Gold electrode modified by self-assembled monolayers of thiols to determine DNA sequences hybridization

The process of immobilization of biological molecules is one of the most important steps in the construction of a biosensor. In the case of DNA, the way it exposes its bases can result in electrochemical signals to acceptable levels. The use of self-assembled monolayer that allows a connection to the gold thiol group and DNA binding to an aldehydic ligand resulted in the possibility of determining DNA hybridization. Immobilized single strand of DNA (ssDNA) from calf thymus pre-formed from alkanethiol film was formed by incubating a solution of 2-aminoethanothiol (Cys) followed by glutaraldehyde (Glu). Cyclic voltammetry (CV) was used to characterize the self-assembled monolayer on the gold electrode and, also, to study the immobilization of ssDNA probe and hybridization with the complementary sequence (target ssDNA). The ssDNA probe presents a well-defined oxidation peak at +0.158 V. When the hybridization occurs, this peak disappears which confirms the efficacy of the annealing and the DNA double helix performing without the presence of electroactive indicators. The use of SAM resulted in a stable immobilization of the ssDNA probe, enabling the hybridization detection without labels. This study represents a promising approach for molecular biosensor with sensible and reproducible results

Cobalt phthalocyanine as a biomimetic catalyst in the amperometric quantification of dipyrone using FIA

A biomimetic sensor for the determination of dipyrone was prepared by modifying carbon paste with cobalt phthalocyanine (CoPc), and used as an amperometric detector in a flow injection analysis (FIA) system. The results of cyclic voltammetry experiments suggested that CoPc behaved as a biomimetic catalyst in the electrocatalytic oxidation of dipyrone, which involved the transfer of one electron. The optimized FIA procedure employed a flow rate of 1.5 mL min(-1), a 75 mu L sample loop, a 0.1 mol L-1 phosphate buffer carrier solution at pH 7.0 and amperometric detection at a potential of 0.3 V vs. Ag/AgCl. Under these conditions, the proposed method showed a linear response for dipyrone concentrations in the range 5.0 x 10(-6)-6.3 x 10(-3) mol L-1. Selectivity and interference studies were carried out in order to validate the system for use with pharmaceutical and environmental samples. In addition to being environmentally friendly, the proposed method is a sensitive and selective analytical tool for the determination of dipyrone. (C) 2011 Elsevier B.V. All rights reserved

A Methylene Blue-Enhanced Nanostructured Electrochemical Immunosensor for H-FABP Myocardial Injury Biomarker

A sensitive electrochemical immunosensor for the detection of the heart-type fatty acid binding protein (HFABP), an earlier biomarker for acute myocardial infarction than Troponins, is described. The sensing platform was enhanced with methylene blue (MB) redox coupled to carbon nanotubes (CNT) assembled on a polymer film of polythionine (PTh). For this strategy, monomers of thionine rich in amine groups were electrosynthesized by cyclic voltammetry on the immunosensor’s gold surface, forming an electroactive film with excellent electron transfer capacity. Stepwise sensor surface preparation was electrochemically characterized at each step and scanning electronic microscopy was carried out showing all the preparation steps. The assembled sensor platform combines MB and PTh in a synergism, allowing sensitive detection of the H-FABP in a linear response from 3.0 to 25.0 ng∙mL−1 with a limit of detection of 1.47 ng∙mL−1 HFABP that is similar to the clinical level range for diagnostics. H-FABP is a newer powerful biomarker for distinguishing between unstable angina and acute myocardial infarction

Development and application of a screen-printed electrode modified with MWCNT for the electrocatalytic detection of thiram

