Acetylcholinesterase inhibition-based biosensor for aluminum(III) chronoamperometric determination in aqueous media

Urease combined with CdSe quantum dots as an enzyme sensor for quantitative detection of some metals in water

This investigation illustrates the potential role of urease as an enzymatic sensor in conjunction with CdSe quantum dots (QDs) for the detection of various metals present in aqueous environments. The enzyme urease catalyzes the hydrolysis of urea, resulting to the production of carbon dioxide and ammonia. The formation of ammonia leads to an increase in the pH of the solution, which in turn enhances the fluorescence of the CdSe quantum dots. In contrast, the presence of different metal can inhibit enzyme activity, thereby reducing ammonia production, which results in less pronounced pH changes and a subsequent increase in the fluorescence of the QDs. These variations are dependent on the concentration of the metals, allowing for the detection of several metals in water. This method enables the identification of metals such as Cu, Co, Mg, Fe, Cr, Zn, and Ni, with a detection limit of 0.2 μM. This level of sensitivity is adequate for evaluating the safety of water intended for various food products.

Is Postoperative Adjuvant Transcatheter Arterial Infusion Therapy Effective for Patients with Hepatocellular Carcinoma who Underwent Hepatectomy? A Prospective Randomized Controlled Trial

BACKGROUND

The effectiveness of adjuvant transcatheter arterial chemo- or/and chemoembolization therapy after curative hepatectomy of initial hepatocellular carcinoma (HCC) is controversial. This study aimed to evaluate whether hepatectomy combined with adjuvant transcatheter arterial infusion therapy (TAI) for initial HCC has better long-term survival outcomes than hepatectomy alone.

METHODS

From January 2012 to December 2014, a prospective randomized controlled trial of patients with initial HCC was conducted. Then, 114 initial HCC patients were recruited to undergo hepatectomy with adjuvant TAI (TAI group, n = 55) or hepatectomy alone (control group, n = 59) at our institution. The TAI therapy was performed twice, at 3 and 6 months after curative hepatectomy (UMIN 000011900).

RESULTS

The patients treated with TAI had no serious side effects, and operative outcomes did not differ between the two groups. No significant differences were found in the pattern of intrahepatic recurrence or time until recurrence between the two groups. Moreover, no significant differences were found in the relapse-free survival or overall survival. Low cholinesterase level (< 200) had been identified as a risk factor affecting relapse-free survival. Furthermore, compared with surgery alone, adjuvant TAI with hepatectomy improved the overall survival for lower-cholinesterase patients.

CONCLUSIONS

Adjuvant TAI is safe and feasible, but it cannot reduce the incidence of postoperative recurrence or prolong survival for patients who underwent curative hepatectomy for initial HCC.

Quantitative Determining of Ultra-Trace Aluminum Ion in Environmental Samples by Liquid Phase Microextraction Assisted Anodic Stripping Voltammetry

Direct detecting of trace amount Al(III) in aqueous solution by stripping voltammetry is often frustrated by its irreversible reduction, resided at &minus;1.75 V (vs. Ag/AgCl reference), which is in a proximal potential of proton reduction. Here, we described an electroanalytical approach, combined with liquid phase microextraction (LPME) using ionic liquid (IL), to quantitatively assess trace amount aluminum in environmental samples. The Al(III) was caged by 8-hydroxyquinoline, forming a superb hydrophobic metal⁻chelate, which sequentially transfers and concentrates in the bottom layer of IL-phase during LPME. The preconcentrated Al(III) was further analyzed by a square-wave anodic stripping voltammetry (SW-ASV). The resulting Al-deposited electrodes were characterized by scanning electron microscopy and powder X-ray diffraction, showing the intriguing amorphous nanostructures. The method developed provides a linear calibration ranging from 0.1 to 1.2 ng L^&minus;1 with a correlation coefficient of 0.9978. The LOD attains as low as 1 pmol L^&minus;1, which reaches the lowest report for Al(III) detection using electroanalytical techniques. The applicable methodology was implemented for monitoring Al(III) in commercial distilled water.

