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The guarantee of food safety requires fast and accurate control for all contaminants, chemicals and bacteria, which are harmful to human health. Ensuring the safety and quality of food is the main interest both for the food industry and for consumers. In the food industry, the safety of a food product is evaluated through chemical and microbiological analysis: these procedures conventionally use the technique as chromatography, spectrophotometry and electrophoresis that are time-consuming, require highly trained personnel, are expensive and require steps of sample pretreatment, increasing the time of analysis. Consequently, among food and beverage industries, exists a growing demand in biosensing technologies as simple, rapid, accurate, low – cost and portable analytical devices for the monitoring and detection of chemical and microbiological contaminants (toxins, mycotoxins, pathogenic bacteria, pesticides and allergens) that endanger the food safety. Among biosensors, the label-free biosensors, characterised by direct detection of the analyte of interest, exploiting the advantages of an impedimetric transduction technique, seem to be the most promising devices for the future. In the last years, the potential use of Electrochemical Impedance Spectroscopy technique has been widely considered in the biosensor field; it is, in fact, a powerful, non-destructive and informative technique which can be used to study the electrical properties of the sensing device interface and to trace the reactions that occur on it. For these reasons, the application of impedimetric technique as a transduction technology has allowed the label-free detection and sensitive quantification of the bio interaction in different application and thus for the development of food hazards biosensors too. This review provides the current situation in the literature on label-free impedimetric biosensors in food safety. [ABSTRACT FROM AUTHOR]

In this work, the development of an impedimetric label-free immunosensor for the detection of Escherichia coli O157:H7 is reported. Different immobilization techniques of monoclonal anti-E. coli were tested, in order to reach the very low limit of detections. The comparison between the immobilization procedures underlined the advantages of the oriented procedure and the use of a dendrimer, which allowed for immobilizing a higher number of antibody units, reaching a very high sensitivity. However, the use of activated ferrocene as electron-transferring mediator, which improved the electrical properties of the system, resulted in a very low limit of detection equal to 3 cfu/mL. This immunosensor was used to analyze milk and meat samples obtaining a good agreement with the results of the ELISA methods. [ABSTRACT FROM AUTHOR]

Several illnesses that are chronic and acute are becoming more relevant as the world's aging population expands, and the medical sector is transforming rapidly, as a consequence of which the need for "point-of-care" (POC), identification/detection, and real time management of health issues that have been required for a long time are increasing. Biomarkers are biological markers that help to detect status of health or disease. Biosensors' applications are for screening for early detection, chronic disease treatment, health management, and well-being surveillance. Smart devices that allow continual monitoring of vital biomarkers for physiological health monitoring, medical diagnosis, and assessment are becoming increasingly widespread in a variety of applications, ranging from biomedical to healthcare systems of surveillance and monitoring. The term "smart" is used due to the ability of these devices to extract data with intelligence and in real time. Wearable, implantable, ingestible, and portable devices can all be considered smart devices; this is due to their ability of smart interpretation of data, through their smart sensors or biosensors and indicators. Wearable and portable devices have progressed more and more in the shape of various accessories, integrated clothes, and body attachments and inserts. Moreover, implantable and ingestible devices allow for the medical diagnosis and treatment of patients using tiny sensors and biomedical gadgets or devices have become available, thus increasing the quality and efficacy of medical treatments by a significant margin. This article summarizes the state of the art in portable, wearable, ingestible, and implantable devices for health status monitoring and disease management and their possible applications. It also identifies some new technologies that have the potential to contribute to the development of personalized care. Further, these devices are non-invasive in nature, providing information with accuracy and in given time, thus making these devices important for the future use of humanity. [ABSTRACT FROM AUTHOR]