Interest in the electronic properties of carbon nanotubes has increased in recent years. These materials can be used in the development of electrochemical sensors for the measurement and monitoring of analytes of environmental interest, such as pharmaceuticals, dyes, and pesticides. This work describes the use of homemade screen-printed electrodes modified with multi-walled carbon nanotubes (MWCNT) for the electrochemical detection of the fungicide thiram. The electrochemical characteristics of the proposed system were evaluated using cyclic voltammetry, with investigation of the electrochemical behavior of the sensor in the presence of the analyte, and estimation of electrochemical parameters including the diffusion coefficient, electron transfer coefficient (α), and number of electrons transferred in the catalytic electro-oxidation. The sensor response was optimized using amperometry. The best sensor performance was obtained in 0.1 mol L-1 phosphate buffer solution at pH 8.0, where a detection limit of 7.9 x 10-6 mol L-1 was achieved. Finally, in order to improve the sensitivity of the sensor, square wave voltammetry (SWV) was used for thiram quantification, instead of amperometry. Using SWV, a response range for thiram from 9.9 x 10-6 to 9.1 x 10-5 mol L-1 was obtained, with a sensitivity of 30948 µA mol L-1, and limits of detection and quantification of 1.6 x 10-6 and 5.4 x 10-6 mol L-1, respectively. The applicability of this efficient new alternative methodology for thiram detection was demonstrated using analyses of enriched soil samples

Wearable Technology for One Health: Charting the course of Dermal Biosensing

Over the last decade, a significant paradigm shift has been observed towards leveraging less invasive biological fluids— such as skin interstitial fluid (ISF), sweat, tears, and saliva—for health monitoring. This evolution seeks to transcend traditional, invasive blood-based methods, offering a more accessible approach to health monitoring for non-specialized personnel. Skin ISF, with its profound resemblance to blood, emerges as a pivotal medium for the real-time, minimally invasive tracking of a broad spectrum of biomarkers, thus becoming an invaluable asset for correlating with blood-based data. Our exploration delves deeply into the development of wearable molecular biosensors, spotlighting dermal sensors for their pivotal roles across both clinical and everyday health monitoring scenarios and underscoring their contributions to the holistic One Health initiative. In bringing forward the myriad challenges that permeate this field, we also project future directions, notably the potential of skin ISF as a promising candidate for continuous health tracking. Moreover, this paper aims to catalyse further exploration and innovation by presenting a curated selection of seminal technological advancements. Amidst the saturated landscape of analytical literature on translational challenges, our approach distinctly seeks to highlight recent developments. In attracting a wider spectrum of research groups to this versatile domain, we endeavour to broaden the collective understanding of its trajectory and potential, mapping the evolution of wearable biosensor technology. This strategy not only illuminates the transformative impact of wearable biosensors in reshaping health diagnostics and personalized medicine but also fosters increased participation and progress within the field. Distinct from recent manuscripts in this domain, our review serves as a distillation of key concepts, elucidating pivotal papers that mark the latest advancements in wearable sensors. Through presenting a curated collection of landmark studies and offering our perspectives on the challenges and forward paths, this paper seeks to guide new entrants in the area. We delineate a division between wearable epidermal and subdermal sensors—focusing on the latter as the future frontier—thereby establishing a unique discourse within the ongoing narrative on wearable sensing technologies

Produção de anticorpos policlonais anti-ricina Production of polyclonal anti-ricin antibodies

