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A modified signal probe containing a methylene blue label and a sticky end is used in a sandwich assay. A DNA target has hybridized the signal probe, the stick end has remained free to hybridize another target leading to the creation of a supersandwich structure containing multiple labels, which has led to large signal amplification upon monitoring by voltammetry.

An 'OR'gate is built by using label-free, dual-analyte electrochemical sensors and the activation of the logic gate through changing concentrations of cocaine and the relevant cDNA as inputs.

A nuclease-amplified DNA detection scheme is demonstrated in which exonuclease III is used to recycle target molecules, thus leading to enhanced sensitivity relative to traditional molecular beacons without any major restriction in the choice of target sequences. The exonuclease-amplified assay has detected target DNA at concentrations as low as 10 pM, which has represented a significant improvement over the equivalent molecular beacon alone.

The stronger binding of water-soluble, cationic conjugated polymer to single-stranded DNA with higher affinity has resulted from the greater hydrophobicity of single-stranded DNA. The different affinities between the cationic conjugated polymer and various forms of DNA are used for designing a variety of biosensors.

The grafted polymer from silicon nanowire arrays via surface-initiated atom transfer radical polymerization was used to construct nanoscale topography on a thermally responsive poly(N-isopropylacrylamide) (PNIPAAm) surface. The results provide insight into the applications of PNIPAAm in the fields of biomaterials and biomedicine under human physiological temperature and as a new strategy for fabricating other blood-compatible materials.

A novel biomimetic nanochannel system is described having an ion concentration effect that has provided a nonlinear response to potassium ion at the concentration ranging from 0 to 1500 [micro]m. The G-quadruplex DNA is immobilized onto a synthetic nanopore that has undergone a potassium-responsive conformational change and has induced the change in the effective pore size

The development of a new nanopore-DNA system for the gating of the single synthetic solid-state conical nanopores by the proton-driven DNA molecular motors is explained. The gating efficiency of the system is shown to be maximum, when the length of the attached DNA molecule is same as the tip diameter of the nanopore well.

Managinginterfacial instability is crucial for enhancing cyclabilityin lithium-ion batteries (LIBs), yet little attention has been devotedto this issue until recently. Here, we introduce graphene as an interfaciallayer between the current collector and the anode composed of Si nanowires(SiNWs) to improve the cycling capability of LIBs. The atomicallythin graphene lessened the stress accumulated by volumetric mismatchand inhibited interfacial reactions that would accelerate the fatigueof Si anodes. By simply incorporating graphene at the interface, wedemonstrated significantly enhanced cycling stability for SiNW-basedLIB anodes, with retentions of more than 2400 mAh/g specific chargecapacity over 200 cycles, 2.7 times that of SiNWs on a bare currentcollector. [ABSTRACT FROM AUTHOR]

A cooperative dual-responsive polypeptide surface switching between superhydrophilic and superhydrophobic states is presented. This macroscopic phenomenon of surface originates from the combination of the cooperative unfolding/aggregation of the poly-l-lysine (PLL) immobilized on the substrate with micro/nanocomposite structure in response to pH and temperature. At pH lower than the pKaof PLL (∼11.0), PLL mainly adopts a random coil conformation, which corresponds to the superhydrophilic state on the rough surface substrate. Raising the pH to higher than the pKaallows the appearance of α-helix conformation, which also corresponds to the hydrophilic state. However, heating up the surface at pH higher than the pKadestabilizes the α-helix conformation and induces the formation of aggregated β-sheet structures, which represents the superhydrophobic state. Lowering the pH and temperature simultaneously switches a reversible conversion from superhydrophobic to superhydrophilic states. In the switching process, the hydrophobicity and hydrophilicity can be “memorized” due to the cooperative pH and temperature stimuli-induced unfolding/aggregation behaviors of PLL. This provides a new exciting prospect for understanding surface properties of polypeptides and the design of smart material surfaces with potential applications in nanodevices, bioseparation, and biosensors. [ABSTRACT FROM AUTHOR]

