•A label-free flexible biodevice applicable to COVID-19 was developed.•Flexible transducers were modified with polypyrrole films and gold nanoparticles.•The sensor showed a limit of detection of ...258.01 copies µL−1 with high selectivity.•The resistance variation was associated with the cycle threshold value of RT-PCR.•SARS-CoV-2 diagnosis was correlated with various stages of the viral infection.
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The projection of new biosensing technologies for genetic identification of SARS-COV-2 is essential in the face of a pandemic scenario. For this reason, the current research aims to develop a label-free flexible biodevice applicable to COVID-19. A nanostructured platform made of polypyrrole (PPy) and gold nanoparticles (GNP) was designed for interfacing the electrochemical signal in miniaturized electrodes of tin-doped indium oxide (ITO). Oligonucleotide primer was chemically immobilized on the flexible transducers for the biorecognition of the nucleocapsid protein (N) gene. Methodological protocols based on cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM) were used to characterize the nanotechnological apparatus. The biosensor’s electrochemical performance was evaluated using the SARS-CoV-2 genome and biological samples of cDNA from patients infected with retrovirus at various disease stages. It is inferred that the analytical tool was able to distinguish the expression of SARS-CoV-2 in patients diagnosed with COVID-19 in the early, intermediate and late stages. The biosensor exhibited high selectivity by not recognizing the biological target in samples from patients not infected with SARS-CoV-2. The proposed sensor obtained a linear response range estimated from 800 to 4000 copies µL−1 with a regression coefficient of 0.99, and a detection limit of 258.01 copies µL−1. Therefore, the electrochemical biosensor based on flexible electrode technology represents a promising trend for sensitive molecular analysis of etiologic agent with fast and simple operationalization. In addition to early genetic diagnosis, the biomolecular assay may help to monitor the progression of COVID-19 infection in a novel manner.
Fungi stand out as primary pathogens present in healthcare-acquired infections, presenting an increased number of cases even using appropriate antifungal therapy. Candida spp. is a predominant ...microorganism among several fungal pathogens present in the healthcare setting. Candidemia and candidiasis are fungal infections responsible for high morbidity and mortality among ill patients in hospitals. It is noticeable that prolonged hospital stays lead to a higher economic impact and increased risk for developing secondary fungal or even bacterial infections. New fast and sensitive approaches for the detection of Candida species is highly required. Electrochemical biosensors are an excellent alternative to conventional techniques by combining fast analyte detection, low cost, and the possibility of miniaturization. Lectins are carbohydrate-binding proteins with the capability to reach out to the microorganism cell wall. In this work, we proposed the development of an impedimetric biosensor for Candida spp. based on Concanavalin A (ConA) and wheat germ agglutinin (WGA) as recognition agents of the yeast cells. Atomic force microscopy images indicate changes in the biosensor surface after assembly of the molecules and exposure to fungal samples. Electrochemical impedance spectroscopy results revealed a proportional increase of charge transfer resistance (RCT) as fungal CFU increased, where four Candida species were evaluated (Candida krusei, Candida tropicalis, Candida parapsilosis and Candida albicans). The biosensor is useful to differentiate Candida spp. with a detection limit between 102 to 106 CFU mL−1. The obtained biosensor appears as an innovative candidate for the detection and differentiation of pathogenic Candida spp.
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•A new strategy to construct an electrochemical biosensor for Candida spp. has been achieved.•Two different lectin-based biosensors for selective discrimination of pathogenic Candida species were obtained.•ConA and WGA were able to detect and differentiate pathogenic Candida species.•We obtained sensors platforms with high sensitivity, selectivity and simple assembly process.