• An impedimetric biosensor for Salmonella spp. detection was developed. • Nisin was used for detection of different Gram-positive and Gram-negative bacteria. • The proposed biosensor is able to detect selectively Salmonella cells. • The biosensor show a Limit of Detection for Salmonella of 150 CFU/ml. Nisin is an antimicrobial peptide with bacterial, fungicidal, virucidal properties, attacking bacteria and destroying the cell membranes. Thanks to its stability to hard conditions, it is a candidate for the use as molecular recognition elements in biosensing platform. In this work, the use of nisin as a biological molecule for the development of a sensitive biosensor for bacteria detection is reported: nisin molecules were immobilised on gold electrodes and Electrochemical Impedance Spectroscopy was to investigate the electrochemical responses after the exposure of the biosensor to different bacteria. The biosensor was able to detect all bacterium tested with different impedimetric responses; the singular impedimetric behaviours recorded after the exposure to pathogenic and non – pathogenic Salmonella strains, highlighted the possibility of the proposed biosensor to detect selectively Salmonella cells with a low limit of detection of 1.5 * 101 CFU/mL. Finally, the developed biosensor was used to detect Salmonella in milk. [ABSTRACT FROM AUTHOR]

Introduces a series of articles on biochemical analysis.

There is currently a lot of interest in the construction of point-of-care devices stemming from paper-based origami biosensors. These devices demonstrate how paper's foldability permits the construction of sensitive, selective, user-friendly, intelligent, and maintainable analytical devices for the detection of several ailments. Herein, the first example of the electrochemical aptasensor-based polyvalent dengue viral antigen detection using the origami paper-folding method is presented. Coupling it with an aptamer leads to the development of a new notation known as OBAs, or origami-based aptasensor, that presents a multitude of advantages to the developed platform, such as assisting in safeguarding the sample from air-dust particles, providing confidentiality, and providing a closed chamber to the electrodes. In this paper, gold-decorated nanocomposites of zinc and graphene oxide (Au/ZnO/GO) were synthesized via the chemical method, and characterization was conducted by Scanning Electron Microscope, Transmission Electron Microscope, UV-Vis, and XRD which reveals the successful formation of nanocomposites, mainly helping to enhance the signal and specificity of the sensor by employing aptamers, since isolation and purification procedures are not required. The biosensor that is being demonstrated here is affordable, simple, and efficient. The reported biosensor is an OBA detection of polyvalent antigens of the dengue virus in human serum, presenting a good range from 0.0001 to 0.1 mg/mL with a limit of detection of 0.0001 mg/mL. The reported single-folding ori-aptasensor demonstrates exceptional sensitivity, specificity, and performance in human serum assays, and can also be used for the POC testing of various viral infections in remote areas and underdeveloped countries, as well as being potentially effective during outbreaks. Highlights: (1) First report on origami-based aptasensors for the detection of polyvalent antigens of DENV; (2) In-house construction of low-cost origami-based setup; (3) Gold-decorated zinc/graphene nanocomposite characterization was confirmed via FESEM/UV-Vis/FTIR; (4) Cross-reactivity of dengue-aptamer has been deduced; (5) Electrochemical validation was conducted through CV. [ABSTRACT FROM AUTHOR]

Foodborne illness is posing major health problems among all world population. Among all pathogens, bacteria are causing more severe infections in food samples. Listeria monocytogenes is most lethal foodborne illness in human, causing approximately 1600 people infected and 260 deaths each year in the USA. In this review, numerous strategies of detection are presented together with discussions about their pros and cons. The primary emphasis has been done on electrochemical detection methods for L.monocytogenes. More than hundred research papers have been critically studied to elucidate the impact of L.monocytogenes on mortality and global socio-economic development. The literature study proves that electrochemical approach is the best among all traditional methods and using aptamers as biological recognition elements offer more advanced features to the diagnosis. Studies concluded that apta-sensors increase the sensitivity and specificity of L.monocytogenes detection. [ABSTRACT FROM AUTHOR]

