Design of a novel aptamer/molecularly imprinted polymer hybrid modified Ag-Au@Insulin nanoclusters/Au-gate-based MoS2 nanosheet field-effect transistor for attomolar detection of BRCA1 gene.

Early detection of breast cancer, the first main cause of death in women, with robust assay platforms using appropriate biomarkers is of great importance for diagnosis and follow-up of the disease progression. This paper introduces an extra selective and sensitive label-free aptasensor for the screening of BRCA1 gene biomarker by taking advantage of a gate modified with aptamer and molecularly imprinted polymer hybrid (MIP) as a new synthetic receptor film coupled with an electrolyte-gated molybdenum disulfide (MoS2) field-effect transistor (FET). The Au gate surface of FET was modified with insulin stabilized bimetallic Ag-Au@nanoclusters (Ag-Au@InsNCs), after which, the immobilization of the hybridized aptamer and o-phenylenediamine was electropolymerized to form an aptamer-MIP hybrid receptor. The output characteristics of Apta-MIP hybrid modified Au gate MoS2 FET device were followed as a result of change in electrical double layer capacitance of electrolye-gate interface. The magnitude of decrease in the drain current showed a linear response over a wide concentration range of 10 aM to 1 nM of BRCA1 ssDNA with a sensitivity as high as 0.4851 µA/decade of concentration and a limit of detection (LOD) of 3.0 aM while very low responses observed for non-imprinted polymer. The devised aptasensor not only was capable to the discrimination of the complementary versus one-base mismatch BRCA1 ssDNA sequence, but also it could detect the complementary BRCA1 ssDNA in spiked human serum samples over a wide concentration range of 10 aM to 1.0 nM with a low LOD of 6.4 aM and a high sensitivity 0.3718 µA/decade.

How electrons Coulomb repulsion changes graphene band structure.

Base on effective medium theory we introduce a multi sites method for calculation of realistic energy bands of strongly correlated systems. We found due to approximated self energy, the density of states that obtained directly by calculated local Green function does not reflects system energy bands truly. By using this method we investigated how electrons repulsion renormalizes graphene bands. Graphene realistic bands calculated in both the dynamical mean field theory (DMFT) and four sites beyond super cell approximation for different repulsions. Our calculated interacting graphene bands illustrate a semi metal to a Mott insulator anti ferromagnetic phase transition at repulsions [Formula: see text] and [Formula: see text] for DMFT and four sites beyond super cell approximation respectively. These values are much less than finite size quantum Monte Carlo calculation prediction. We showed that the graphene bands are very sensitive to electrons repulsions and this phase transition happens at low repulsions in comparison to graphene band width.

A pH-responsive citric-acid/α-cyclodextrin-functionalized Fe3O4 nanoparticles as a nanocarrier for quercetin: An experimental and DFT study.

Developing new nanocarriers and understanding the interactions between the drug and host molecules in the nanocarrier at the molecular level is of importance for future of nanomedicine. In this work, we synthesized and characterized a series of iron oxide nanoparticles (IONPs) functionalized with different organic molecules (citric acid, α-cyclodextrin, and citric acid/α-cyclodextrin composite). It was found that incorporation of citric acid into the α-cyclodextrin had negligible effect on the adsorption efficiency (<5%) of citric acid/α-cyclodextrin functionalized IONPs, while the isotherm adsorption data were well described by the Langmuir isotherm model (qmax = 2.92 mg/g at T = 25 °C and pH = 7). In addition, the developed nanocarrier showed pH-responsive behavior for releasing the quercetin molecules as drug model, where the Korsmeyer-Peppas model could describe the release profile with Fickian diffusion (n < 0.45 for at all pH and temperatures). Then, Density functional theory was applied to calculate the absolute binding energies (ΔEb) of the complexation of quercetin with different host molecules in the developed nanocarriers. The calculated energies are as follow: 1) quercetin and citric acid: ΔEb = -16.58 kcal/mol, 2) quercetin and α-cyclodextrin: ΔEb = -46.98 kcal/mol, and 3) quercetin and citric acid/α-cyclodextrin composite: ΔEb = -40.15 kcal/mol. It was found that quercetin tends to interact with all hosts via formation of hydrogen bonds and van der Waals interactions. Finally, the cytotoxicity of the as-developed nanocarriers was evaluated using MTT assay and both normal NIH-3T3 and cancereous HeLa cells. The cell viability results showed that the quercetin could be delivered effectively to the HeLa cells due to the acidic environment inside the cells with minimum effect on the viability of NIH-3T3 cells. These results might open a new window to design of stimuli-responsive nanocarriers for drug delivery applications.

