Synthesis and characterization of a nanostructure conductive copolymer based on polyaniline and polylactic acid as an effective substrate in proteins impedimetric biosensing.

Despite of all the developments in DNA microarray technology, there is not sufficient knowledge about protein abundance or their function in processes such as proteolysis, phosphorylation. Therefore, there is a significant need for direct detection and quantification of proteins, especially in processes such as proteomics, drug design and disease prediction. The present work introduce the new generation of polymeric substrate based on polyaniline and, polylactic acid, which it was used for impedimetric sensor in detection of proteins in particular for bovine serum albumin (BSA). In this copolymerization, the polylactic acid-block-polyaniline copolymer (PLA-b-PANI) was synthesized to attach polylactic acid and polyaniline using epichlorohydrin as a coupling agent. The structure of synthesized compounds in all steps, were confirmed by FT-IR and, 1H-NMR. The thermal properties and, morphology were analyzed by DSC, TGA, and, SEM. Also the electrochemical characteristics of fabricated PLA-b-PANI electrode were investigated by Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The results demonstrated that morphology of the PLA-b-PANI is sphere shape nanoparticles with dimension less than 100 nanometer diameters and, reasonable thermal properties. PLA-b-PANI was used to modify a screen-printed carbon electrode (SPCE) to fabricate a BSA impedimetric sensor. In order to increase the performance of the proposed impedimetric sensor, optimization of incubation time, pH and amount of PLA-b-PANI were investigated. The results show that the impedimetric sensor has the highest response when the electrode surface is covered with 5 microliters of PLA-b-PANI, and is incubated in BSA solution with pH 6.5 for 5 min. Impedimetric results showed that the PLA-b-PANI has excellent properties in reducing the charge transfer resistance and increasing the electron charge transfer rate. The final impedimetric sensor exhibited good repeatability, reproducibility, and chemical stability within the linear concentration range of 0.1-20 µg L-1 of BSA, and a detection limit of 0.05 µg L-1.

Preconcentration and determination of five antidepressants from human milk and urine samples by stir bar filled magnetic ionic liquids using liquid-liquid-liquid microextraction-high-performance liquid chromatography.

A sensitive and straightforward liquid-liquid-liquid microextraction method was developed to preconcentrate and cleanup antidepressants, including mirtazapine, venlafaxine, escitalopram, fluoxetine, and fluvoxamine, from biological samples before analyzing with high-performance liquid chromatography. The essential novelty of this study is using magnetic ionic liquids as the extraction phase in the lumen of hollow fiber and preparing a liquid magnetic stir bar. In this method, polypropylene hollow fiber was utilized as the permeable membrane for the analyte extraction. Six magnetic ionic liquids consisting of the transition metal and rare earth compounds were synthesized and then hollow fiber lumen was injected as acceptor phase to extract the antidepressants. Besides, 3-pentanol as a water-immiscible solvent was impregnated in the hollow fiber wall pores. The effective factors in the method were optimized with the central composition design. The resultant calibration curves were linear over the concentration range of 0.8-400.0 ng mL-1 (R2 ≥ 0.996). The method displayed the proper detection limit (0.11-0.24 ng mL-1 ), the reasonable limit of quantification (≤0.79 ng mL-1 ), wide linear ranges, high preconcentration factors (≥294.3), and suitable relative standard deviation (2.31-5.47%) for measuring antidepressant medications. Analysis of human milk and urine samples showed acceptable recoveries of 96.5-103.8% with excellent relative standard deviations lower than 5.95%.

An ultrasensitive platform for PCB77 detection: New strategy for liquid crystal-based aptasensor fabrication.

Polychlorinated biphenyls (PCBs) are considered persistent bio-accumulative toxicants which threats global food safety and environmental health. Traditional analytical techniques for detection of PCBs are time-consuming and they do not satisfy urgent need for rapid and accurate monitoring of these persistent pollutants. Biosensor technology may be promising in this respect. Here we demonstrate a novel liquid crystal (LC)-based aptasensing platform as a promising label-free and rapid biosensor for PCB77 detection. This novel molecular strategy utilize triple-helix molecular conformational switch which is mediated formation of duplex on sensing platform in presence of target. Duplex forming leads to optical change from dark to bright in a liquid crystal based aptasensor. The limit of quantification of the LC-aptasensor to PCB77 is 1.5 × 10-5 µg/L with comparable selectivity. Besides, we also demonstrated that this system is able to detect PCB77 in tap water, environmental water and milk. This strategy has potential for label-free and portable detection of different targets without any aptamer sequence length restrictions.

Recent progress in the development of recognition bioelements for polychlorinated biphenyls detection: Antibodies and aptamers.