We present the development of an electrochemical paper-based analytical device (ePAD) for the detection of methamphetamine. Methamphetamine is a stimulant that young people use as an addictive narcotic, and it must be detected quickly since it may be hazardous. The suggested ePAD has the advantages of being simple, affordable, and recyclable. This ePAD was developed by immobilizing a methamphetamine-binding aptamer onto Ag-ZnO nanocomposite electrodes. The Ag-ZnO nanocomposites were synthesized via a chemical method and were further characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, and UV-vis spectrometry in terms of their size, shape, and colloidal activity. The developed sensor showed a limit of detection of about 0.1 μg/mL, with an optimum response time of about 25 s, and its extensive linear range was between 0.01 and 6 μg/mL. The application of the sensor was recognized by spiking different beverages with methamphetamine. The developed sensor has a shelf life of about 30 days. This cost-effective and portable platform might prove to be highly successful in forensic diagnostic applications and will benefit those who cannot afford expensive medical tests. [ABSTRACT FROM AUTHOR]

Due to their increasing use in agriculture, the presence of pesticide residues in food and water currently represents one of the major issues for the food safety. Among the pesticides, organophosphate and carbamate species are the most used, and their toxicity is mainly due to their inhibitory effect on acetylcholinesterase (AChE). For this reason, a monoenzymatic acetylcholinesterase impedimetric biosensor was developed in order to sensitively detect carbamate and organophosphate compounds with a very fast response. The working principle of the AChE biosensor exploits the capability of carbamate and organophosphate pesticides to form a stable complex with the enzyme, which causes an impedimetric change. The impedimetric biosensor showed a linearity between 5 and 170 ppb for carbamates and 2.5-170 ppb for organophosphate compounds, with a reproducibility (RSD%) interelectrode equal to 4.8 and 3.1% for organophosphates and carbamates, respectively. Moreover, the common amperometric evaluation of AChE inhibition degree was correlated to the impedimetric changes of the electrode surface, showing a good correlation ( R = 0.99 for carbamates and R = 0.98 for organophosphates) between the two methods. In contrast to amperometric evaluation that needs a response time of 20 min, impedimetric detection requires only 4 min. Finally, the impedimetric biosensor was used to measure carbaryl and dichlorvos spiked in different concentrations in tap water and lettuce samples, showing a recovery near to 100% for all concentrations and for both pesticides. [ABSTRACT FROM AUTHOR]

Celiac disease is a serious autoimmune disorder caused by the ingestion of gluten. Gliadin is the gluten fraction responsible for the triggering of disease. The only cure for the celiac patients, known until now, is a diet with gluten-free foods, classified by the European regulation doesn't exceed 20 ppm in gluten. With the aim to guarantee the food safety for celiac patients in this study the developing and optimization of a fast and reliable label free impedimetric aptasensor for gliadin detection is reported. The aptamer (Gli1) at 0.5 μmol and poly (amidoamine) dendrimer of fourth generation (PAMAM G4) at 2 mg/ml were chosen during the developing steps of the sensing platform because the best ones for the detection of low gluten concentrations with the highest sensitivity. The aptasensor showed linearity in the range of 5–50 μg/l and 50–1000 μg/l in gliadin, a limit of detection of 5 μg/l corresponding to 5 ppm of gluten, a reproducibility lower than 5% and a storage stability at 4 °C of two months. Finally the aptasensor was used to measure gluten, in gluten and gluten-free food products, showing a good agreement with the results obtained with official R5 ELISA method. [ABSTRACT FROM AUTHOR]

In this work the development and optimization of an impedimetric label free immunosensor for the detection of Ochratoxin A (OTA) is reported. Two antibody immobilization methods (oriented and not oriented) were compared highlighting a lower limit of detection (5 pg/ml) for the not oriented immobilization but a closer linear range in contrast to oriented anti-OTA immunosensors which showed linearity in the range of 0.01–5 ng/mL OTA. The analysis of the Atomic Force Microscopy (AFM) images showed two different nanostructures indicating that the use of oriented immobilization created a more ordered and highly dense antibody surface. Finally the oriented immunosensor was used to quantify OTA in spiked cocoa bean samples and the results were compared with those registered with competitive ELISA kit. The immunosensor was sensitive to OTA lower than 2 μg/kg that represents the lower acceptable limit of OTA established by European legislation for the common food products. [ABSTRACT FROM AUTHOR]