Low dimensions electron localization in the beyond real space super cell approximation.

Metal to insulator phase transition due to electron localization in disordered alloys (Anderson transition) and interacting electrons (Mott transition) systems is one of major problem in these fields. Multi site electron scattering is responsible for localization which can't be seen by single site approximations such as coherent potential approximation (CPA) and dynamical mean field theory (DMFT). Here we develop a multi site technique to calculate multi site electron scattering for observation of phenomenons such as electron localization especially in low dimension systems. Our self-energy in first Brillouin zone (FBZ) is casual, in contrast to previous approximation fully crystal electron wave vector, q, dependent and continuous with respect to q. It recovers coherent potential approximation in the single site approximation and is exact when the number of sites in the super cell approaches to the total number of lattice sites. We illustrate that this approximation undertakes electrons localization for one and two dimensional alloy systems which isn't observed by previous multi site approximations such as dynamical cluster approximation (DCA).

Superconducting Phases in Lithium Decorated Graphene LiC6.

A study of possible superconducting phases of graphene has been constructed in detail. A realistic tight binding model, fit to ab initio calculations, accounts for the Li-decoration of graphene with broken lattice symmetry, and includes s and d symmetry Bloch character that influences the gap symmetries that can arise. The resulting seven hybridized Li-C orbitals that support nine possible bond pairing amplitudes. The gap equation is solved for all possible gap symmetries. One band is weakly dispersive near the Fermi energy along Γ â†’ M where its Bloch wave function has linear combination of [Formula: see text] and dxy character, and is responsible for [Formula: see text] and dxy pairing with lowest pairing energy in our model. These symmetries almost preserve properties from a two band model of pristine graphene. Another part of this band, along K → Γ, is nearly degenerate with upper s band that favors extended s wave pairing which is not found in two band model. Upon electron doping to a critical chemical potential µ1 = 0.22 eV the pairing potential decreases, then increases until a second critical value µ2 = 1.3 eV at which a phase transition to a distorted s-wave occurs. The distortion of d- or s-wave phases are a consequence of decoration which is not appear in two band pristine model. In the pristine graphene these phases convert to usual d-wave or extended s-wave pairing.

Cobalt oxide nanoparticles as a novel high-efficiency fiber coating for solid phase microextraction of benzene, toluene, ethylbenzene and xylene from aqueous solutions.

In this work cobalt oxide nanoparticles were introduced for preparation of a novel solid phase microextraction (SPME) fiber coating. Chemical bath deposition (CBD) technique was used in order for synthesis and immobilization of the Co3O4 nanomaterials on a Pt wire for fabrication of SPME fiber. The prepared cobalt oxide coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The fiber was evaluated for the extraction of benzene, toluene, ethylbenzene and xylene (BTEX) in combination with GC-MS. A simplex optimization method was used to optimize the factors affecting the extraction efficiency. Under optimized conditions, the proposed fiber showed extraction efficiencies comparable to those of a commercial polydimethylsiloxane (PDMS) fiber toward the BTEX compounds. The repeatability of the fiber and its reproducibility, expressed as relative standard deviation (RSD), were lower than about 11%. No significant change was observed in the extraction efficiency of the new SPME fiber after over 50 extractions. The fiber was successfully applied to the determination of BTEX compounds in real samples. The proposed nanostructure cobalt oxide fiber is a promising alternative to the commercial fibers as it is robust, inexpensive and easily prepared.

