Abstract: Mid-infrared spectra of biological matter such as tissues or microbial and eukaryotic cells measured in a transmission-type optical setup frequently show strongly distorted line shapes which arise from mixing of absorption and scattering contributions. Scattering-associated distorted line shapes may considerably complicate the analysis and interpretation of the infrared spectra and large efforts have been made to understand the mechanisms of scattering in biological matter and to compensate for spectral alterations caused by scattering. The goals of the present study were two-fold: firstly, to get a deeper understanding of the physics of scattering of biological systems and to explore how physical parameters of the scatterers such as shape, size and refractive index influence the line shape distortions observed. In this context, simulations based on the full Mie scattering formalism for spherical particles were found to be useful in explaining the characteristics of the Mie scatter-associated distortions and yielded a size criterion for the scattering particles similar to the well-known near field criterion. The second objective of the study was to investigate whether alternative optical setups allow minimisation of the effects of scattering. For this purpose, an optical system is proposed which is composed of an integrating sphere unit originally designed for diffuse reflection measurements, an off-axis DLaTGS detector to collect scattered and transmitted light components and a commercial Fourier transform infrared (FTIR) spectrometer. In the context of this study transmission type (tt-) FTIR spectra and spectra acquired by means of the integrating sphere setup (is-FTIR) were acquired from monodisperse poly(methyl) methacrylate (PMMA) microspheres of systematically varying sizes. The tt-FTIR spectral data of different PMMA particles confirmed earlier observations such as the presence of size-dependent oscillating spectral baselines, peak shifts, or derivative-like spectral line shapes. Such effects could be dramatically minimised when is-FTIR spectra were acquired by the integrating sphere unit. Utilisation of an integrating sphere is suggested as a convenient and easy-to use alternative to computer-based methods of scatter correction.

Abstract: This communication describes a simple and cost-effective method for fabricating glass microchannels by wet chemical etching using masks made by xurography in vinyl adhesive films. Analytical performance of microfluidic devices fabricated using the new approach was evaluated by microchip electrophoresis coupled to capacitively coupled contactless conductivity detection (C(4)D) and laser-induced fluorescence (LIF) detection.

Abstract: We demonstrate the first example of the fabrication of co-planar 50 μm (width) screen printed graphite microbands (length: 20 mm), fabricated entirely via screen printing which are characterised both microscopically and electrochemically via cyclic voltammetry and evaluated towards the sensing of NADH offering a competitive limit of detection (3σ) of 0.24 μM. The fabricated electrodes are also shown to be extended to gold screen printed microbands which are evaluated towards the sensing of chromium(VI) offering a limit of detection (3σ) of 2.65 μM. These microbands are seen to be the first produced entirely through screen printed technology potentially allowing disposable, mass produced microbands to be realised.

Abstract: For the determination of lenalidomide using carbamazepine as an internal standard, an ultra-fast stability indicating LC-MS/MS method was developed, validated and optimized to support clinical advancement. The samples were prepared by solid-phase extraction. The calibration range was 2-1000 ng mL(-1), for which a quadratic regression (1/x(2)) was best fitted. The method was validated and a 3(2) factorial was employed using Box-Behnken experimental design for the validation of robustness. These designs have three factors such as mobile phase composition (X(1)), flow rate (X(2)) and pH (X(3)) while peak area (Y(1)) and retention time (Y(2)) were taken as response. This showed that little changes in mobile phase and flow rate affect the response while pH has no affect. Lenalidomide and carbamazepine were stable in human plasma after five freeze thaw cycles, at room temperature for 23.7 h, bench top stability for 6.4 h. This method competes with all the regulatory requirements for selectivity, sensitivity, precision, accuracy, and stability for the determination of lenalidomide in human plasma, as well as being highly sensitive and effective for the pharmacokinetic and bioequivalence study of lenalidomide.

