this study, we report a high-performance electrochemical pH microneedle based on an acupuncture needle (AN) for real-time monitoring of pH changes in a rat brain. The pH microneedle was prepared by a layer-to-layer assembly of molybdenum disulfide (MoS2) nanosheets and polyaniline (PAN), with an attempt to achieve a highly sensitive detection of hydrogen ions (H+). The as-prepared PAN/MoS2/AN exhibited a high Nernstian response of −51.2 mV per pH over a wide pH range from 3.0 to 9.0, and excellent selectivity toward pH against other potential interfering species in the brain. Moreover, the corresponding open circuit potential rapidly increased and decreased when Na2CO3 or NaH2PO4 was injected into the rat brain, respectively, demonstrating that the PAN/MoS2/AN has an excellent response toward pH changes in vivo. This work provides a new potentiometric method for real-time monitoring of dynamic pH changes in vivo with high reliability and stability. [ABSTRACT FROM AUTHOR]

This work describes the adaptive use of a conventional stainless steel acupuncture needle as the electrode substrate for construction of a molybdenum disulfide (MoS2) and platinum nanoparticles (PtNPs) layer-modified microneedle sensor for real-time monitoring of hydrogen peroxide (H2O2) release from living cells. To construct the nanocomposite-functionalized microneedle, the needle surface was first coated with a gold film by ion sputtering to enhance the conductivity. Subsequently, an electrochemical deposition method was successfully employed to deposit MoS2 nanosheet and Pt nanoparticles on the needle tip as the sensing interface. Electrochemical study demonstrated that the MoS2/PtNPs nanocomposite-modified needle exhibited excellent catalytic performance and low over-potential toward the reduction of H2O2. Not only did the microneedle achieve a wide linear range from 1 to 100 μmol L−1 with a limit of detection down to 0.686 μmol L−1, but it also realized the highly specific detection of H2O2. Owing to these remarkable analytical advantages, the prepared microneedle was applied to determine H2O2 release from living cells with satisfactory results. The MoS2/PtNPs nanocomposite-functionalized microneedle sensor is simple and affordable, and can serve as a promising electrochemical nonenzymatic sensing platform. Moreover, this superfine needle sensor shows great potential for real-time monitoring of reactive oxygen species in vivo with minimal damage. [ABSTRACT FROM AUTHOR]

Au/CeO 2 was demonstrated to be a high efficiency catalyst for the conversion of 2-phenoxyacetophenol (PP-ol) employing O 2 as an oxidant and methyl alcohol as the solvent without using an erosive strong base or acid. Mechanistic investigations, including emission quenching experiments, electron spin-resonance (ESR) and intermediate verification experiments, were carried out. The results verified that the superoxide anion activated by Au/CeO 2 from molecular oxygen plays a vital role in the oxidation of lignin model compounds, and the cleavage of both the β-O-4 and C α -C β linkages was involved. Au/CeO 2 also performed well in the oxidative conversion of organosolv lignin under mild conditions (453 K), producing vanillin (10.5 wt%), methyl vanillate (6.8 wt%), methylene syringate (3.4 wt%) and a ring-opened product. Based on the detailed characterization data and mechanistic results, Au/CeO 2 was confirmed to be a promising catalytic system., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Monitoring the dynamic pH changes in vivo remains very essential to comprehend the function of pH in various physiological processes. In this study, we report a high-performance electrochemical pH microneedle based on an acupuncture needle (AN) for real-time monitoring of pH changes in a rat brain. The pH microneedle was prepared by a layer-to-layer assembly of molybdenum disulfide (MoS2) nanosheets and polyaniline (PAN), with an attempt to achieve a highly sensitive detection of hydrogen ions (H+). The as-prepared PAN/MoS2/AN exhibited a high Nernstian response of -51.2 mV per pH over a wide pH range from 3.0 to 9.0, and excellent selectivity toward pH against other potential interfering species in the brain. Moreover, the corresponding open circuit potential rapidly increased and decreased when Na2CO3 or NaH2PO4 was injected into the rat brain, respectively, demonstrating that the PAN/MoS2/AN has an excellent response toward pH changes in vivo. This work provides a new potentiometric method for real-time monitoring of dynamic pH changes in vivo with high reliability and stability.

This work describes the adaptive use of a conventional stainless steel acupuncture needle as the electrode substrate for construction of a molybdenum disulfide (MoS 2 ) and platinum nanoparticles (PtNPs) layer-modified microneedle sensor for real-time monitoring of hydrogen peroxide (H 2 O 2 ) release from living cells. To construct the nanocomposite-functionalized microneedle, the needle surface was first coated with a gold film by ion sputtering to enhance the conductivity. Subsequently, an electrochemical deposition method was successfully employed to deposit MoS 2 nanosheet and Pt nanoparticles on the needle tip as the sensing interface. Electrochemical study demonstrated that the MoS 2 /PtNPs nanocomposite-modified needle exhibited excellent catalytic performance and low over-potential toward the reduction of H 2 O 2 . Not only did the microneedle achieve a wide linear range from 1 to 100 μmol L -1 with a limit of detection down to 0.686 μmol L -1 , but it also realized the highly specific detection of H 2 O 2 . Owing to these remarkable analytical advantages, the prepared microneedle was applied to determine H 2 O 2 release from living cells with satisfactory results. The MoS 2 /PtNPs nanocomposite-functionalized microneedle sensor is simple and affordable, and can serve as a promising electrochemical nonenzymatic sensing platform. Moreover, this superfine needle sensor shows great potential for real-time monitoring of reactive oxygen species in vivo with minimal damage.