Pd-catalyzed alkoxycarbonylation of alkynes provided a redox-neutral method to selectively access branched/linear α,β-unsaturated monoesters and 1,4-dicarboxylic acid diesters. Herein, a systematic computational study was performed to elucidate the mechanism and origin of ligand-controlled chemo- and regioselectivities. It is found that the catalytic cycle, including hydrometallation, carbon monoxide insertion, and methanolysis, is more likely than that involving palladium alkoxycarbonyl intermediates. Both hydrometallation and methanolysis stages are important to determine the chemo- and regioselectivities. Hydrometallation proceeds via anti-Markovnikov-selective migratory insertion or Markovnikov-selective ligand-participated electrophilic addition. A flexible bidentate phosphine ligand slows down migratory insertion due to the stronger trans effect of the CO ligand but accelerates the ligand-participated electrophilic addition by adopting better orbital orientations. On the other hand, a ligand-participated mechanism and an unrevealed mechanism involving ketene intermediates can promote methanolysis, whereas ligands with large bite angles or bulky substituents are detrimental to methanolysis. On the basis of these mechanistic foundations, the influence of the flexibility, basicity, bite angle, and steric hindrance of ligands on chemo- and regioselectivities was clarified. The present study provided more universal and deeper mechanistic insights into Pd-catalyzed alkoxycarbonylation reactions and shed light on the superior regulation performance of the bifunctional pyridyl-containing phosphine ligands.

Heparin (Hep), widely used in clinics as an anticoagulant drug, has high degrees of heterogeneity and shares a similar disaccharide repeating unit with its GAG analogues. The development of reliable and convenient methods to discriminate Hep from its GAG analogues and detect trace GAG contaminants in Hep is meaningful for safe usage of Hep in clinics. Herein, five porphyrin-GO nanocomposites denoted as PP1-GO , PP2a-GO , PP2b-GO , PP3-GO , and PP4-GO were synthesized by assembling corresponding positively charged porphyrins onto the surface of GO. Controlled by a different number and position of the 4- N -methyl-pyridyl groups substituted at the porphyrins, these nanocomposites were determined to be cross-reactive toward Hep and other three commonly used GAGs including Chs, HA, and DS. A NIR sensor array PP-GO was thus constructed using these nanocomposites for GAGs discrimination and Hep quality control through pattern-based recognition. HCA and LDA calculated results indicated that PP-GO was powerful for discrimination of Hep and its GAG analogues in both PBS and even 10% serum media. Moreover, the PP-GO sensor array was successfully applied for the reliable discrimination of trace GAG contaminants in Hep with 100% accuracy.

Photoresponsive nanochannel systems whose ionic transportation properties can be controlled by the photoelectric effect, such as for green chlorophyll pigments in plants, are attracting widespread attention. Herein, we prepared photoresponsive heterogeneous nanochannels by decorating self-assembled tetra(4-sulfonatophenyl)porphyrin (TPPS) nanofiber membranes on a membrane of hourglass-shaped alumina (Al 2 O 3 ) nanochannels using the diffusion-limited patterning (DLP) method. The close arrangement of large-area nanofibers promoted the photoresponse sensitivity of the heterogeneous nanochannels, which showed the highest ionic transportation current. With illumination comparable to sunlight in intensity, the photoresponsive ionic current was approximately 9.7 μA, demonstrating photoswitching, which could be used to regulate the reversible transformation of ionic currents. Meanwhile, the cooperative effect of the TPPS nanofibers assembled at the entrance to the nanochannels and the TPPS molecules inside the nanochannels allowed the heterogeneous nanochannels to exhibit a good rectifying performance.

In this work, the synthetic alumina nanochannels with bi-, tri-, and tetra-branched geometry structures exhibited ionic current rectifications with nonlinear I-V curves. Such diode performance of the branched alumina nanochannel is mainly dependent on the cooperative asymmetry of the branched structure and the surface-charge distribution on inner walls. By regulating the geometry, electrolyte pH, and solution concentration, the tunable ionic rectification properties are effectively obtained including both the rectification ratios and the rectifying direction that were deduced from the converted ion selectivity. This nanofluidic diode may open up a new opportunity for the application of the complex nanofluidic devices in contrast to previously reported channels to provide molecular analysis, controlled mass transport, drug release, and various logic gate operations.