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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]

This work reports a surface acoustic wave (SAW) DNA sensor that synergizes the surface mass effect for signal-amplified and sequence-specific DNA detection in blood serum. By combining an enzyme-mediated DNA extension reaction (both viscoelastic and mass fractions) with the in situ synthesis of silver nanoparticles (mass fraction), a highly sensitive SAW biosensing interface with synergistic mass loading was tailor-engineered. As target DNA hybridized with the surface-confined capture probes, the exposed 3′-OH terminal of the target sequence could be triggered to elongate in the presence of terminal deoxynucleoside transferase (TdT) and deoxy-ribonucleoside triphosphate (dNTP), thereby producing an evident mass effect. Importantly, the extended domain can serve as a template to specifically hybridize with Ag+-binding sequences. In the presence of reducing agents, the accumulated silver ions would nucleate for the in situ synthesis of silver nanoparticles, further enhancing the mass loading. By using this approach, we observed a rapid growth event of silver nanoparticles for signal enhancement, which improved the detection limit (0.8 pM) of the SAW sensor by 3 orders of magnitude as compared to the strategy without signal amplification (at the nanomolar level). The sensor also achieved a high specificity in discriminating even a single-mismatched DNA sequence, and meanwhile could probe the low-abundance DNA molecules directly in human serum with minimal interference. These advantages make the SAW biosensor promising for practical applications, such as monitoring of molecular interactions and disease diagnostics. [ABSTRACT FROM AUTHOR]

Na2.65Ti3.35Fe0.65O9 rods were prepared by a simple solid-state route and coated with carbon to enhance their electronic conductivity. For the first time, Na2.65Ti3.35Fe0.65O9 was explored as an anode material for Na-ion batteries to deliver a discharge capacity of 137.5 mA h g−1 at a current rate of 40 mA g−1. The charge/discharge capacity of a carbon-coated sample increased by 46.3% to achieve 201.1 mA h g−1. [ABSTRACT FROM AUTHOR]

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.

Na(2.65)Ti(3.35)Fe(0.65)O9 rods were prepared by a simple solid-state route and coated with carbon to enhance their electronic conductivity. For the first time, Na(2.65)Ti(3.35)Fe(0.65)O9 was explored as an anode material for Na-ion batteries to deliver a discharge capacity of 137.5 mA h g(-1) at a current rate of 40 mA g(-1). The charge/discharge capacity of a carbon-coated sample increased by 46.3% to achieve 201.1 mA h g(-1).