Thick film electrode based biosensors containing Trametes versicolor (TvL) and Aspergillus niger (AnL) laccases and Agaricus bisporus tissues (AbT) were developed for the determination of phenolic compounds and the measurement was based on oxygen consumption in relation to analyte oxidation. The electrodeposited organic polymer; polyaniline was used as a matrix for the immobilization in the preparation of thick film sensors. The systems were calibrated for different phenolic substances. A linearity was obtained in concentration range between 0.4 and 6.0 μM phenol, 0.2 and 1.0 μM catechol, 2.0 and 20.0 μM l-DOPA for TvL based biosensor; for AnL based enzyme electrode 0.4 and 4.0 μM phenol, 0.4 and 15 μM catechol, 0.4 and 6.0 μM l-DOPA; for AbT electrode 1.0 and 10 μM phenol, 0.4 and 1.6 μM catechol, 1.0 and 10 μM l-DOPA, respectively, in the response time of 300 s. Furthermore, as well as sample application and accuracy, optimum pH, temperature and thermal stabilities of the proposed systems were also detected. [Copyright &y& Elsevier]

Amperometric biosensors using bacterial cells were developed for the determination of phenolic compounds and the measurement was based on the respiratory activity of the cells. For this purpose, Pseudomonas putida DSM 50026 which is one of the well-known phenol degrading organisms, was used as a biological component. The cells were grown in the presence of phenol as the sole source of organic carbon. As well as phenol adapted cells, the bacterium which used the glucose as the major carbon source, was also used to obtain another type of biosensor for the comparison of the responses and specificities towards different xenobiotics. The commercial oxygen electrode was used as a transducer to test the sensor responses for both induced and non-induced cells. Our results showed that the adaptation step enable us to obtain biosensor devices with different substrate specificity. Moreover, P. putida was immobilized on the surface of thick film working electrodes made of gold by using gelatin membrane cross-linked with glutaraldehyde. The biosensors were calibrated for different phenolic substances. Furthermore, phenol detection was performed in synthetic wastewater samples. [Copyright &y& Elsevier]

Early identification of ovarian cancer improves treatment options & survival rates. An electrochemical paper analytical device (ePAD) was reported in this study for detecting Platelet-derived growth factor (PDGF), an ovarian cancer biomarker. This research aims to create a quick nano-biosensing approach to recognize deadly ovarian cancer (OC) at an initial phase. The suggested ePAD has numerous positive characteristics, including simple, low-cost, repeatable, & disposable. The ePAD's working electrode contains silver nanoparticles. Furthermore, aptamers have improved the biosensor's functionality. Transmission electron microscopy (TEM), FTIR analysis, X-ray diffraction (XRD), UV–vis spectroscopy, & Zeta potential test were utilized to evaluate the silver nanoparticles' morphological, optical, elemental content, and phase analyses. This aptamer-modified ePAD helps amplify the designed platform's signal to detect PDGF. The interaction of aptamer & PDGF was discovered by lowering the current created by the contact with methylene blue (MB), an anionic indicator. The designed sensor demonstrated an optimum response & broad linearity of 0.01–10.0 μg/ml for PDGF, with 0.01 μg/ml of limit of detection (LOD). [Display omitted] • The developed sensor showed good sensitivity as well as reproducibility. • A chemically synthesized and very well characterized silver-based nanoparticles were utilized. • Cross-reactivity was confirmed by utilizing Urea. • The constructed electrochemical sensor worked efficiently in artificial serum. • This sensor could be used for detecting ovarian cancer biomarker. [ABSTRACT FROM AUTHOR]