Systemic sclerosis (SSc) is a chronic, autoimmune disease that primarily affects connective tissue. SSc can be classified into limited cutaneous (lSSc) and diffuse cutaneous (dSSc). Oncostatin M ...receptor (sOSMR) is an important inflammatory biomarker expressed in the serum of patients with autoimmune diseases. A nanoengineered immunosensor surface was developed. The biosensor was composed of a conductive layer of polypyrrole, electrodeposited gold nanoparticles, and sOSMR protein for anti-human OSMR monoclonal antibody biorecognition. The electrochemical response evaluated by cyclic voltammetry and electrochemical impedance spectroscopy indicated the detection of the target analyte present in clinical samples from lSSc and dSSc patients. The voltammetric anodic shift for lSSc specimens was 82.7% ± 0.9–93.6% ± 3.2, and dSSc specimens was 118.7 ± 2.6 to 379.6 ± 2.6, revealing a differential diagnostic character for SSc subtypes. The sensor platform was adapted for identifying sOSMR, using anti-OSMR antibodies as bioreceptors. With a linear response range estimated from 0.005 to 500 pg mL−1 and a limit of detection of 0.42 pg mL−1, the sensing strategy demonstrated high sensitivity in identifying the human OSMR protein in clinical samples. The proposed biosensor is a promising and innovative tool for SSc-related biomarker research.
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•An innovative nanoimmunosensor applicable to systemic sclerosis was developed.•Flexible transducers were modified with polypyrrole films and gold nanoparticles.•Anti-OSMR antibodies and sOSMR protein were detected in clinical specimens.•Sclerosis diagnosis was correlated with diffuse and limited subtypes of the disease.•The sensor exhibited a limit of detection of 0.42 pg mL−1 with high selectivity.
The increasing number of multidrug resistance microorganisms is an alarming threat, and their rapid detection is essential to prevent nosocomial, foodborne, or waterborne infections. Many peptides ...derived from the venom of wasp Synoeca surinama have antimicrobial activity against Gram-positive and Gram-negative bacteria. Synoeca-MP, an antimicrobial peptide (AMP) from mastoparan family, seems to increase bacterial membrane permeability, promoting cytotoxicity and membrane disruption. Here Synoeca-MP was evaluated as biorecognition element tethered over chitosan-coated magnetic nanoparticles (Fe3O4-Chit). The transducing layer of the biosensor was developed from the self-assembling of 4-mercaptobenzoic acid (4-MBA) monolayer onto gold substrate. Atomic force microscopy (AFM) analyses confirmed the biointeraction between AMP and different pathogens membranes. The fabrication and performance of the biosensing assembly were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Detection of Enterococcus faecalis (G+), Klebsiella pneumoniae (G-), Pseudomonas aeruginosa (G-), and Candida tropicalis was assessed in a recognition range from 101 to 105 CFU.mL−1. An instrumental limit of detection of 10 CFU.mL−1 was obtained for each specimen. However, the device presented a preferential selectivity towards Gram-negative bacteria. The proposed biosensor is a sensitive, fast, and straightforward platform for microbial detection in aqueous samples, envisaged for environmental monitoring applications.
•A new electrochemical biosensor with high sensitivity towards Gram-negative species is presented.•The biosensor combines chitosan-coated magnetic nanoparticles with the antimicrobial peptide Synoeca-MP.•The sensor detected bacteria and fungi species with a LOD of 101 CFU mL−1.•The platform presented high sensitivity towards K. pneumoniae.•This biosensor stands out as a promising tool for fast microbial detection in liquid samples.
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•Lectin functionalized magnetic nanoparticles were able to detect microorganisms.•Au capping magnetic nanoparticles improved the electrochemical response.•The biosensor presented a ...limit of detection of 10 CFU mL−1.•Fe3O4@Au_ConA sensor differentiated bacteria species.
