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In this study, we developed a microfluidic chip integrated with on-chip valves for quantitative detection of biomarkers. The sandwich-structured microfluidic chip consists of a top fluidic layer embedded with a zigzag channel, a middle tinfoil layer pre-patterned with protein stripes, and a bottom substrate layer with two waste chambers. A set of customized on-chip valves was introduced for precise control of fluid flow. To improve the production volume and uniformity among chips, we selected an injection molding method for mass-production of the main components. We standardized the process of sealing chip layers and assembling the valve holder to improve the effectiveness of cooperation with the instrument. To demonstrate the versatility of the microfluidic chip for quantitative detection of biomarkers, we used it to automatically detect C-reactive proteins (CRP), interleukin-6 (IL-6), insulin, and osteocalcin with high sensitivity and excellent reproducibility inside a customized and portable instrument. We further conducted the automated chip-based chemiluminescence immunoassay to test CRP in serum samples for demonstration of potential clinical applications, assess the activity of capture antibodies of CRP (CRP-Ab 1 ) on the tinfoil layer for preliminary assessment of storage stability, and simultaneously detect CRP and IL-6 for confirmation of scalable multiplexation. This microfluidic chip for quantitative, automated, and portable immunoassay provides a promising choice for clinical practices.

This work describes the development, optimization and validation of a liquid chromatography-tandem mass spectrometric method (LC-MS/MS) for the simultaneous analysis of co-administered ranitidine (RAN) and metronidazole (MET) in plasma of healthy human volunteers. A simple protein precipitation procedure using 1 mL acetonitrile was applied to extract both drugs and metoclopramide as an internal standard (IS) from plasma. The chromatographic separation was achieved on a C 18 column with isocratic elution of the mobile phase consisting of acetonitrile and 0.1% formic acid (90?:?10, v/v) at a flow rate of 0.35 mL min ?1 . The positive ionization mode was used for detecting the ions, by observing the pairs of transition m / z 314.82 176.06 for RAN, m / z 172.03 127.95 for MET and m / z 299.86 277.10 for IS. The linearity range was from 5–600 ng mL ?1 for RAN and 2–40 μg mL ?1 for MET. The method was found to be sensitive and accurate with good simple extraction recovery and matrix effect, according to FDA guidelines for bioanalytical methods. The developed method could be applied for further bioavailability studies that could be useful in therapeutic drug monitoring.

A critical problem of many pathogen detection assays is the availability of intracellular protein and deoxyribonucleic acid (DNA). Acoustic lysis of suspended vegetative bacterial cells in a microfluidic system offers several advantages over conventional lysis techniques. The intracellular proteins and DNA are released and available for detection. A novel acoustic lysing alternative technique to the existing lysing methods for sample preparation and lysis step is proposed. We report here an efficient lysis device that uses acoustic excitation for performing lysis of Gram-positive and Gram-negative vegetative cells and has a high yield in a short amount of time. We also verified the condition of released protein since one of the major uses of vegetative cells lysis is for protein expression studies. Fluorimetry and flow cytometry were used to assess the degree of damage induced on the cells by the actual lysis method. The acoustic device allows the delivery of proteins in a non-denatured form, without adding chemicals, particles or other substances ( e.g. enzymes) that could complicate the process or the detection procedure. The lysis device operates at low power (50–400 mW) and short time (3 min) and has high efficiency in comparison to current lysis standards ( 85% vs. 12–50%).