In winemaking gluconic acid is an important marker for quantitative evaluation of grape infection by Botrytis cinerea. A screen-printed amperometric bienzymatic sensor for the determination of gluconic acid based on gluconate kinase (GK) and 6-phospho-D-gluconate dehydrogenase (6PGDH) coimmobilized onto polyaniline/poly (2-acrylamido-2-methyl-1-propanesulfonic acid; PANI-PAAMPSA) is reported in this study. The conductive polymer electrodeposed on the working electrode surface allowed the detection of NADH at low potential (0.1 V) with a linear range from 4 x 10-3 to 1 mM (R² = 0.99) and a sensitivity of 419.44 nA⋅mM-1. The bienzymatic sensor has been optimized with regard to GK/6PGDH enzymatic unit ratio and ATP/NADP+ molar ratio which resulted equal to 0.33 and 1.2, respectively. Under these conditions a sensitivity of 255.2 nA⋅mM-1, a limit of detection of 5 µM and a Relative Standard Deviation (RSD) of 4.2% (n = 5) have been observed. Finally, the biosensor has been applied for gluconic acid measurements in must grape samples and the matrix effect has been taken into consideration. The results have been compared with those obtained on the same samples with a commercial kit based on a spectrophotometric enzyme assay and were in good agreement, showing the capability of the bienzymatic PANI-PAAMPSA biosensor for gluconic acid measurements and thus for the evaluation of Botrytis cinerea infection in grapes. [ABSTRACT FROM AUTHOR]

Amperometric biosensors using laccase from Trametes versicolor as a bioelement were developed for 2,4-dichloro phenoxy acetic acid (2,4-D). Laccase enzyme was immobilized by gelatin and glutaraldehyde onto a Clark oxygen probe and screen printed electrodes (SPEs). Amperometric and chronoamperometric measurements were carried out with the biosensors. First, the effect of laccase activity on the biosensor performances was investigated for both biosensors, and then optimum pH and temperature and also thermal stability of the biosensors were tested. In addition, the detection ranges of some phenolic compounds were obtained by the help of calibration graphs of them. In repeatability studies, variation coefficients and standard deviations for both biosensors were also calculated by the studies done for this purposes. Finally, the biosensors were applied to the determination of 2,4-D in a real herbicide sample. [ABSTRACT FROM AUTHOR]

The functional tests of a previously obtained continuous flow micro-cell revealed a rather low value of the sensitivity of the chronoamperometric measurements as well as a poor reliability of both fluidic and electric connections. The engineering of the micro-cell regards the improvement of the following characteristics: (1) integrating the reference electrode on the chip, (2) designing a specific pattern of the electrodes and (3) serially distributing them along the pipeline reservoir. Thus, a plug-flow device is obtained and the preliminary tests confirm its functionality together with an improved sensitivity. The use of photosensitive glass (Foturan®) for obtaining the reservoir and its vertical openings allowed an improvement of the transversal shape and thus of the fluid flow. Better connections are achieved by the development of more reliable and rigid glass fluidic connections as well as of flexible elastomer-based solderless electric connections combined with both a standard DIL40 socket and standard flat cable connectors. [ABSTRACT FROM AUTHOR]

Amperometric biosensors using Pseudomonas putida cells as a bioelement were developed for 2,4-dichloro phenoxy acetic acid (2,4-D). After the adaptation process of Pseudomonas putida to 2,4-D, cells were immobilized onto the screen printed graphite electrodes (SPG) as well as Clark oxygen probe by gelatin and glutaraldehyde. Optimum pH, temperature, and stability of the biosensor were investigated. Substrate specificities for various phenolic compounds were also searched. In repeatability studies, variation coefficients and standard deviations for both type of systems were calculated; SPG and Clark electrodes were calculated and results are given as a comparison of two systems. Finally, the biosensors were applied to 2,4-D determination in a real herbicide sample. [ABSTRACT FROM AUTHOR]