A ricina é uma proteína bastante tóxica presente nas sementes de mamona que impossibilita o uso da torta de mamona "in natura", como ração. A torta de mamona destoxificada necessita ainda de métodos de análise que garantam a ausência de traços dessa proteína. Objetivou-se, neste trabalho, produzir e avaliar a sensibilidade e especificidade de anticorpos policlonais anti-ricina, para serem empregados como possíveis componentes de métodos sorológicos na detecção de ricina em torta de mamona destoxificada. Foram avaliadas três doses da proteína: 400, 180 e 100 µg cada uma dividida em duas aplicações em coelhos. A primeira dose foi injetada no animal no início do experimento e a segunda após 21 dias. O método de ELISA indicou que as duas doses menores (100 e 180 µg) induziram respostas imunológicas primária e secundária com produção de anticorpos específicos. Enquanto a dose maior (400 µg) de ricina apresentou uma resposta primária com elevação dos títulos de anticorpos, seguida de uma supressão da resposta. Esse perfil é sugestivo de tolerância imunológica. Pela técnica de Western blotting verificou-se que os anticorpos policlonais produzidos são bastante específicos para a ricina, no entanto, por detectarem ricina na forma nativa e desnaturada não são recomendados para o monitoramento de ricina em torta de mamona destoxificada por tratamento térmico.Ricin is a very toxic protein found in castor bean plants, making it impossible to use natural castor cake as animal food. The detoxificated castor cake needs to be analyzed by methods that ensure the absence of traces of this protein. This work had the objective to produce and to evaluate the sensitivity and specificity of anti-ricin polyclonal antibodies, to be employed as component of sorologic methods as the ELISA in the detection of ricin in detoxificated castor cake. Three doses of protein, 400, 180 and 100 µg were evaluated each one injected twice into rabbit, with one half in the begin of the experiment and the other half after 21 days of immunization. The ELISA method indicated that the lower doses (100 e 180 µg) induced primary and secondary immunological response with production of specific antibodies, while the higher dose of ricin (400 µg) showed a primary response with increase of the antibody titre, followed of immunological suppression. This profile suggests immunological tolerance. By Western blotting technique it was verified that polyclonal antibodies are too specific to ricin, however, they detected ricin in native and denaturated form and are not recommended for the monitoring of ricin in detoxificated castor bean cake by heat treatment

A Redox-Probe-Free Immunosensor Based on Electrocatalytic Prussian Blue Nanostructured Film One-Step-Prepared for Zika Virus Diagnosis

The Zika virus (ZIKV) is a great concern for global health due to its high transmission, including disseminating through blood, saliva, urine, semen and vertical transmission. In some cases, ZIKV has been associated with microcephaly, neurological disorders, and Guillain–Barré syndrome. There is no vaccine, and controlling the disease is a challenge, especially with the co-circulation of the Dengue virus, which causes a severe cross-reaction due to the similarity between the two arboviruses. Considering that electrochemical immunosensors are well-established, sensitive, and practical tools for diagnosis, in this study we developed a sensor platform with intrinsic redox activity that facilitates measurement readouts. Prussian blue (PB) has a great ability to form electrocatalytic surfaces, dispensing redox probe solutions in voltammetric measurements. Herein, PB was incorporated into a chitosan–carbon nanotube hybrid, forming a nanocomposite that was drop-casted on a screen-printed electrode (SPE). The immunosensor detected the envelope protein of ZIKV in a linear range of 0.25 to 1.75 µg/mL (n = 8, p < 0.01), with a 0.20 µg/mL limit of detection. The developed immunosensor represents a new method for electrochemical measurements without additional redox probe solutions, and it is feasible for application in point-of-care diagnosis

IMMUNOSENSOR BASED ON INK PRINTED ELECTRODE FOR STAPHYLOCOCCAL ENTEROTOXIN DETECTIONdoi: http://dx.doi.org/10.5892/ruvrd.v12i1.1400

Staphylococcal enterotoxin is one of the more aggressive enterotoxins produced by Staphylococcus aureus strains and it is a common cause of food poisoning. Analytical methods that are sensitive, low cost and easy to use are needed to evaluate the food quality. This work describes the development of a label free immunosensor based on screen-printed AuNPs/carbon and the characterization of its analytical response for staphylococcal enterotoxin B (SEB) detection. The biosensor was constructed from self-assembled monolayer of thiols and protein A for the oriented immobilization of the polyclonal antibodies against SEB. As electrons mediator, potassium ferrocyanide was used. The electrochemical detection was direct with the parameters following: -0.2 to 0.6 V with the pulse amplitude of 0.075 V and the pulse width of 75 ms. The immunosensor showed detection and quantification limits of 0.4 µg mL-1 and 1.6 µg mL-1,respectively. The immunosensor showed quite satisfactory performance in contaminated and non-contaminated cheese samples