Screen-printed electrodes for biosensing: a review (2008–2013)

Recent advances in screen-printed carbon electrodes for food additive analysis

Screen-printed carbon electrodes (SPCEs) are regarded as the actual and future sensing option for additive analysis in food samples; nonetheless, the sample preparation, selectivity, and detectability are key challenges to overcome for its technological development and wide application. In the present review, we inform, discuss, and compare some pivotal aspects associated with the fabrication of SPCEs, the presence of additives in foods, sample preparation, and voltammetric measurements of additives in food samples. Also, the proposed study has indicated that it is possible to develop suitable options for electroanalytical methodologies by using bare or modified SPCEs, which present affordable results in terms of selectivity, linear concentration range, and limit of detection for different classes of additives. Lastly, the review introduces challenging points that can be carefully evaluated for the next generation of SPCEs dedicated to additive analysis.

A life cycle assessment approach to minimize environmental impact for sustainable printed sensors

A printed hybrid sensor tag for applications in disposable healthcare and environmental monitoring optimized toward sustainability is presented. Following a systematic Life Cycle Assessment according to ISO 14040:2006 guidelines, the global warming potential associated with various substrate-, electrode-, and sensing materials, as well as manufacturing and end-of-life strategies, are evaluated. Results show that the utilization of bio-based polyethylene and copper inks can minimize the global warming potential most effectively by up to 39% from 42gCO2eq to 25.7gCO2eq per sensor tag. Among manufacturing methods, screen printing coupled with intense pulse light curing emerges as the most eco-efficient combination. Recycling is the most sustainable end-of-life option, although infrastructure challenges impede its full implementation. The silicon sensor chip needed for data communication has been identified as environmental hotspot. This study offers a comprehensive environmental evaluation of sustainable printed sensors and highlights critical challenges and opportunities for the electronics industry, particularly in relation to material selection, recycling strategies, and system-level considerations.

Immunoelectrochemical assessment of human IgE in non-invasive samples of allergic individuals using PdNCs-labelled antibodies

The escalating global prevalence of allergies presents a substantial public health challenge. Immunoglobulin E (IgE) serves as a key biomarker for allergic diseases, often measured in blood serum by ELISA immunoassays. Despite recent interest in minimally invasive sampling of biological fluids, the low sample volumes and IgE concentrations demand highly sensitive methodologies, typically confined to centralized laboratories. In this article, a decentralizable approach based on competitive immunoassays using Pd nanocluster (PdNCs)-labelled antibodies for electrochemical detection is proposed. With this aim, PdNCs were successfully bioconjugated with an anti-hIgE antibody to perform competitive immunoassays. To improve the analytical capabilities of the methodology, disposable screen-printed carbon electrodes with dual working electrodes were used for enhancing precision. Prior electrodeposition of PdNCs at - 0.6 V for 90 s significantly improved sensitivity (7.1 µA g ng⁻1) and lowered the limit of detection (LoD) to 0.3 ng g⁻1 for PdNCs determination. The use of PdNCs as labels resulted in an improvement in the LoD for IgE determination. Calibration curves performed using competitive immunoassays for IgE determination, ranging from 10-5 to 102 ng g-1, demonstrated sensitivity comparable to high-tech methods, with a LoD of 0.008 ng g-1 for electrochemical measurements. Bimodal detection of Pd (linear sweep voltammetry and inductively coupled plasma-mass spectrometry) in various biological fluids (saliva, tears, nasal exudate, capillary blood, and blood serum) revealed significant differences in IgE levels between allergic and non-allergic individuals. Notably, capillary blood correlated strongly with serum blood, and a certain correlation has also been found with nasal exudate. The electrochemical approach, combining sensitivity and precision with non-invasive sampling, offers a simplified alternative for IgE determination in allergic disease.

