Electrochemical biosensors for monitoring the recognition of glycoprotein-lectin interactions

Despite the wide applicability and specificity of lectins to carbohydrate moieties, there are few lectin specific biosensors. This is attributed to the difficulty in defining the relevant experimental parameters to measure for sensing. We hereby describe the development of direct and indirect electrochemical sensors to determine the exact trace amounts of probarley lectin (ProBL) and its conversion product wheat germ agglutinin (WGA). In addition to WGA, the antigens (ProBL) employed in this study were over expressed in bacteria, isolated from protein bodies, and purified using immobilized N-acetylglusamine in order to obtain correctly folded active lectins. The amperometric immunosensor uses cell lines producing monoclonal antibody (mAB) to the pro-region of ProBL over expressed from Escherichia coli. The efficacy and sensing characteristics of the lectin were optimized using monoclonal antibody to WGA and the resulting sensor was found to detect only ProBL in the linear range 10⁻³-10² μg mL⁻¹ and a detection limit of 10⁻³ μg mL⁻¹.     

One-pot green synthesis and cytotoxicity of new <Emphasis Type="Italic">α</Emphasis>-aminophosphonates

A novel series of α-aminophosphonates containing the trifluoromethyl aniline moiety were obtained in high yields by condensation of 2-methyl-3-trifluoromethyl aniline, aryl/heteroaryl aldehydes and dimethylphosphite in the presence of chitosan as a catalyst. The molecular modeling studies revealed their important structural features of binding affinities towards the target enzyme. The cytotoxicity of these compounds was evaluated against PC-3(prostate cancer), MCF-7 (breast cancer), HeLa(cCervix Cancer), U973, K562 and HL60 human lLeukemia cell lines. Compound 4k with a pyrene moiety showed high potency against a breast cancer cell line, while compounds 4g and 4k exhibited more promising cytotoxicity against U973, K562 and HL60 cell lines.     

All-optical flip-flop based on vertical cavity semiconductor optical amplifiers

We report the operation of an all-optical set-reset (SR) flip-flop based on vertical cavity semiconductor optical amplifiers (VCSOAs). This flip-flop is cascadable, has low optical switching power (~10 microW), and has the potential to be integrated on a small footprint (~100 microm(2)). The flip-flop is composed of two cross-coupled electrically pumped VCSOA inverters and uses the principles of cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics to achieve flip-flop functionality. We believe that, when integrated on chip, this type of all-optical flip-flop opens new prospects for implementing all-optical fast memories and timing regeneration circuits.     

Green synthesis of diethyl((2-iodo-4-(trifluoromethyl)phenyl)amino)(aryl)methyl)phosphonates as potent α-glucosidase inhibitors

Abstract

Novel diethyl((2-iodo-4-(trifluoromethyl)phenyl)amino)(aryl)methyl)phosphonates (4a-j) were synthesized via a simple and efficient one pot by three-component condensation reaction (Kabachnik-Fields reaction) of 2-iodo-4-trifluoromethyl aniline, aromatic aldehydes and diethyl phosphite in presence of anatase TiO₂ nanoparticles as catalyst under solvent free conditions. The molecular docking studies of synthesized compounds with α-glucosidase enzyme revealed that these compounds have strong α-glucosidase inhibitory activity. The synthesized compounds (4a-j) are also screened for in vitro α-glucosidase inhibitory activity and the results showed compound 4i as the strongest inhibitor and compounds 4a, 4b, 4f and 4g as stronger inhibitors even better than the reference standard acarbose.     

Size tunable three-dimensional annular laser trap based on axicons

A three-dimensional (3D) ring-shaped laser trap has been built using axicons. The diameter of this laser trap ranges from 70 to 140 mum and is adjusted by simply changing the position of one axicon in the optical path. Parallel 3D trapping of 5 mum silica microspheres and 3D confinement of cells along the ring are demonstrated. In this system the special optical properties of axicons are used to create a continuous annular trap with high power efficiency and a constant numerical aperture. This new approach, without any mechanical scanning, offers significant potential for applications in cell motility analysis and biotropism studies.     

Alternating current electrokinetic separation and detection of DNA nanoparticles in high-conductance solutions

In biomedical research and diagnostics, it is a significant challenge to directly isolate and identify rare cells and potential biomarkers in blood, plasma and other clinical samples. Additionally, the advent of bionanotechnology is leading to numerous drug delivery approaches that involve encapsulation of drugs and imaging agents within nanoparticles, which now will also have to be identified and separated from blood and plasma. Alternating current (AC) electrokinetic techniques such as dielectrophoresis (DEP) offer a particularly attractive mechanism for the separation of cells and nanoparticles. Unfortunately, present DEP techniques require the dilution of blood/plasma, thus making the technology less suitable for clinical sample preparation. Using array devices with microelectrodes over-coated with porous hydrogel layers, AC electric field conditions have been found which allow the separation of DNA nanoparticles to be achieved under high-conductance (ionic strength) conditions. At AC frequencies in the 3000 Hz to 10,000 Hz range and 10 volts peak-to-peak, the separation of 10-microm polystyrene particles into low field regions, and 60-nm DNA-derivatized nanoparticles and 200-nm nanoparticles into high-field regions was carried out in 149 mM 1xPBS buffer (1.68 S/m). These results may allow AC electrokinetic systems to be developed that can be used with clinically relevant samples under physiological conditions.     

Palladium acetate-catalysed one-pot green synthesis of bis α-aminophosphonates

Research on Chemical Intermediates - A simple and effective green method has been developed for the synthesis of a series of novel bis α-aminophosphonate derivatives (4a–j) by the...     

Canonical functions of admissible measures in the half-plane

For a γ-admissible measure λ in the upper half-plane, we introduce the notion of canonical function, generalizing the canonical Nevanlinna product for analytic functions of finite order in the half-plane. It is shown that, for any growth function γ defined by the Boutroux proximate order, the given definition and the canonical Nevanlinna product coincide.