Biosensors are pre-prepared diagnostic devices composed of at least one biological probe. These devices are envisaged for the practical identification of specific targets of microbiological interest. In recent years, the use of narrow-specific probes such as lectins has been proven to distinguish bacteria and glycoproteins based on their superficial glycomic pattern. For instance, Concanavalin A is a carbohydrate-binding lectin indicated as a narrow-specific biological probe for Gram-negative bacteria. As a drawback, Gram-positive bacteria are frequently overlooked from lectin-based biosensing studies because their identification results in low resolution and overlapped signals. In this work, the authors explore the effect that platform nanostructuration has over the electrochemical response of ConA-based platforms constructed for bacterial detection; one is formed of chitosan-capped magnetic nanoparticles, and another is composed of gold nanoparticle-decorated magnetic nanoparticles. The biosensing platforms were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) as a function of bacterial concentration. Our results show that probe-target interaction causes variations in the electrical responses of nanostructured transducers. Moreover, the association of gold nanoparticles to magnetic nanoparticles resulted in an electrical enhancement capable of overcoming low resolution and overlapping Gram-positive identification. Both platforms attained a limit of detection of 10 ° CFU mL−1, which is useful for water analyses and sanitation concerns, where low CFU mL−1 are always expected. Although both platforms were able to detect Gram-negative bacteria, Gram-positives were only correctly differentiated by the gold nanoparticle-decorated magnetic nanoparticles, thus demonstrating the positive influence of hierarchically nanostructured platforms.
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•The biosensor can detect and differentiate among various Candida yeast species.•CLAVMO is a suitable biological probe that can be used to detect and differentiate Candida ...species.•Limits of detection (LODs) between 2 and 3 CFU mL-1 were obtained.
Yeast biotechnologies are a cornerstone to modern lifestyle in all spheres of society, as their products are essential for the economy and industrial activities. The life cycle of many yeasts such as Candida alternates between diplophase and haplophase. Both ploidies can exist as stable cultures; however, it has been shown that wild haploid yeast efficiently cross in poor environments, whereas wild diploid species hybridize predominantly in rich nutrient surroundings. Some Candida species have had their ploidy engineered to produce various important biomolecules useful to the detergent, food, pharmaceutical and other industries. Several works show that MALDI-TOF MS has become an ideal platform for ploidy analysis. Recent reports have shown that antimicrobial peptides (AMP) present enhanced hydrophobic interaction towards cell membranes. In this work, the authors explored a modified AMP named Clavanin A (CLAVMO) as an unprecedented bioreceptor capable of differentiating the molecular composition of the cell wall of Candida spp. A thin film of poly(3-thiophene acetic acid) (PTAA) was electropolymerized to avail the covalent immobilization of amino-functionalized titanium dioxide nanoparticles (TiO2NPs) whose electrochemical properties are excellent to provide a discernable redox response. Electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) were used to characterize the biosensor assembly and the biorecognition process. Additionally, MALDI-TOF was employed to confirm ploidy of Candida strains used in this work. Our results suggest that TiO2NPs_CLAVMO biosensor is a suitable biological probe that can be used to detect and differentiate Candida species based on their ploidy. For instance, C. Albicans and C. tropicalis, which are close related species known for being diploid presented higher impedimetric response than haploid species C.krusei and C. glabrata. The proposed biosensor stands out as a useful alternative for highly sensitive differentiation of Candida yeast cells, without the intricacies of MALDI-TOF sample preparation. The biodetection event and its electrochemical evaluation took less than 20 min to perform. The platform showed stability for over a week, a linear detection range between 101-106 CFU mL-1 and limits of detection (LODs) between 2 and 3 CFU mL-1.
The production of conductive and organic devices from a 3D printer represents a promising strategy for several areas. In particular, the synthesis of polypyrrole-coated acrylonitrile butadiene ...styrene (ABS) composites can be considered an important step to produce conductive supports for 3D printing. Herein, it is reported the production of ABS samples through the additive manufacturing process (3D printing) accordingly to the Fused Deposition Modeling (FDM) method. The hydrophilic behavior was controlled by the surface treatment using air plasma for the following step of coating with polypyrrole (PPy) via an in situ polymerization, using two different oxidants: ferric chloride (FeCl3.6H2O) and ammonium persulfate (APS). The chemical, optical, surface, and electrical properties of these materials were characterized through Fourier Transform infrared spectroscopy (FTIR), contact angle measurements, cyclic voltammetry, Scanning Electron Microscopy (SEM), 4-probe electrical measurement, and mechanical tensile testing. The ABS/PPy (FeCl3) composite exhibited a low electrical contact resistance and better performance for applications that require electrodes with a good conductance level.