A Cost-Effective and Rapid Manufacturing Approach for Electrochemical Transducers with Magnetic Beads for Biosensing

Biosensors as advanced analytical tools have found various applications in food safety, healthcare, and environmental monitoring in rapid and specific detection of target analytes in small liquid samples. Up to now, planar electrochemical electrodes have shown the highest potential for biosensor applications due to their simple and compact construction and cost-effectiveness. Although a number of commercially available electrodes, manufactured from various materials on different substrates, can be found on the market, their high costs for single use and low reproducibility persist as major drawbacks. In this study, we present an innovative, cost-effective approach for the rapid fabrication of electrodes that combines lamination of 24-karat gold leaves with low-cost polyvinyl chloride adhesive sheets followed by laser ablation. Laser ablation enables the creation of electrodes with customizable geometries and patterns with microlevel resolutions. The developed electrodes are characterized by cyclic voltammetry and electrochemical impedance spectroscopy, scanning electronic microscopy, and 3D profiling. To demonstrate the manufacturing and biosensing potential, different geometries and shapes of electrodes were realized as the electrochemical transducing platform and applied for the realization of magnetic bead (MB)-labeled biosensors for quantitative detection of food-borne pathogens of Salmonella typhimurium (S. typhimurium) and Listeria monocytogenes (L. monocytogenes).

Overview and trends in electrochemical sensors, biosensors and cellular antioxidant assays for oxidant and antioxidant determination in food

Screening and quantifying antioxidants from food samples, their antioxidant activity, as well as the assessment of food oxidation is critical, not only for ensuring food quality and safety, but also to understand and relate these parameters to the shelf life, sensory attributes, and health aspects of food products. For this purpose, several methods have been developed and used for decades, which regardless of their effectiveness, present a certain number of drawbacks mainly related to extensive sample preparation and technical complexity, time requirements, and the use of hazardous chemicals. Electrochemical sensors and biosensors are gaining popularity in food analysis due to their high sensitivity, specificity, rapid response times, and potential for miniaturisation and portability. Furthermore, other modern methods using whole living cells such as the cellular antioxidant activity assay, the antioxidant power 1 assay, and the catalase-like assays, may interpret more realistic antioxidant results rather than just reporting the ability to scavenge free radicals in isolated systems with extrapolation to reality. This paper provides an overview of electrochemical sensors, biosensors, and cellular antioxidant assays, and reviews the latest advancements and emerging trends in these techniques for determining oxidants and antioxidants in complex food matrices. The performances of different strategies are described for each of these approaches to provide insights into the extent to which these methods can be exploited in the field and inspire new research to fill the current gaps.

Screen-Printing vs Additive Manufacturing Approaches: Recent Aspects and Trends Involving the Fabrication of Electrochemical Sensors

A few decades ago, the technological boom revolutionized access to information, ushering in a new era of research possibilities. Electrochemical devices have recently emerged as a key scientific advancement utilizing electrochemistry principles to detect various chemical species. These versatile electrodes find applications in diverse fields, such as healthcare diagnostics and environmental monitoring. Modern designs have given rise to innovative manufacturing protocols, including screen and additive printing methods, for creating sophisticated 2D and 3D electrochemical devices. This perspective provides a comprehensive overview of the screen-printing and additive-printing protocols for constructing electrochemical devices. It is also informed that screen-printed sensors offer cost-effectiveness and ease of fabrication, although they may pose challenges due to the use of toxic volatile inks and limited design flexibility. On the other hand, additive manufacturing, especially the fused filament fabrication (or fused deposition modeling) strategies, allows for intricate three-dimensional sensor designs and rapid prototyping of customized equipment. However, the post-treatment processes and material selection can affect production costs. Despite their unique advantages and limitations, both printing techniques show promise for various applications, driving innovation in the field toward more advanced sensor designs. Finally, these advancements pave the way for improved sensor performance and expand possibilities for academic, environmental, and industrial applications. The future is full of exciting opportunities for state-of-the-art sensor technologies that will further improve our ability to detect and determine various substances in a wide range of environments as researchers continue to explore the many possibilities of electrochemical devices.

