A needle-like Cu2CdSnS4 alloy nanostructure-based integrated electrochemical biosensor for detecting the DNA of Dengue serotype 2

Microchimica Acta - The authors describe an integrated biosensor for amperometric DNA detection of Dengue virus in real time. Cu2CdSnS4 (CCTS) quaternary alloy nanostructures were successfully...     

220-fs erbium-ytterbium:glass laser mode locked by a broadband low-loss silicon/germanium saturable absorber

We demonstrate femtosecond performance of an ultrabroadband high-index-contrast saturable Bragg reflector consisting of a silicon/silicon dioxide/germanium structure that is fully compatible with CMOS processing. This device offers a reflectivity bandwidth of over 700 nm and subpicosecond recovery time of the saturable loss. It is used to achieve mode locking of an Er-Yb:glass laser centered at 1540 nm, generating 220-fs pulses, with what is to our knowledge the broadest output spectrum to date.     

Single Step Fabrication of Chitosan Nanocrystals Using <Emphasis Type="Italic">Penaeus semisulcatus</Emphasis>: Potential as New Insecticides,Antimicrobials and Plant Growth Promoters

In this study, chitosan nanoparticles (CH-NPs) were synthesized using Penaeus semisulcatus shrimp shells and characterized using UV–Vis and FT-IR spectroscopy, as well as XRD and HR-TEM analyses. CH-NPs were investigated for growth inhibition properties against selected species of bacterial and fungal pathogens, showing performances higher or comparable over positive controls, respectively. Furthermore, CH-NPs were tested on three important mosquito vectors, achieving LC₅₀ from 12.27 to 14.62 µg/ml. In addition, CH-NPs were evaluated using in vitro plant tissue culture by rooting gel method, to enhance the vegetative growth of the medicinal plant species Sphaeranthus indicus. With the simple technique presented here, large-scale industrial production of CH-NPs is possible. They can be used to develop pesticides highly effective against mosquito vectors of high medical and veterinary importance, as well as for plant tissue culture and food packaging applications.     

Evaluation of nucleic acid duplex formation on gold over layers in biosensor fabricated using Czochralski-grown single-crystal silicon substrate

With a view to developing an economical and elegant biosensor chip, we compared the efficiencies of biosensors that use gold-coated single-crystal silicon and amorphous glass substrates. The reflectivity of light over a wide range of wavelengths was higher from gold layer coated single-crystal silicon substrates than from glass substrates. Furthermore, the efficiency of reflection from gold layers of two different thicknesses was examined. The thicker gold layer (100 nm) on the single-crystal silicon showed a higher reflectivity than the thinner gold film (10 nm). The formation of a nucleic acid duplex and aptamer–ligand interactions were evaluated on these gold layers, and a crystalline silicon substrate coated with the 100-nm-thick gold layer is proposed as an alternative substrate for studies of interactions of biomolecules.     

A topology preserving method for generating equilibrated polymer melts in computer simulations

A new method for generating equilibrated configurations of polymer melts is presented. In this method, the molecular weight of an equilibrated melt of polymers is successively doubled by affinely scaling the simulation box and adding beads along the contour of the chains. At each stage of molecular weight doubling, compressive deformations are produced on all length scales, while the random walk nature of the polymers is preserved, thereby requiring relaxation times significantly smaller than the reptation time to fully equilibrate the melt. This method preserves the topological state of individual polymers in the melt and its effectiveness is demonstrated for linear polymers with molecular weight N up to 1024, and cyclic polymers with N up to 8192. For the range of N studied, the method requires simulation time that scales as N(2) and is thought to be applicable to a variety of polymer architectures.     

Improved in Vitro Permeation of Nabumetone across Rat Skin from 1‐O‐Alkylglycerol/Lecithin Stabilized o/w Nanoemulsions

In vitro permeation of nabumetone across rat skin from nanoemulsions of soybean oil in 2.5% aqueous glycerol stabilized with a blend of lecithin and 1‐O‐alkylglycerol (C₁₀, C₁₂, C₁₄, or C₁₆ chain length) was studied. The mean droplet size of the emulsions was in the range of 214 to 280 nm. 1‐O‐Alkylglycerol stabilized emulsions showed significant enhancement in permeation of nabumetone. This enhancement is attributed to the interaction of 1‐O‐alkylglycerol with the skin lipids, fluidizing the lipid matrix and bringing about disordering effect. The extent of interaction appears to depend on chain length of 1‐O‐alkylglycerol. 1‐O‐Decylglycerol stabilized emulsion showed highest flux in the first four hours and did not exhibit any lag time. The other emulsions showed increase in lag time with increase in the chain length of 1‐O‐alkylglycerol. Control nabumetone solution exhibited highest overall flux, but it showed lower flux than nanoemulsions stabilized by 1‐O‐decylglycerol for the initial four hours and a significantly higher flux thereafter. This appears to be due to slow extraction of skin lipid by the solvent action of control solution and consequent permeabilization of the skin.     

Surface functionalization chemistries on highly sensitive silica-based sensor chips

The surfaces of silica-based sensor chips, designed for evanescent-field-coupled waveguide-mode sensors, were functionalized using various surface chemistries. The immobilization of molecular entities on the functionalized silica surfaces was monitored using various microscopic techniques (scanning electron, fluorescence, and atomic force microscopies). Further, gold nanoparticle-based signal enhancement analyses were performed with protein conjugation on different functionalized surfaces using a waveguide-mode sensor. Based on these analyses, the sensor surfaces modified with glutaraldehyde (Glu) and carbonyldiimidazole were found to be good for molecules of different sizes. In addition, it can be inferred that the Glu-modified surface may be suitable for small molecules with diameters around 5 nm owing to its surface roughness. The modified surface with carbonyldiimidazole is suitable for the direct immobilization of larger molecules especially for biomolecular assemblies without intermediate chemical modifications.     

Single-stranded DNA (ssDNA) production in DNA aptamer generation

The discovery that synthetic short chain nucleic acids are capable of selective binding to biological targets has made them to be widely used as molecular recognition elements. These nucleic acids, called aptamers, are comprised of two types, DNA and RNA aptamers, where the DNA aptamer is preferred over the latter due to its stability, making it widely used in a number of applications. However, the success of the DNA selection process through Systematic Evolution of Ligands by Exponential Enrichment (SELEX) experiments is very much dependent on its most critical step, which is the conversion of the dsDNA to ssDNA. There is a plethora of methods available in generating ssDNA from the corresponding dsDNA. These include asymmetric PCR, biotin-streptavidin separation, lambda exonuclease digestion and size separation on denaturing-urea PAGE. Herein, different methods of ssDNA generation following the PCR amplification step in SELEX are reviewed.