In this study we describe a sensitive amperometric microbial biosensor that is fast, economic, reliable, and can compete with the existing proposed methods for vitamin B 12 determination. Taking advantage of the bacterial strain Tetrasphaera duodecadis which oxidizes vitamin B 12 with oxygen consumption, we shaped a promising alternative tool for the direct and specific determination of vitamin B 12 in different samples without pre-treatment. For this purpose, a vitamin B 12 amperometric microbial biosensor was constructed based on one-step immobilization of the bacterium by filtration of a concentrated bacterial mass through a 0.15 μm pore size cellulose filter and fixed on a Clark-type oxygen probe, serving as a transducer, and exploiting the described processes. The results obtained indicate a sensitive capability with a linear sensor concentration range from 10 ?7 mol L ?1 to 10 ?5 mol L ?1 and the response time of about 700 seconds at 10 ?6 mol L ?1 . Furthermore, the Tetrasphaera duodecadis membrane attached to the Clark type oxygen probe has an estimated 1 month lifetime at room temperature. In addition, the developed prototype allowed the assessment of B 12 status directly in samples prepared for that purpose. The results were well correlated with those obtained with commercial samples, thus demonstrating that the proposed microbial sensor offers an accurate and useful analytical tool that can be easily applied to prevent diseases caused by the lack of vitamin B 12 .

The facilitated transfer of alkali metal ions (Li + and Na + ) across the water/1,2-dichloroethane (W/ 1,2-DCE ) interface was studied by using a series of crown ethers as ionophores : 4′-ethynylbenzo-15-crown-5-ether ( L1 ), 3′,6′-diethynylbenzo-15-crown-5-ether ( L2 ) and 4′,5′-diethynylbenzo-15-crown-5-ether ( L3 ). Cyclic voltammetry was employed to study the electrochemical behaviour of the facilitated ion transfer across the W/1,2-DCE interface supported at the tip of a micropipette. The diffusion coefficients of the ionophores in the 1,2-DCE phase were determined, while the metal– ligand complexes formed by these ions with all the ionophores were obtained to be in a 1?:?1 stoichiometric ratio. The association constants, log β°, for complexes Li L1 + , Li L2 + , Li L3 + , Na L1 + , Na L2 + and Na L3 + were calculated to be 3.3, 4.2, 4.0, 2.1, 3.5 and 2.2, respectively. The theoretical calculations have shown that the conjugated constituent groups on the benzene ring have an essential effect on the spatial structures of the crown ether rings, which determine the supramolecular interaction between the ions and ionophores .

We provide here a user-friendly guide to find the optimum i-line (365 nm) photolithographic exposure dose of an arbitrary thickness of SU-8 on various substrate materials and thin film coatings used in MEMS, microsystems and microelectronics technologies: semiconductors, 2D materials (graphene and MoS 2 ) plastics, glass, metals and ceramics. By considering the variation of the absorption coefficient of SU-8 to ultraviolet light and the effect of partial reflections during the photolithography, we develop an analytical model for the exposure of SU-8. The critical exposure dose of the SU-8 enables a calculation of the exact greyscale photolithographic exposure time of the photoresist which optimizes the fabrication of microsystems structures (microcantilevers, microbridges, microchannels…) of a desired thickness. The optimum exposure doses are presented in both graphical and tabular format to enable user-friendly information based on the desired SU-8 thickness, the desired greyscale thickness and the specific wafer or coating used for the deposition. Interestingly, in the context of grey-scale lithography the model predicts that the surface reflectivity has a major impact on the resulting membrane thickness for a fixed dose and reducing the SU-8 thickness – on a highly reflecting surface a thicker membrane is obtained, on a low reflecting surface a thinner membrane in obtained when reducing the SU-8 thickness. The result is a useful guide for designers working with SU-8 in the context of many fabrication processes, e.g. MEMS, laboratory on a chip, microfluidics, microsystems, microengineering, micromoulding, and flexible electronics etc. – where a myriad of coatings and wafers are now used.