Rapid microcystin-LR detection using antibody-based electrochemical biosensors with a simplified calibration curve approach

Harmful algal blooms (HABs) can release cyanotoxins such as microcystins (MCs), especially, microcystin-leucine-arginine (MC-LR) which is one of the commonest and most toxic, into our water bodies and can lead to several acute or chronic diseases such as liver diseases and respiratory irritation in humans. There is an increasing need for rapid and simple detection of MC-LR in water bodies for early warning of HABs. In this study, we developed an innovative on-site screening electrochemical impedance spectroscopy (EIS) biosensor with a simplified calibration curve that can rapidly detect blooms for early action in similar water bodies. The novel aspect of this research is that various chemical cleaning procedures and surface modifications were evaluated to improve the antibody-embedded electrochemical sensor performance. In addition, a simplified calibration curve was constructed from different water samples to reduce the need for frequent recalibration in practical applications. In this study, two distinct commercially available screen-printed carbon electrodes (SPCEs) were modified as a cost-effective substrate for MC-LR biosensing with anti-MC-LR/MC-LR/cysteamine-coating. The study showed that an appropriate cleaning procedure might minimize the sensor performance difference after each electrode modification. The biosensor showed excellent sensitivity toward MC-LR detection in lake water samples with a limit of detection (LOD) of 0.34 ngL-1. The simplified calibration curve was developed and used to predict unknown MC-LR concentrations in several lake water samples with a relative standard deviation (RSD) of 1.0-4.4% and a recovery of 75-112%, indicating the suitability of the developed biosensor and a streamlined calibration curve for rapid MC-LR measurements for different water bodies with similar water quality. This approach can therefore reduce the need for frequent calibration efforts and can be employed as the first line of testing for MC-LR in drinking and recreational water sources, especially in emergencies.

Laser-Treated Screen-Printed Carbon Electrodes for Electrochemiluminescence imaging

Electrochemiluminescence (ECL) is nowadays a powerful technique widely used in biosensing and imaging, offering high sensitivity and specificity for detecting and mapping biomolecules. Screen-printed electrodes (SPEs) offer a versatile and cost-effective platform for ECL applications due to their ease of fabrication, disposability, and suitability for large-scale production. This research introduces a novel method for improving the ECL characteristics of screen-printed carbon electrodes (SPCEs) through the application of CO2 laser treatment following fabrication. Using advanced ECL microscopy, we analyze three distinct carbon paste-based electrodes and show that low-energy laser exposure (ranging from 7 to 12 mJ·cm-2) enhances the electrochemical performance of the electrodes. This enhancement results from the selective removal of surface binders and contaminants achieved by the laser treatment. We employed ECL microscopy to characterize the ECL emission using a bead-based system incorporating magnetic microbeads, like those used in commercial platforms. This approach enabled high-resolution spatial mapping of the electrode surface, offering valuable insights into its electrochemical performance. Through quantitative assessment using a photomultiplier tube (PMT), it was observed that GST electrodes could detect biomarkers with high sensitivity, achieving an approximate detection limit (LOD) of 11 antibodies per μm2. These findings emphasize the potential of laser-modified GST electrodes in enabling highly sensitive electrochemiluminescent immunoassays and various biosensing applications.

Emergence of infectious diseases and role of advanced nanomaterials in point-of-care diagnostics: a review

Infectious outbreaks are the foremost global public health concern, challenging the current healthcare system, which claims millions of lives annually. The most crucial way to control an infectious outbreak is by early detection through point-of-care (POC) diagnostics. POC diagnostics are highly advantageous owing to the prompt diagnosis, which is economical, simple and highly efficient with remote access capabilities. In particular, utilization of nanomaterials to architect POC devices has enabled highly integrated and portable (compact) devices with enhanced efficiency. As such, this review will detail the factors influencing the emergence of infectious diseases and methods for fast and accurate detection, thus elucidating the underlying factors of these infections. Furthermore, it comprehensively highlights the importance of different nanomaterials in POCs to detect nucleic acid, whole pathogens, proteins and antibody detection systems. Finally, we summarize findings reported on nanomaterials based on advanced POCs such as lab-on-chip, lab-on-disc-devices, point-of-action and hospital-on-chip. To this end, we discuss the challenges, potential solutions, prospects of integrating internet-of-things, artificial intelligence, 5G communications and data clouding to achieve intelligent POCs.