Binding studies of pyriproxyfen to DNA by multispectroscopic atomic force microscopy and molecular modeling methods.

In this work, multispectroscopic atomic force microscopy and molecular modeling [ONIOM 2(B3LYP/6-31++G(d,p): Universal Force Field (UFF)) level] techniques were used to study the interaction between Calf-Thymus-DNA (CT-DNA) and pyriproxyfen (PYR) insecticide. The binding constant of PYR with double-strand deoxyribonucleic acid (ds-DNA) was obtained by ultraviolet-visible absorbance spectroscopy as 2.8×10(4) at 20°C. Thermodynamic parameters, that is, ΔH, ΔS°, and ΔG, were -53.82 kJ mol(-1), 96.11 J mol(-1), and -82.46 KJ mol(-1), respectively. Thermal denaturation study of DNA with PYR revealed the ΔT(m) of 3.0 and 6.0°C at r(i)=0.5 and 1.0, respectively. The Fourier transform infrared study showed a major interaction of PYR with G-C and A-T base pairs and a minor perturbation of the backbone PO(2) group. Further, PYR induces detectable changes in the circular dichroism spectrum of CT-DNA. In fluorimetric studies, the dynamic enhancement constants (k(D)) and bimolecular enhancement constant (k(B)) were calculated, which showed that the fluorescence enhancement was initiated by a static process in the ground state. The hybrid of quantum mechanical/molecular mechanics theoretical calculations revealed that the interaction is base sequence dependent, and PYR interacts more with DNA via the AT base sequence. From the data we concluded that PYR may interact with ds-DNA via two modes: intercalating and outside groove binding.

Ab initio density functional theory investigation of crystalline bundles of polygonized single-walled silicon carbide nanotubes.

By using ab initio density functional theory, the structural characterizations and electronic properties of two large-diameter (13, 13) and (14, 14) armchair silicon carbide nanotube (SiCNT) bundles are investigated. Full structural optimizations show that the cross sections of these large-diameter SiCNTs in the bundles have a nearly hexagonal shape. The effects of inter-tube coupling on the electronic dispersions of large-diameter SiCNT bundles are demonstrated. By comparing the band structures of the triangular lattices of (14, 14) SiCNTs with nearly hexagonal and circular cross sections we found that the polygonization of the tubes in the bundle leads to a further dispersion of the occupied bands and an increase in the bandgap by 0.18 eV.

When double-wall carbon nanotubes can become metallic or semiconducting.

The electronic properties of double-wall carbon nanotubes (DWCNTs) are investigated via density functional theory. The DWCNTs are separated into four categories wherein the inner-outer nanotubes are metal-metal, metal-semiconductor, semiconductor-metal and semiconductor-semiconductor single-wall nanotubes. The band structure of the DWCNTs, the local density of states of the inner and outer nanotubes, and the total density of states are calculated. We found that for the metal-metal DWCNTs, the inner and outer nanotubes remain metallic for different distances between the walls, while for the metal-semiconductor DWCNTs, decreasing the distance between the walls leads to a phase transition in which both nanotubes become metallic. In the case of semiconductor-metal DWCNTs, it is found that at some distance the inner wall becomes metallic, while the outer wall becomes a semiconductor, and if the distance is decreased, both walls become metallic. Finally, in the semiconductor-semiconductor DWCNTs, if the two walls are far from each other, then the whole DWCNT and both walls remain semiconducting. By decreasing the wall distance, first the inner, and then the outer, nanotube becomes metallic.

Impurity bound states in disordered d-wave superconductors.

Recent STM experiments on Bi2Sr2Ca2Cu3O10 observed sharp bound states associated with Zn and Ni impurities, as previously predicted theoretically. Here we extend the theory to the case of a finite concentration of impurities. Using the nonlocal coherent potential approximation, we show that the resonance peak both broadens and shifts as a function of impurity concentration.