We report the generation of monoclonal antibodies against fenpropathrin, originating from a BALB/c mouse immunized with a conjugate of hapten 1 [(RS)-cyano-3-phenoxybenzyl-2,2,3,3-tetramethylcyclopropane-carboxylic acid)] and keyhole limpet hemocyanin and the establishment of a monoclonal antibody-based immunochromatographic test strip. A coating antigen (test band) and a goat anti-mouse antibody (control band) were separately immobilized on nitrocellulose membrane strips as capture reagents. The anti-fenpropathrin monoclonal antibody was labeled with gold nanoparticles as a detection probe. This test strip had a wide linear range (15.6–250 μg L ?1 ) with a low detection limit of 62 ± 6 μg L ?1 for fenpropathrin, evaluated using a strip reader, and could be read within 10 min. This novel test strip was used to test fenpropathrin in fortified samples and found to have a high recovery rate ( 80%). In summary, our monoclonal antibody-based immunochromatographic strip offers a rapid screening tool for fenpropathrin detection in agricultural commodities.

The development of simple and reproducible analytical methods for the determination of new organic pollutants like pharmaceuticals and personal care products in seawaters is of the highest priority. In the present study, a new analytical method based on offline solid phase extraction and liquid chromatography with standard UV detection (SPE-HPLC-UV) was developed to determine the presence of sulfonamides in seawaters. Special attention was paid to the sample preparation step. Different variables affecting the extraction process, such as seawater salinity and the humic acid content were studied. As a result, the presented SPE procedure for the extraction of sulfonamides from seawaters is also applicable to other techniques like LC-MS and LC-MS/MS. This method was optimized and fully validated for its performance parameters. It has very good selectivity, linearity ( R 2 0.995), precision ( RSD 5%), accuracy (76.7–115.4%), as well as low limits of detection (LOD, 167 ng L ?1 ) and quantification (LOQ, 500 ng L ?1 ). This SPE procedure proved to be very effective (absolute recovery 75%), even in highly saline waters and in the presence of humic acids.

A simple and reliable voltammetric sensor for simultaneous determination of hydroquinone (HQ) and catechol (CC) was developed on an electrochemically activated glassy carbon electrode (GCE). The cyclic voltammograms in a mixed solution of HQ and CC have shown that the oxidation peaks become well resolved and were separated by 108 mV, although the bare GCE gave a single broad oxidation peak. Moreover, the oxidation peak currents of both HQ and CC were remarkably increased at the electrochemically activated GCE, which makes it suitable for simultaneous determination of these isomers. In the presence of 5.0 × 10 ?5 mol L ?1 isomer, the oxidation peak currents of square wave voltammograms are proportional to the concentration of HQ in the range of 1.0 × 10 ?6 to 1.0 × 10 ?4 mol L ?1 , and to that of CC in the range of 2.0 × 10 ?6 to 1.0 × 10 ?4 mol L ?1 . The corresponding detection limits for HQ and CC are as low as 1.8 × 10 ?8 and 3.2 × 10 ?8 mol L ?1 (S/N = 3), respectively.

The proposed work introduces an electrochemical sensor based on an Fe 3 O 4 /Ag nanocomposite for highly sensitive and selective electrochemical determination of dicyclomine hydrochloride (DcCl) using adsorptive stripping square wave voltammetry (AdSSWV). A nanocomposite of silver decorated Fe 3 O 4 nanocubes has been synthesized using a facile sonochemical method. The prepared nanocomposite was characterized using various characterization techniques. The impact of various parameters such as pH, scan rate, accumulation potential and accumulation time on peak current was studied employing different techniques including differential pulse voltammetry (DPV), cyclic voltammetry (CV) and AdSSWV. Under the optimized conditions, the peak current is found to be linearly proportional to the DcCl concentration in a wide linear working range from 2.0 × 10 ?7 to 8.0 × 10 ?4 M with a limit of detection (LOD) and a limit of quantification (LOQ) of 4.8 × 10 ?9 M and 1.6 × 10 ?8 M, respectively. The fabricated sensor exhibited high sensitivity and selectivity along with good stability and reproducibility, and therefore the proposed method can serve as an excellent platform for the determination of DcCl at the nanomolar level with adequate recovery in pharmaceutical as well as biological samples.