Patterned Paper Sensors Printed with Long‐Chain DNA Aptamers

There is growing interest in developing printable paper sensors to enable rapid testing of analytes for environmental, food safety, and clinical applications. A major challenge is to find suitable bioinks that are amenable to high‐speed printing and remain functional after printing. We report on a simple and effective approach wherein an aqueous ink composed of megadalton‐sized tandem repeating structure‐switching DNA aptamers (concatemeric aptamers) is used to rapidly create patterned paper sensors on filter paper by inkjet printing. These concatemeric aptamer reporters remain immobilized at the point of printing through strong adsorption but retain sufficient segmental mobility to undergo structure switching and fluorescence signaling to provide both qualitative and quantitative detection of small molecules and protein targets. The convenience of inkjet printing allows for the patterning of internally referenced sensors with multiplexed detection, and provides a generic platform for on‐demand printing of sensors even in remote locations.     

Amperometric Ethanol Biosensor Based on Carbon Nanotubes Dispersed in Sol–Gel‐Derived Titania–Nafion Composite Film

Composite solution of sol–gel‐derived titania and perfluorosulfonated ionomer (Nafion) was used as a solubilizing agent for multiwalled carbon nanotubes (CNT) as well as an encapsulation matrix for alcohol dehydrogenase (ADH) for the fabrication of a highly sensitive and stable amperometric ethanol biosensor. ADH was immobilized within a thin film of CNT–titania–Nafion composite film coated on a glassy carbon electrode. Because of the mesoporous nature of the CNT–titania–Nafion composite film, the present biosensor exhibited remarkably fast response time within 2 s. The presence of CNT in the composite film increases not only the sensitivity of the ethanol biosensor but also the long‐term stability of the biosensor. The present biosensor responds linearly to ethanol in the wide concentration ranges from 1.0×10^?5 M to 3.0×10^?3 M with the sensitivity of 51.6 mA M^?1cm^?2. The present biosensor showed good long‐term stability with 75% of its activity retained after 4 weeks of storage in 50 mM phosphate buffer at pH 7.0.     

Ideal‐Filter Capillary Electrophoresis (IFCE) Facilitates the One‐Step Selection of Aptamers

Selection of aptamers from oligonucleotide libraries currently requires multiple rounds of alternating steps of partitioning of binders from nonbinders and enzymatic amplification of all collected oligonucleotides. Herein, we report a highly practical solution for reliable one‐step selection of aptamers. We introduce partitioning by ideal‐filter capillary electrophoresis (IFCE) in which binders and nonbinders move in the opposite directions. The efficiency of IFCE‐based partitioning reaches 10⁹, which is ten million times higher than that of typical solid‐phase partitioning methods. One step of IFCE‐based partitioning is sufficient for the selection of a high‐affinity aptamer pool for a protein target. Partitioning by IFCE promises to become an indispensable tool for fast and robust selection of binders from different types of oligonucleotide libraries.     

Sol‐Gel‐Process in the Ammono‐System – a Novel Access to Silicon Based Nitrides

Controlled coammonolysis of elementalkylamides in aprotic organic solvents at low temperatures have been shown to result in the formation of polyazanes. The synthetic procedure developed may be addressed as “sol‐gel‐route in the ammono system”. Pyrolysis of these novel polymer precursors gave access to multinary nitrides. For the model systems Si(NHMe)₄/B(NMe₂)₃, Si(NHMe)₄/Ti(NMe₂)₄, and Si(NHMe)₄/Ta(NMe₂)₅ polymeric boro‐, titano and tantalosilazanes were obtained. Pyrolysis in ammonia at 1000 °C yielded amorphous silicon boron nitride, silicon titanium nitride and silicon tantalum nitride powders; further heating of the nitride powders at 1500 °C in nitrogen atmosphere led to the formation of partly crystalline composites of α‐Si₃N₄ and amorphous silicon boron nitride for the Si/B/N system, a composite of finely dispersed TiN and amorphous silicon titanium nitride for the Si/Ti/N system, and crystalline TaN and amorphous silicon nitride for the Si/Ta/N system. Furthermore, the structure and pyrolysis chemistry of the polymeric intermediates, as well as the morphology of the pyrolysis products, were studied by NMR, MAS‐NMR, FT‐IR, DTA‐TG‐MS, XRD, SEM, EDX and elemental analyses.     

Fuel‐Responsive Allosteric DNA‐Based Aptamers for the Transient Release of ATP and Cocaine

We show herein that allostery offers a key strategy for the design of out‐of‐equilibrium systems by engineering allosteric DNA‐based nanodevices for the transient loading and release of small organic molecules. To demonstrate the generality of our approach, we used two model DNA‐based aptamers that bind ATP and cocaine through a target‐induced conformational change. We re‐engineered these aptamers so that their affinity towards their specific target is controlled by a DNA sequence acting as an allosteric inhibitor. The use of an enzyme that specifically cleaves the inhibitor only when it is bound to the aptamer generates a transient allosteric control that leads to the release of ATP or cocaine from the aptamers. Our approach confirms that the programmability and predictability of nucleic acids make synthetic DNA/RNA the perfect candidate material to re‐engineer synthetic receptors that can undergo chemical fuel‐triggered release of small‐molecule cargoes and to rationally design non‐equilibrium systems.     

Copper Oxide Nanoparticle Modified Sol–Gel‐Derived Carbon Ceramic by Microwave Irradiation,and Its Application for Determination of Adenine at Very Low Potential

In this work the copper oxide nanoparticles simultaneous with sol–gel‐derived carbon ceramic production were synthesized and doped in ceramic by microwave irradiation in a few minutes without using any catalyst and organic solvent. The ceramic composition was characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and Fourier transforms infrared (FT‐IR), and its surface morphology was investigated by scanning electron microscopy (SEM). The proposed ceramic with detection limit of 0.1 µM, was used for electrocatalytic determination of adenine at potential about 700 mV lower than its usual oxidation potential.