Design and Development of Acetylthiocholine Electrochemical Biosensor Based on Zinc Oxide-Cerium Oxide Nanohybrid Modified Platinum Electrode

Acetylcholinesterase (AChE) enzyme has been predominantly used for the detection of pesticides and metal ions. But, these sensors respond to pesticides as well as metal ions at certain concentration, which results in poor selectivity. Hence in this work, the amount of thiocholine produced during AChE inhibition has been estimated to detect the residual activity of AChE enzyme in-turn to enhance the efficiency of the biosensor. In this context, Pt/ZnO-CeO₂/AChE/Chitosan based biosensor has been developed for sensitive voltammetric quantification of thiocholine in AChE. The sensor exhibited enhanced electron transfer rate, good conductivity and biocompatibility. Both the intrinsic and extrinsic parameters were simultaneously optimized using second order polynomial regression to get the best conditions for ATCh determination. Under optimized experimental conditions, the redox peak current was linear over the concentration range of 0.1-1.5 mM with detection and quantification limit of 0.05 and 0.15 μM respectively and the sensitivity of 1.47 μA mM^-1.

Functional nanostructures for enzyme based biosensors: properties, fabrication and applications

A review describing functional nanostructures for portable and printable enzyme biosensors. Specific physicochemical and surface properties of nanoparticles used as carriers and sensing components and their assembly are discussed with an overview of current and emerging techniques enabling large scale roll-to-roll fabrication and miniaturization. Their integration in flexible, wearable and inexpensive point-of-use devices, and implementation challenges are also provided with examples of applications.

Recent advances in biosensors based on enzyme inhibition

Enzyme inhibitors like drugs and pollutants are closely correlated to human and environmental health, thus their monitoring is of paramount importance in analytical chemistry. Enzymatic biosensors represent cost-effective, miniaturized and easy to use devices; particularly biosensors based on enzyme inhibition are useful analytical tools for fast screening and monitoring of inhibitors. The present review will highlight the research carried out in the last 9 years (2006-2014) on biosensors based on enzyme inhibition. We underpin the recent advances focused on the investigation in new theoretical approachs and in the evaluation of biosensor performances for reversible and irreversible inhibitors. The use of nanomaterials and microfluidic systems as well as the applications of the various biosensors in real samples is critically reviewed, demonstrating that such biosensors allow the development of useful devices for a fast and reliable alarm system.

Amperometric bioaffinity sensing platform for avian influenza virus proteins with aptamer modified gold nanoparticles on carbon chips

A sandwich assay platform involving a surface formed aptamer-protein-antibody complex was developed to obtain the highly selective and sensitive amperometric detection of H5N1 viral proteins using a gold nanoparticle (NP) modified electrode. This is the first aptamer-antibody pairing reported for the selective detection of H5N1. Nanoparticle deposited screen-printed carbon electrodes were first functionalized by the covalent immobilization of a DNA aptamer specific to H5N1 followed by the adsorption of H5N1 protein. Alkaline phosphatase (ALP) conjugated monoclonal antibody was then adsorbed to form a surface bound Au NPs-aptamer/H5N1/antiH5N1-ALP sandwich complex which was further reacted with the enzyme substrate, 4-amino phenyl phosphate (APP). The current associated with the electrocatalytic reaction of the surface bound ALP with APP increased as the H5N1 concentration increased. A lowest detectable concentration of 100 fM was obtained with a linear dynamic range of 100 fM to 10 pM using differential pulse voltammetry. As an example, the biosensor was applied to the detection of H5N1 protein in diluted human serum samples spiked with different concentrations of the viral protein target.

Simple mass spectrometric method for the estimation of boron and aluminum in water at the parts per billion level

The coordinating nature of the hydroxy carboxylic acids, such as tartaric and citric acids, has been utilized for the in-situ formation of anions representing the trivalent elements boron and aluminum and two dianions of the hydroxy acid selected under negative electrospray ionization mass spectral conditions. The abundance of these ions could be used for the quantification of boron and aluminum in water at concentrations ranging from 4.0 ppb to 535.0 ppb. For a period of six months, the validity of this method was tested with citric acid as the coordinating agent. Thus, the developed method offers a simple means for the quantification of boron and aluminum in water by negative electrospray ionization mass spectrometry with a single quadrupole mass spectrometer.

Nanomaterials-based optical techniques for the detection of acetylcholinesterase and pesticides

The large amount of pesticide residues in the environment is a threat to global health by inhibition of acetylcholinesterase (AChE). Biosensors for inhibition of AChE have been thus developed for the detection of pesticides. In line with the rapid development of nanotechnology, nanomaterials have attracted great attention and have been intensively studied in biological analysis due to their unique chemical, physical and size properties. The aim of this review is to provide insight into nanomaterial-based optical techniques for the determination of AChE and pesticides, including colorimetric and fluorescent assays and surface plasmon resonance.