Detection of analytes by means of field-effect transistors bearing ligand-specific receptors is fundamentally limited by the shielding created by the electrical double layer (the "Debye length" limitation). We detected small molecules under physiological high-ionic strength conditions by modifying printed ultrathin metal-oxide field-effect transistor arrays with deoxyribonucleotide aptamers selected to bind their targets adaptively. Target-induced conformational changes of negatively charged aptamer phosphodiester backbones in close proximity to semiconductor channels gated conductance in physiological buffers, resulting in highly sensitive detection. Sensing of charged and electroneutral targets (serotonin, dopamine, glucose, and sphingosine-1-phosphate) was enabled by specifically isolated aptameric stem-loop receptors.

In the last five years and currently, research on solar fuels has been intense and no sub-area in this field has been more active than the development of water oxidation catalysts (WOCs). In this timeframe, a new class of molecular water oxidation catalysts based on polyoxometalates have been reported that combine the advantages of homogeneous and heterogeneous catalysts. This review addresses central issues in green energy generation, the challenges in water oxidation catalyst development, and the possible uses of polyoxometalates in green energy science.

We demonstrate straightforward fabrication of highly sensitive biosensor arrays based on field-effect transistors, using an efficient high-throughput, large-area patterning process. Chemical lift-off lithography is used to construct field-effect transistor arrays with high spatial precision suitable for the fabrication of both micrometer- and nanometer-scale devices. Sol-gel processing is used to deposit ultrathin (∼4 nm) In2O3 films as semiconducting channel layers. The aqueous sol-gel process produces uniform In2O3 coatings with thicknesses of a few nanometers over large areas through simple spin-coating, and only low-temperature thermal annealing of the coatings is required. The ultrathin In2O3 enables construction of highly sensitive and selective biosensors through immobilization of specific aptamers to the channel surface; the ability to detect subnanomolar concentrations of dopamine is demonstrated.

Wearable technologies for personalized monitoring require sensors that track biomarkers often present at low levels. Cortisol-a key stress biomarker-is present in sweat at low nanomolar concentrations. Previous wearable sensing systems are limited to analytes in the micromolar-millimolar ranges. To overcome this and other limitations, we developed a flexible field-effect transistor (FET) biosensor array that exploits a previously unreported cortisol aptamer coupled to nanometer-thin-film In 2 O 3 FETs. Cortisol levels were determined via molecular recognition by aptamers where binding was transduced to electrical signals on FETs. The physiological relevance of cortisol as a stress biomarker was demonstrated by tracking salivary cortisol levels in participants in a Trier Social Stress Test and establishing correlations between cortisol in diurnal saliva and sweat samples. These correlations motivated the development and on-body validation of an aptamer-FET array-based smartwatch equipped with a custom, multichannel, self-referencing, and autonomous source measurement unit enabling seamless, real-time cortisol sweat sensing.

An efficient nonviral platform for high-throughput and subcellular precision targeted intracellular delivery of nucleic acids in cell culture based on magnetic nanospears is reported. These magnetic nanospears are made of Au/Ni/Si (∼5 μm in length with tip diameters <50 nm) and fabricated by nanosphere lithography and metal deposition. A magnet is used to direct the mechanical motion of a single nanospear, enabling precise control of position and three-dimensional rotation. These nanospears were further functionalized with enhanced green fluorescent protein (eGFP)-expression plasmids via a layer-by-layer approach before release from the underlying silicon substrate. Plasmid functionalized nanospears are guided magnetically to approach target adherent U87 glioblastoma cells, penetrating the cell membrane to enable intracellular delivery of the plasmid cargo. After 24 h, the target cell expresses green fluorescence indicating successful transfection. This nanospear-mediated transfection is readily scalable for the simultaneous manipulation of multiple cells using a rotating magnet. Cell viability >90% and transfection rates >80% were achieved, which exceed conventional nonviral intracellular methods. This approach is compatible with good manufacturing practices, circumventing barriers to the translation and clinical deployment of emerging cellular therapies.

A new pentanickel silicotungstate complex, K(10)H(2)[Ni(5)(OH)(6)(OH(2))(3)(Si(2)W(18)O(66))]·34H(2)O (KH-), has been synthesized and characterized by X-ray crystallography and several other methods. Dynamic light scattering, kinetics and other experiments confirm that in the presence of [Ru(bpy)(3)](2+) (the photosensitizer for light-driven water oxidations) and [Ru(bpy)(3)](3+) (the oxidant in the dark water oxidations) exists in an equilibrium between solution (soluble) and a [Ru(bpy)(3)](n+)- complex (minimally soluble) form. This new pentanickel polyoxometalate catalyzes efficient water oxidation in both the dark and on irradiation with 455 nm LED light with 1.0 mM [Ru(bpy)(3)](2+) photosensitizer and 5.0 mM Na(2)S(2)O(8), sacrificial electron acceptor. Four lines of evidence indicate that in this solution [symbol:see text] Ru(bpy)(3)](n+)- complex equilibrium remains molecular and does not decompose to nickel hydroxide particles.

Implantable aptamer transistor probes for in vivo neurotransmitter monitoring advance brain activity recording.

Summary Flexible sensors are essential for advancing implantable and wearable bioelectronics toward monitoring chemical signals within and on the body. Developing biosensors for monitoring multiple neurotransmitters in real time represents a key in vivo application that will increase understanding of information encoded in brain neurochemical fluxes. Here, arrays of devices having multiple In 2 O 3 nanoribbon field-effect transistors (FETs) were fabricated on 1.4-μm-thick polyethylene terephthalate (PET) substrates using shadow mask patterning techniques. Thin PET-FET devices withstood crumpling and bending such that stable transistor performance with high mobility was maintained over >100 bending cycles. Real-time detection of the small-molecule neurotransmitters serotonin and dopamine was achieved by immobilizing recently identified high-affinity nucleic-acid aptamers on individual In 2 O 3 nanoribbon devices. Limits of detection were 10 fM for serotonin and dopamine with detection ranges spanning eight orders of magnitude. Simultaneous sensing of temperature, pH, serotonin, and dopamine enabled integration of physiological and neurochemical data from individual bioelectronic devices.