Abstract: We describe a sensitive electrochemical immunoassay for Salmonella enterica serovar Typhimurium, a common foodborne pathogen which can cause infection at extremely small doses. The assay is based on the recognition of DNA biobarcode labels by differential pulse anodic stripping voltammetry (DPASV), following Ag enhancement. The biobarcodes consist of latex spheres (mean diameter 506 nm ± 22 nm) modified by ferromagnetic Fe3O4 particles. Each biobarcode is loaded by adsorption with approx. 27 molecules of mouse monoclonal antibody against S. Typhimurium and 3.5 × 10(5) molecules of 12 mer ssDNA. The assay is performed by adding the biobarcode, S. Typhimurium cells, and biotin-conjugated rabbit polyclonal antibody against Salmonella into well plates. After antigen-antibody binding, magnetic collection enables the excess polyclonal antibody to be washed off. Exposure to avidin-coated screen printed electrodes, and formation of the avidin-biotin bond, then enables the excess biobarcode to be removed. The biobarcode remaining on the electrode is quantified by DPASV measurement of Ag(+) ions following catalytic Ag deposition. The assay showed a negligible response to 10(7) CFU mL(-1)E. coli and had a limit of detection of 12 CFU mL(-1) in buffer, and 13 to 26 CFU mL(-1) for heat-killed and whole cell S. Typhimurium in plain milk, green bean sprouts and raw eggs. To the best of our knowledge, this is the lowest reported limit of detection for Salmonella by an electrochemical immunoassay not requiring sample pre-enrichment.

Abstract: Unusual electropolymerization of aniline to polyaniline (PANI) in a neutral pH solution has been successfully demonstrated using a multiwalled carbon nanotube (MWCNT) modified gold electrode (Au-MWCNT@PANIpH7). The modified electrode showed highly redox active surface confined peaks corresponding to the molecular transitions of leucoemeraldine-emeraldine and emeraldine-pernigraniline in pH 7 phosphate buffered solution (PBS), along with a low capacitance behavior, in contrast to the conventional acidic solution PANI systems. Control experiments in the absence of MWCNTs (i.e., Au/PANIpH7) and in an acidic medium, pH 2 (i.e., Au-MWCNT@PANIpH2), resulted in nil and poor redox features respectively. The physicochemical characterization of the MWCNT@PANIpH7 film by TEM, Raman spectroscopy, FTIR and UV-Vis revealed the presence of polaron type PANI structures on the MWCNT surface. More interestingly, MWCNT@PANIpH7 showed a highly selective electrocatalytic signal to ascorbic acid (AA) at a low oxidation potential, -15 mV vs. Ag/AgCl, without interference from nitrite, uric acid, dopamine, glucose, cysteine and citric acid in pH 7 PBS. Extended flow injection analysis yielded an excellent AA sensing response with a detection limit (signal-to-noise ratio = 3) of 42 nM, which is better than that of the conventional acid assisted MWCNT@PANIpH2 and MWCNT systems.

Abstract: A newly developed porous polymer monolith was prepared through copolymerization of 3-(trimethoxysilyl)propylmethacrylate modified graphene oxide with glycidyl methacrylate and ethylene dimethacrylate as a functional crosslinker, which was synthesized through silanization reaction of graphene oxide prepared by Hummers method with 3-(trimethoxysilyl)propylmethacrylate. The monolith was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, mercury intrusion porosimetry and nitrogen adsorption measurement. The monolith column was applied as the stationary phase of high performance liquid chromatography and its chromatographic performance was evaluated by separation of small molecules in the isocratic reversed-phase mode. The chromatograms of hydrophobic steroids and polar aromatic amines on the prepared monolith displayed the enhanced separation performance over those on the parent monolith. The reproducibility of the column was less than 3.5% in terms of relative standard deviation of retention time. The results demonstrate that copolymerization of functionalized graphene oxide into porous polymer monolith was an effective tool for chromatography separation enhancement of small molecules in an isocratic mode.

Abstract: The bifunctionality of graphene oxide (GO) which can highly adsorb single-stranded DNA (ssDNA) and effectively quench the emission of organic dyes is reasonably utilized in a multiplexed DNA detection system, achieving sensitive and selective detection of HIV, VV and EV, respectively.

Abstract: Using molecular light switch Ru complex Ru(bpy)(2)(dppz)(2+) and CdTe quantum dots (QDs), we have designed a label-free DNA fluorescent sensor for the detection of Ag(+) in aqueous solution.

