Electrochemical microfluidic immunosensor with graphene-decorated gold nanoporous for T-2 mycotoxin detection

T-2 is one of the most potent cytotoxic food-borne mycotoxins. In this work, we have developed and characterized an electrochemical microfluidic immunosensor for T-2 toxin quantification in wheat germ samples. T-2 toxin detection was carried out using a competitive immunoassay method based on monoclonal anti-T-2 antibodies immobilized on the poly(methyl methacrylate) (PMMA) microfluidic central channel. The platinum wire working electrode at the end of the channel was in situ modified by a single-step electrodeposition procedure with reduced graphene oxide (rGO)-nanoporous gold (NPG). T-2 toxin in the sample was allowed to compete with T-2-horseradish peroxidase (HRP) conjugated for the specific recognizing sites of immobilized anti-T-2 monoclonal antibodies. The HRP, in the presence of hydrogen peroxide (H2O2), catalyzes the oxidation of 4-tert-butylcatechol (4-TBC), whose back electrochemical reduction was detected on the nanostructured electrode at -0.15 V. Thus, at low T-2 concentrations in the sample, more enzymatically conjugated T-2 will bind to the capture antibodies, and, therefore, a higher current is expected. The detection limits found for electrochemical immunosensor, and commercial ELISA procedure were 0.10 μg kg-1 and 10 μg kg-1, and the intra- and inter-assay coefficients of variation were below 5.35% and 6.87%, respectively. Finally, our microfluidic immunosensor to T-2 toxin will significantly contribute to faster, direct, and secure in situ analysis in agricultural samples.

Diagnostic Methods for Non-Falciparum Malaria

Malaria is a serious public health problem that affects mostly the poorest countries in the world, killing more than 400,000 people per year, mainly children under 5 years old. Among the control and prevention strategies, the differential diagnosis of the Plasmodium-infecting species is an important factor for selecting a treatment and, consequently, for preventing the spread of the disease. One of the main difficulties for the detection of a specific Plasmodium sp is that most of the existing methods for malaria diagnosis focus on detecting P. falciparum. Thus, in many cases, the diagnostic methods neglect the other non-falciparum species and underestimate their prevalence and severity. Traditional methods for diagnosing malaria may present low specificity or sensitivity to non-falciparum spp. Therefore, there is high demand for new alternative methods able to differentiate Plasmodium species in a faster, cheaper and easier manner to execute. This review details the classical procedures and new perspectives of diagnostic methods for malaria non-falciparum differential detection and the possibilities of their application in different circumstances.

Ultrasensitive microfluidic electrochemical immunosensor based on electrodeposited nanoporous gold for SOX-2 determination

An ultrasensitive and portable microfluidic electrochemical immunosensor for SOX-2 cancer biomarker determination was developed. The selectivity and sensitivity of the sensor were improved by modifying the microfluidic channel. This was accomplished through a physical-chemical treatment to produce a hydrophilic surface, with an increased surface to volume/ratio, where the anti-SOX-2 antibodies can be covalently immobilized. A sputtered gold electrode was used as detector and its surface was activated by using a dynamic hydrogen bubble template method. As a result, a gold nanoporous structure (NPAu) with outstanding properties, like high specific surface area, large pore volume, uniform nanostructure, good conductivity, and excellent electrochemical activity was obtained. SOX-2 present in the sample was bound to the anti-SOX-2 immobilized in the microfluidic channel, and then was labeled with a second antibody marked with horseradish peroxidase (HRP-anti-SOX-2) like a sandwich immunoassay. Finally, an H₂O₂ + catechol solution was added, and the enzymatic product (quinone) was reduced on the NPAu electrode at +0.1 V (vs. Ag). The current obtained was directly proportional to the SOX-2 concentration in the sample. The detection limit achieved was 30 pg mL^-1, and the coefficient of variation was less than 4.75%. Therefore, the microfluidic electrochemical immunosensor is a suitable clinical device for in situ SOX-2 determination in real samples.

Microfluidic immunosensor based on mesoporous silica platform and CMK-3/poly-acrylamide-co-methacrylate of dihydrolipoic acid modified gold electrode for cancer biomarker detection

We report a hybrid glass-poly (dimethylsiloxane) microfluidic immunosensor for epidermal growth factor receptor (EGFR) determination, based on the covalent immobilization of anti-EGFR antibody (anti-EGFR) on amino-functionalized mesoporous silica (AMS) retained in the central channel of a microfluidic device. The synthetized AMS was characterized by N₂ adsorption-desorption isotherm, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and infrared spectroscopy. The cancer biomarker was quantified in human serum samples by a direct sandwich immunoassay measuring through a horseradish peroxidase-conjugated anti-EGFR. The enzymatic product was detected at -100 mV by amperometry on a sputtering gold electrode, modified with an ordered mesoporous carbon (CMK-3) in a matrix of poly-acrylamide-co-methacrylate of dihydrolipoic acid (poly(AC-co-MDHLA)) through in situ copolymerization. CMK-3/poly(AC-co-MDHLA)/gold was characterized by cyclic voltammetry, EDS and SEM. The measured current was directly proportional to the level of EGFR in human serum samples. The linear range was from 0.01 ng mL^-1 to 50 ng mL^-1. The detection limit was 3.03 pg mL^-1, and the within- and between-assay coefficients of variation were below 5.20%. The microfluidic immunosensor is a very promising device for the diagnosis of several kinds of epithelial origin carcinomas.

Food safety control of zeranol through voltammetric immunosensing on Au–Pt bimetallic nanoparticle surfaces

This study reports an accurate and sensitive strategy for zeranol (ZER) determination in bovine urine samples.