Organophosphorous (OP) insecticides reveal acute toxicity because of their capability to affect the nervous system through the inhibition of acetyl cholinesterase function in regulating the neurotransmitter acetylcholine. The present work shows an example of an easy to be handled inhibition electrochemical biosensor, based on thick film technology for low cost production of screen printed electrodes. Anti-cholinesterase activity in specific fruits was determined measuring the inhibition of acetyl cholinesterase enzyme owing to the presence of OP pesticides. Paraoxon was taken as reference pesticide for each measurement. The main fluidic critical parameters were investigated under flow injection analysis, through the comparison of different enzymatic immobilisation methods. Analytical features were evaluated as a function of experimental parameters. The analytical detection was developed in a three step procedure and the pesticides content was measured in strawberries samples taken from the local market. The separation between the acetyl cholinesterase inhibition and the electrochemical detection with the choline oxidase biosensor decreases the total analysis time, allowing improvements in reproducibility and stability of the system. A comparison with reference materials and standard analytical procedures for pesticides will be required in the future for evaluating the reliability of the method. [ABSTRACT FROM AUTHOR]

Gold nanowires were synthesized within polycarbonate membranes according to an electroless deposition method, obtaining nanoelectrode ensembles (NEEs) with special electrochemical features. NEEs were coupled with home-produced carbon graphite screen printed electrodes and the electrochemical properties of the original nanoelectrode ensemble on screen printed substrate (NEE/SPS) assembly has been tested for sensors application. Glucose oxidase has been used as model enzyme in order to verify the feasibility of disposable gold NEE/SPS biosensors. Finally, different immobilisation and electrochemical deposition techniques based on either self assembled monolayers of cysteamine (CYS) or amino-propyl-triethoxysilane (APTES) and conductive polyaniline (PANI) molecular wires were used. Spatial patterning of the enzyme on the polycarbonate surface and of PANI wires on gold nanoelectrodes was obtained. Possible direct electron transfer between the enzyme and the PANI modified gold nanoelectrodes has been evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Two biosensors based on Trametes versicolor laccase (TvL) were developed for the determination of phenolic compounds. Commercial oxygen electrode and ferrocene-modified screen-printed graphite electrodes were used for preparation of laccase biosensors. The systems were calibrated for three phenolic acids. Linearity was obtained in the concentration range 0.1–1.0μM caffeic acid, 0.05–0.2μM ferulic acid, 2.0–14.0μM syringic acid for laccase immobilised on a commercial oxygen electrode and 2.0–30.0μM caffeic acid, 2.0–10.0μM ferulic acid, 4.0–30.0μM syringic acid for laccase immobilised on ferrocene-modified screen-printed electrodes. Furthermore, optimal pH, temperature and thermal stability studies were performed with the commercial oxygen electrode. Both electrodes were used for determination of a class of phenolic acids, achieving a cheap and fast tool and an easy to be used procedure for screening real samples of human plasma. [Copyright &y& Elsevier]

A biosensor was developed by immobilizing laccase onto mercury thin film electrode (MTFE) by means of gelatin that is then crosslinked with glutaraldehyde. Mercury thin film (MTF) was deposited onto glassy carbon electrode (GCE) and the obtained biosensor was utilized for the determination of phenolic compounds. The measurement was based on the amperometric detection of oxygen consumption in relation to analyte oxidation. The optimum experimental conditions for the biosensor were investigated and the system was calibrated for both catechol and phenol. A linear relationship between sensor responses and analyte concentrations was obtained in concentration range between 0.5 × 10 -6 – 5.0 × 10 -6 M for catechol and 2.5 × 10 -6 – 2.0 × 10 -6 M for phenol, respectively. Mercury thin film was also formed onto the surface of screen printed graphite electrodes and applied for the catechol detection. The linearity was observed in concentration range between 2.5 × 10 -6 – 3.0 × 10 -5 M. [ABSTRACT FROM AUTHOR]