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•We developed a biosensor platform based on an antigenic colloidal suspension as a biorecognition element.•The platform detects anti-cardiolipin (anti-C) antibodies in infected human ...serum.•The biosensor was able to detect the formation of immunocomplexes in serum samples.•We obtained a limit of detection of 1024 titer.
Syphilis is a sexually transmitted disease with high morbidity and mortality rates. Venereal disease research laboratory (VDRL) and rapid plasma reagin (RPR) testing are the most commonly used syphilis identification methods; however, both have low specificity. The available molecular assays are expensive and time-consuming. Electrochemical biosensors are an innovative approach for detecting multiple target analytes present in syphilis complex samples. In this work, we used a self-assembled monolayer (3-mercaptopropyl)trimethoxysilane (MPTS) to immobilize an antigenic colloidal suspension (containing cardiolipin, cholesterol, and lecithin) as a biorecognition element in a platform for detecting anti-cardiolipin (anti-C) antibodies in infected human serum. The biosensor platform was evaluated through cyclic voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy. Microscopic evaluation revealed the formation of small cardiolipin-anti-C complexes at the maximum titer of 1:32, thus indicating the serum’s syphilis infection positivity. Anti-C antibody detection was evaluated by blocking electron current and oxidation–reduction processes at the electrode–electrolyte interface. The proposed sensor yielded a linear response (serum dilutions ranging from 1:8 to 1:1024 titer) with a regression coefficient of 0.97. We obtained a limit of detection of 1:1024 titer and high selectivity against interfering biomolecules. The developed biosensor may provide a promising alternative for syphilis diagnosis and follow-up treatment.
The distribution of selected aromatic compounds and microbiology were assessed in superficial sediments from Suruí Mangrove, Guanabara Bay. Samples were collected at 23 stations, and particle size, ...organic matter, aromatic compounds, microbiology activity, biopolymers, and topography were determined. The concentration of aromatic compounds was distributed in patches over the entire mangrove, and their highest total concentration was determinated in the mangrove's central area. Particle size differed from most mangroves in that Suruí Mangrove has chernies on the edges and in front of the mangrove, and sand across the whole surface, which hampers the relationship between particle size and hydrocarbons. An average @ 10% p/p of organic matter was obtained, and biopolymers presented high concentrations, especially in the central and back areas of the mangrove. The biopolymers were distributed in high concentrations. The presence of fine sediments is an important factor in hydrocarbon accumulation. With high concentration of organic matter and biopolymers, and the topography with chernies and roots protecting the mangrove, calmer areas are created with the deposition of material transported by wave action. Compared to global distributions, concentrations of aromatic compounds in Suruí Mangrove may be classified from moderate to high, showing that the studied area is highly impacted.
A distribuição de compostos aromáticos selecionados e a microbiologia foram avaliados em sedimentos superficiais do Manguezal de Suruí, Baía de Guanabara. Amostras foram coletadas em 23 pontos e determinados a granulometria, matéria orgânica, compostos aromáticos, atividade microbiológica, biopolímeros e a topografia. A concentração dos compostos aromáticos foi distribuída em manchas por todo o manguezal e sua concentração total mais elevada foi encontrada na área central do manguezal. A granulometria diferiu da maioria dos manguezais, uma vez que no Manguezal de Suruí existem chernies nas bordas e na frente dos manguezais e areia através da superfície inteira, impedindo o relacionamento entre granulometria e os hidrocarbonetos. Uma média de 10% p/p da matéria orgânica foi obtida e os biopolímeros apresentaram concentrações elevadas, especialmente na área central e fundo do Manguezal. Os biopolímeros se distribuíram em altas concentrações. A presença de finos sedimentos é fator importante na acumulação de hidrocarbonetos. Na concentração elevada de matéria orgânica e de biopolímeros, topografia com chernies e as raízes que protegem os manguezais, áreas mais calmas são criadas, com depósito do material transportado pela ação das ondas. Comparadas às distribuições globais, as concentrações das substâncias aromáticas neste manguezal podem ser classificadas de moderadas a elevadas, demonstrando que a área estudada está altamente impactada.
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