Nanoelectrodes allow precise and quantitative measurements of important biological processes at the single living-cell level in real time. Cylindrical nanowire electrodes (NWEs) required for intracellular measurements create a great challenge for achieving excellent electrochemical and mechanical performances. Herein, we present a facile and robust solution to this problem based on a unique SiC-core-shell design to produce cylindrical NWEs with superior mechanical toughness provided by the SiC nano-core and an excellent electrochemical performance provided by the ultrathin carbon shell that can be used as such or platinized. The use of such NWEs for biological applications is illustrated by the first quantitative measurements of ROS/RNS in individual phagolysosomes of living macrophages. As the shell material can be varied to meet any specific detection purpose, this work opens up new opportunities to monitor quantitatively biological functions occurring inside cells and their organelles.

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The existence of a homeostatic mechanism regulating reactive oxygen/nitrogen species (ROS/RNS) amounts inside phagolysosomes has been invoked to account for the efficiency of this process but could not be unambiguously documented. Now, intracellular electrochemical analysis with platinized nanowire electrodes (Pt‐NWEs) allowed monitoring ROS/RNS effluxes with sub‐millisecond resolution from individual phagolysosomes impacting onto the electrode inserted inside a living macrophage. This shows for the first time that the consumption of ROS/RNS by their oxidation at the nanoelectrode surface stimulates the production of significant ROS/RNS amounts inside phagolysosomes. These results establish the existence of the long‐postulated ROS/RNS homeostasis and allows its kinetics and efficiency to be quantified. ROS/RNS concentrations may then be maintained at sufficiently high levels for sustaining proper pathogen digestion rates without endangering the macrophage internal structures.

Flexible electrochemical (EC) sensors have shown great prospect in epidermal detection for personal healthcare and disease diagnosis. However, no reports have been seen in flexible device for urea analysis in body fluids. Herein, we developed a flexible wearable EC sensor based on surface molecularly imprinted nanotubes for noninvasive urea monitoring with high selectivity in human sweat. The flexible EC sensor was prepared by electropolymerization of 3,4-ethylenedioxythiophene (EDOT) monomer on the hierarchical network of carbon nanotubes (CNTs) and gold nanotubes (Au NTs) to imprint template molecule urea. This sensor exhibited a good linear response toward physiologically relevant urea levels with negligible interferences from common coexisting species. Bending test revealed that this sensor possessed excellent mechanical tolerance and its EC performance was almost not affected by bending deformation. On-body results of human subjects showed that the flexible platform could distinctly respond to the urea levels in volunteer's sweat after aerobic exercise. The new flexible epidermal EC sensor can provide useful insights into noninvasive monitoring of urea levels in various biofluids, which is promising in the clinical diagnosis of diverse biomedical applications.

Nanoelectrodes allowp recise and quantitative measurements of important biological processes at the single living-cell level in real time.C ylindrical nanowire electrodes (NWEs) required for intracellular measurements create agreat challenge for achieving excellent electrochemical and mechanical performances.H erein, we present af acile and robust solution to this problem based on au nique SiC-core-shell design to produce cylindrical NWEs with superior mechanical toughness provided by the SiC nano-core and an excellent electrochemical performance provided by the ultrathin carbon shell that can be used as such or platinized. The use of such NWEs for biological applications is illustrated by the first quantitative measurements of ROS/RNS in individual phagolysosomes of living macrophages.Asthe shell material can be varied to meet any specific detection purpose,this work opens up new opportunities to monitor quantitatively biological functions occurring inside cells and their organelles.Numerous fundamental biological processes occur in subcellular locations and inside intracellular organelles.H ence, there is increased interest for monitoring and quantifying such processes in real time.I nt his respect, nanoelectrodes have many unique advantages in terms of selectivity and sensitivity.Quantitative detection of biochemical signals with very high spatial (ca. fL) and temporal resolution (ca. ms-ms) may report about only af ew thousand molecules with minimal invasion while maintaining cell viability. [1] Hence, nanoelectrodes have been designed for investigating many subcellular questions such as mapping exocytotic hot spots on plasma membranes, [2] single synapse behavior, [3] and monitor-ing intracellular events. [4] However,t he shapes of such nanoelectrodes mostly rely on needle-or disk-type patterns. However,s uch designs present severe limitations such as difficulties in allowing further modification [4c] or achieving high aspect ratio shafts because of the mechanical fragility of electroactive materials with nano-sized cross-sections. [1b,4c, 5] Nanoelectrodes with conical shafts [6] are more robust but cannot be inserted deep inside cells without damaging the cytoplasmic membrane and the intracellular regions crossed over by the electrode tip.N anoelectrodes with near-cylindrical shafts produce minimal perturbations and reseal the cell membrane around the shaft to maintain the cell homeostasis during measurements. [4c] Many attempts aimed to circumvent this critical issue rely on electroactive materials confined in nano-etched cavities at the tip of glass nanocapillaries, [4c] etched carbon wires [3, 4d] or nanotubes (NTs), [7] nanowires (NWs) of noble metals [8] or tungsten [9] as well as core-shell NTs. [10] However, such NWs or NTs usually lack sufficient mechanical robustness to allow the routine fabrication of electrodes apt to be inserted into cells.Producing single NW/NTelectrodes (NWEs/NTEs) with high electrochemical and mechanical performances for intracellular detection with minimal damage...