A disposable tyrosinase biosensor has been developed for the analysis of phenols and polyphenols, by modifying screen printed electrodes (SPEs) with addition of suitable mediators of redox processes directly into the conductive pastes. The percent ratio of mediator in the pastes was chosen depending on the electrochemical sensitivity either in batch or standard flow conditions. Ferrocene modified carbon electrodes have been used on whose surface the enzyme tyrosinase was immobilized in a glutaraldehyde cross-linked matrix of bovine serum albumin. Mixing the mediator to the electrode pastes should overcome transport limitations, due to its dissolution, which occur in commonly used immobilization procedures. Different immobilization techniques of tyrosinase on SPEs in the detection of phenolic compounds were tested and compared. Modified SPEs showed relatively good reproducibility and detection limits in the micromolar range for all phenolic compounds used. Major sensor parameters have been optimized in flow systems putting special attention on operating potential, pH and buffer composition, which strongly affect the detection of polyphenols and operational stability in wine. The resulting biosensors were stored and dried for a minimum of 8  h at 4°C, and showed a shelf stability of about 30 days. The procedure has been applied both on a synthetic wine matrix and on real samples, to determine the ‘pool’ of phenolic composition in terms of phenol concentration. [ABSTRACT FROM AUTHOR]

Abstract: This article presents a bioelectrochemical system for the determination of pesticides by enzyme inhibition data. Measurements are performed by electrochemically monitoring the inhibition of the catalytic activity of the enzyme alkaline phosphatase (ALP) either in the presence or in the absence of pesticides, and particularly of Malathion and of 2,4-dichlorophenoxyacetic acid (2,4-D), representatives of the general classes of organophosphorous and organochlorinated agents. ALP catalytic activity was determined by using two different analytical configurations: (a) an amperometric ALP based biosensors using 3-indoxyl phosphate as the enzyme substrate; (b) a system allowing the voltammetric determination of the electroactive products of the ALP catalyzed reactions by using two different substrates: phenyl phosphate (PP) and ascorbate-2-phosphate (A-2-P). Studies of cyclic voltammetry and amperometry were performed first to define the optimal experimental conditions of the electrochemical measurements. For the optimal experimental conditions (Tris–0.1 M HCl aqueous buffer solution at pH 8.0, incubation time of 30–60 min) a detection limit of 0.5–6 μgl−1 is obtained, with a response, which is linear over 1–2 decades of concentration. [Copyright &y& Elsevier]

A microbial biosensor was developed for the determination of phenolic compounds and the measurement was based on oxygen consumption in relation to analyte oxidation. Induced cells of Pseudomonas putida DSM 50026 were immobilised on the surface of SPG electrodes covered with cellulose acetate membrane by means of gelatine which was then cross linked with glutaraldehyde. The systems were calibrated for different phenolic substances. Detection ranges were 0.1–1.0 μM for phenol and 0.05–1.0 μM for l-tyrosine and l-DOPA, respectively, with a response time of 3 min. Furthermore, phenol detection was performed in the presence of synthetic wastewater samples. [Copyright &y& Elsevier]

• Nucleic acid-based detection of Covid-19 is discussed. • Biosensors as the point-of-care diagnostic methods are summarised. • A comparative discussion is made on Covid-19 biosensors using different techniques. • Future trends for COVID-19 detection was described. The recent outbreak of COVID-19 has created much inconvenience and fear that the virus can seriously affect humans, causing health hazards and death. This pandemic has created much worry and as per the report by World Health Organization (WHO), more than 43 million individuals in 215 countries and territories were affected. People around the world are still struggling to overcome the problems associated with this pandemic. Of all the available methods, reverse-transcriptase polymerase chain reaction (RT-PCR) has been widely practiced for the pandemic detection even though several diagnostic tools are available having varying accuracy and sensitivity. The method offers many advantages making it a life-saving tool, but the method has the limitation of transporting to the nearest pathology lab, thus limiting its application in resource limited settings. This has a risen a crucial need for point-of-care devices for on-site detection. In this venture, biosensors have been used, since they can be applied immediately at the point-of-care. This review will discuss about the available diagnostic methods and biosensors for COVID-19 detection. [ABSTRACT FROM AUTHOR]