Abstract: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-acquired (HA-MRSA) infection worldwide. As a result, the rapid and specific detection of MRSA is crucial not only for early prevention of disease spread, but also for the effective treatment of these infections. We report here an integrated modular-based microfluidic system for MRSA identification, which can carry out the multi-step assay used for MRSA identification in a single disposable fluidic cartridge. The multi-step assay included PCR amplification of the mecA gene harboring methicillin resistance loci that can provide information on drug susceptibility, ligase detection reaction (LDR) to generate fluorescent ligation products appended with a zip-code complement that directs the ligation product to a particular address on a universal array containing zip-code probes and a universal DNA array, which consisted of a planar waveguide for evanescent excitation. The fluidic cartridge design was based on a modular format, in which certain steps of the molecular processing pipeline were poised on a module made from a thermoplastic. The cartridge was comprised of a module interconnected to a fluidic motherboard configured in a 3-dimensional network; the motherboard was made from polycarbonate, PC, and was used for PCR and LDR, while the module was made from poly(methylmethacrylate), PMMA, and contained an air-embedded waveguide serving as the support for the universal array. Fluid handling, thermal management and optical readout hardware were situated off-chip and configured into a small footprint instrument. In this work, the cartridge was used to carry out a multiplexed PCR/LDR coupled with the universal array allowed for simultaneous detection of five genes that encode for 16S ribosomal RNA (SG16S), protein A (spa), the femA protein of S. epidermidis (femA), the virulence factor of Panton-Valentine leukocidin (PVL) and the gene that confers methicillin resistance (mecA). Results indicated that this modular system could differentiate community-acquired MRSA (CA-MRSA) from hospital-acquired MRSA (HA-MRSA) based on the presence/absence of the PVL gene as well as S. aureus from other Staphylococcal species using the sequence content in the femA gene. This system can identify strains in <40 min and detect MRSA directly from a mixture of Staphylococci.

Abstract: Films of silver nanoparticles are used for the first time as an electrical conductor and ion-to-electron transducer to fabricate coated-wire ion selective electrodes (ISEs) on paper. The film of nano silver ink (nano silver film), synthesized from the reduction of AgNO3 by NaBH4, was screen printed on paper. Transmission electron microscopy showed that the synthesized silver nanoparticles (AgNPs) possessed a spherical shape with diameter ca. 5 nm. Energy-dispersive X-ray spectroscopy supported the purity and good stability of the synthesized AgNPs. Nano silver films were sintered at room temperature, 100 °C and 200 °C. Upon increasing the sintering temperature, atomic force microscopy showed that the size of AgNPs of nano silver films increased, but the sheet resistivity decreased. Silver ISEs were then fabricated from nano silver films and o-NPOE-plasticized polymeric membranes containing benzothiazolyl calix[4]arene () as ionophore and KTpClPB as anionic site. The performance of the developed Ag-ISEs was investigated by potentiometric measurements, potentiometric water layer tests, current reversal chronopotentiometry and electrochemical impedance spectroscopy. The coated-wire electrode fabricated from the nano silver film sintering at room temperature showed the best characteristics of Ag-ISEs giving a near Nernstian response slope of 59.7 ± 1.0 mV per decade, 10(-6) to 10(-2) M linear range, detection limit of 4.5 × 10(-7) M, long-term potential stability and good reversibility.

Abstract: Iridium complex is a lab-on-a-molecule for recognising and quantifying cysteine/homocysteine and tryptophan in a mixture of all proteinogenic amino acids. UV-Vis and photoluminescence channels are suitable for quantification of homocysteine and cysteine in aqueous media, e.g. by emission enhancement at 606 nm, while tryptophan was selectively quantified in the electrochemiluminescence channel.

Abstract: The direct interaction of hairpin DNA with 9-hydroxyfluorene (9-OHFLU) through hydrogen bonds was investigated by electrochemical impedance spectroscopy (EIS), UV-Vis spectroscopy and (1)H NMR spectra. Based on these results, an electrochemical hairpin DNA sensor was developed for the detection of 9-OHFLU by EIS. Upon 9-OHFLU interacting with hairpin DNA film on the gold electrodes, the charge transfer resistance (R(CT)) of the hairpin DNA film was significantly increased and remained constant after 30 min. Depending on the difference in charge transfer resistance (ΔR(CT)) before and after 9-OHFLU interaction with the hairpin DNA, 9-OHFLU could be detected with a concentration as low as 1 nM. However, only a much smaller ΔR(CT) appeared when eight selected hydroxyl polycyclic aromatic hydrocarbons (HO-PAHs) interacted with the hairpin DNA for 30 min, which demonstrated that 9-OHFLU could be discriminated from other HO-PAHs by EIS. The performance of the sensor in real lake water sample was further explored for the detection of 9-OHFLU with the detection limit of 4 nM.