Polychlorinated biphenyls (PCBs) are persistent pollutants, which have expanded in foods and the environment. Detection of PCBs is considered essential due to recognized side-effects of PCBs on health and the public concerns in this regard. On the other hand, due to the trace levels of these organic chlorine compounds, reliable and sensitive assays must be developed. Recognition elements are essential parts of analytical detection assays and sensors of PCBs since these elements are involved in the selective identification of the analytes of interest. Understanding the fundamentals of the recognition elements of PCBs and the benefits of the sensor strategies result in the development of next-generation recognition devices. This review aimed to highlight the recent progress in the recognition elements as key parts of biosensors. We initially, focused on the developed antibody-based biosensors for the detection of PCBs, followed by discussing the aptamers as novel recognition elements. Furthermore, the recent advancement in the development of aptamer-based solid phase extractions has been evaluated. These findings could contribute to improving the design of commercial PCB-kits in the future.

A new amperometric biosensor based on Fe3O4/polyaniline/laccase/chitosan biocomposite-modified carbon paste electrode for determination of catechol in tea leaves.

In the present study, a new biosensor based on laccase from Paraconiothyrium variabile was developed for catechol. The purified enzyme entrapped into the Fe3O4/polyaniline/chitosan (Fe3O4/polyaniline (PANI)/chitosan (CS)) biocomposite matrix film without the aid of other cross-linking reagents by a one-step electrodeposition on the surface of carbon paste electrode (CPE). The formed layer of biocomposite was characterized with scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The biosensor was optimized with respect to biocomposite composition, enzyme loading, and solution pH by amperometry method. The biosensor exhibited noticeable eletrocatalytic ability toward catechol with a linear concentration range from 0.5 to 80 µM and a detection limit of 0.4 µM. The biosensor showed optimum response within 8 s, at pH 5, and 40 °C. The apparent Michaelis-Menten (K M (app)) was found to be 1.092 µM. The fabricated biosensor could be applied for determination of catechol in tea leaf samples.

A nanocomposite/crude extract enzyme-based xanthine biosensor.

A novel amperometric biosensor for xanthine was developed based on covalent immobilization of crude xanthine oxidase (XOD) extracted from bovine milk onto a hybrid nanocomposite film via glutaraldehyde. Toward the preparation of the film, a stable colloids solution of core-shell Fe3O4/polyaniline nanoparticles (PANI/Fe3O4 NPs) was dispersed in solution containing chitosan (CHT) and H2PtCl6 and electrodeposited over the surface of a carbon paste electrode (CPE) in one step. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrophotometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used for characterization of the electrode surface. The developed biosensor (XOD/CHT/Pt NPs/PANI/Fe3O4/CPE) was employed for determination of xanthine based on amperometric detection of hydrogen peroxide (H2O2) reduction at -0.35V (vs. Ag/AgCl). The biosensor exhibited a fast response time to xanthine within 8s and a linear working concentration range from 0.2 to 36.0µM (R(2)=0.997) with a detection limit of 0.1µM (signal/noise [S/N]=3). The sensitivity of the biosensor was 13.58µAµM(-1)cm(-2). The apparent Michaelis-Menten (Km) value for xanthine was found to be 4.7µM. The fabricated biosensor was successfully applied for measurement of fish and chicken meat freshness, which was in agreement with the standard method at the 95% confidence level.

A novel spectrophotometric method for determination of kinetic constants of aldehyde oxidase using multivariate calibration method.

Although phenanthridine has been frequently used as a specific substrate for the assessment of aldehyde oxidase activity, the use of this method is questionable due to a lower limit of detection and its validity for kinetic studies. In the present study, a novel sensitive multivariate calibration method based on partial least squares (PLS) has been developed for the measurement of aldehyde oxidase activity using phenanthridine as a substrate. Phenanthridine and phenanthridinone binary mixtures were prepared in a dynamic linear range of 0.1-30.0 microM and the absorption spectra of the solutions were recorded in the range of 210-280 nm in Sorenson's phosphate buffer (pH 7.0) containing EDTA (0.1 mM). The optimized PLS calibration model was used to calculate the concentration of each chemical in the prediction set. Hepatic rat aldehyde oxidase was partially purified and the initial oxidation rates of different concentrations of phenanthridine were calculated using the PLS method. The values were used for calculating Michaelis-Menten constants from a Lineweaver-Burk double reciprocal plot of initial velocity against the substrate concentration. The limits of detection for phenanthridine and phenanthridinone were found to be 0.04+/-0.01 and 0.03+/-0.01 microM (mean+/-SD, n=5), respectively. Using this method, the Km value for the oxidation of phenanthridine was calculated as 1.72+/-0.09 microM (mean+/-SD, n=3). Thus, this study describes a novel spectrophotometric method that provides a suitable, sensitive and easily applicable means of measuring the kinetics of phenanthridine oxidation by aldehyde oxidase without the need for expensive instrumentation.