Hepatitis A (HA) is an acute human infectious disease caused by a positive single-stranded RNA virus (HAV). It is mainly acquired through the fecal–oral route and is primarily spread by contact between people and exposure to contaminated water and food. Recently, large outbreaks of HA have been reported by low and moderate endemicity countries, emphasizing its importance in public health and the need for rapid and large-scale diagnostic tests to support public health decisions on HA. This work proposes a new tool for HAV diagnosis based on the association of surface plasmonic resonance with major capsid protein VP1 (SPR-HAVP1 assay), detecting IgM antibodies for HAV in human serum samples. Structural analyses of VP1 B-lymphocyte epitopes showed continuous and discontinuous epitopes. The discontinuous epitopes were identified in the N-terminal region of the VP1 protein. Both epitope types in the VP1 protein were shown by the reactivity of VP1 in native and denaturing conditions to IgM anti-HAV, which was favorable to tests of VP1 in the SPR assays. SPR-HAVP1 assays showed good performance in the detection of IgM polyclonal antibody anti-HAV. These assays were performed using a COOH5 sensor chip functionalized with VP1 protein. The sensorgram record showed a significant difference between positive and negative serum samples, which was confirmed by analysis of variation of initial and final dissociation values through time (ΔRUd/t). The data gathered here are unequivocal evidence that the SPR-HAVP1 strategy can be applied to detect IgM antibodies in human serum positive to the HAV. This is a new tool to be explored to diagnose human HAV infections. [ABSTRACT FROM AUTHOR]

We have developed a membrane filter-assisted cell-based biosensing platform by using a polyester membrane as a three-dimensional (3D) cell culture scaffold in which cells can be grown by physical attachment. The membrane was simply treated with ethanol to increase surficial hydrophobicity, inducing the stable settlement of cells via gravity. The 3D membrane scaffold was able to provide a relatively longer cell incubation time (up to 16 days) as compared to a common two-dimensional (2D) cell culture environment. For a practical application, we fabricated a cylindrical cartridge to support the scaffold membranes stacked inside the cartridge, enabling not only the maintenance of a certain volume of culture media but also the simple exchange of media in a flow-through manner. The cartridge-type cell-based analytical system was exemplified for pathogen detection by measuring the quantities of toll-like receptor 1 (TLR1) induced by applying a lysate of P. aeruginosa and live E. coli, respectively, providing a fast, convenient colorimetric TLR1 immunoassay. The color images of membranes were digitized to obtain the response signals. We expect the method to further be applied as an alternative tool to animal testing in various research areas such as cosmetic toxicity and drug efficiency. [ABSTRACT FROM AUTHOR]

Norovirus is one of the leading causes of gastroenteritis, acute vomiting, intense diarrhoea, acute pain in the stomach, high fever, headaches, and body pain. Conventional methods of detection gave us very promising results but had disadvantages such as low sensitivity, cost ineffectiveness, reduced specificity and selectivity, etc. Therefore, biosensors can be a viable alternative device which can overcome all setbacks associated with the conventional method. An electrochemical sensor based on oxidized graphitic carbon nitride (Ox-g-C3N4) modified electrochemical paper-based analytical device (ePAD) was fabricated for the detection of norovirus DNA. The synthesized Ox-g-C3N4 nanosheets were characterized by field emission scanning electron microscopy (FESEM), X-ray Diffraction (XRD), UV-Vis spectroscopy and X-Ray Photoelectron Spectroscopy. The capture probe DNA (PDNA) modified electrodes were characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). These two characterization techniques were also employed to find the optimal scan rate, response time and temperature of the fabricated sensor. The fabricated biosensor showed a limit of detection (LOD) of 100 fM. Furthermore, the specificity of the reported biosensor was affirmed by testing the response of capture probe DNA with oxidized graphitic carbon nitride (PDNA/Ox-g-C3N4) modified ePAD on the introduction of a non-complimentary DNA. The fabricated ePAD sensor is easy to fabricate, cost effective and specific, and requires a minimum analysis time of 5 s. [ABSTRACT FROM AUTHOR]