Environmentally friendly screen-printed electrodes for the selective detection of 4-bromo-2,5-dimethoxyphenethylamine (2C-B) in forensic analysis

In response to the growing need for sustainable analytical methods, this study explores the repurposing of screen-printed electrodes (SPEs) that would otherwise be discarded. This involves recoating the working electrode surface with a graphite (Gr) and chitosan (CTS) dispersion, creating a reusable SPE (SPE-Gr/CTS). Demonstrating its utility, SPE-Gr/CTS was employed for the detection of 4-bromo-2,5-dimethoxyphenethylamine (2C-B), a phenylethylamine commonly used for recreational proposes. Identifying 2C-B in fluid oral and seized samples is of great interest for forensic and toxicological applications. The 2C-B detection using SPE-Gr/CTS was optimized in Britton-Robinson buffer solution (0.1 mol L-1) at pH 2.0, employing square-wave adsorptive stripping voltammetry. The electrochemical behavior of 2C-B on SPE-Gr/CTS exhibited one irreversible oxidation and a reversible redox process. The proposed method presented a dynamic linear range for 2C-B determination (0.05 to 7.5 μmol L-1) with a low LOD (0.015 μmol L-1). Moreover, the stability of 2C-B electrochemical responses on SPE-Gr/CTS was confirmed using the same or different electrodes (N = 3), with a relative standard deviation of less than 5.0%. Interference studies with seventeen other illicit drugs and adulterants demonstrated that the proposed method is selective for 2C-B detection even in the presence of these substances. Real seized and oral fluid samples containing 2C-B were analyzed using this method, and the results were confirmed by LC-MS. The proposed device demonstrates to be an environmentally friendly and selective sensor for 2C-B detection in forensic analysis, offering a rapid and straightforward screening method for seized and biological samples. In addition, a portable and sensitive determination of 2C-B in forensic samples is presented with minimal sample consumption (50 μL).

A highly sensitive and selective label-free impedimetric immunosensor for the detection of interleukin-6 based on AuNPs@pDA@NiCo2S4@MoS2 nanocomposite

A highly sensitive and selective label-free impedimetric immunosensor based on AuNPs@pDA@NiCo2S4@MoS2 nanocomposite modified on the surface of a screen-printed electrode (SPE) was designed for the detection of interleukin-6 (IL-6). The distribution of NiCo2S4 nanoparticles on MoS2 nanosheets was able to prevent them from agglomerating. The polydopamine (pDA) layer was coated on the surface of NiCo2S4@MoS2 nanosheets by self-polymerization, which improved the stability and biocompatibility of the nanomaterial. The excellent reduction ability of pDA promoted the synthesis of gold nanoparticles (AuNPs), which increased the amount of antibody adsorption and the conductivity of the material. Finally, the antibody (Ab) of IL-6 was immobilized on the surface of AuNPs@pDA@NiCo2S4@MoS2 nanocomposite. Electrochemical impedance spectroscopy (EIS) was used to detect the change of impedance before and after the immune response between Ab and IL-6 antigen (IL-6). Under the optimal experimental conditions, the relative change in impedance and the logarithmic concentration of IL-6 showed a good linear relationship in the range 1.00 to 1.00 × 106 pg/mL, with a low detection limit of 0.97 pg/mL. In addition, the proposed immunosensor performed with good reproducibility, stability, and specificity. It was successfully applied to the determination of IL-6 in patient's serum samples of head and neck carcinoma with recoveries of 98.40% to 106.5%. To sum up, the proposed label-free impedimetric immunosensor was successfully constructed for IL-6 detection in real samples.

Synthesis of Silver Nanoparticles and Gold Nanoparticles Used as Biosensors for the Detection of Human Serum Albumin-Diagnosed Kidney Disease

Background/Objectives: This study aims to develop a screen-printed carbon electrode (SPCE) modified with silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) for the detection of human serum albumin (HSA). The objectives include utilizing green synthesis methods for nanoparticle production and evaluating the electrochemical performance of the modified electrodes. Methods: AgNPs and AuNPs were synthesized using Phulae pineapple peel extract (PPA) as a reducing agent. The nanoparticles were characterized using UV-visible spectrophotometry (UV-vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The electrochemical performance of AgNP/SPCE and AuNP/SPCE was assessed by cyclic voltammetry (CV) studies, and the electrodes were functionalized with anti-HSA antibodies for HSA detection. Results: Characterization revealed spherical nanoparticles ranging from 10 to 30 nm. Both AgNP/SPCE and AuNP/SPCE demonstrated improved electrochemical performance compared to bare SPCEs. The modified sensors could detect serum albumin concentrations from 10 to 400 μg/mL, with high correlation values of 0.97 and 0.99 for AgNPs and AuNPs, respectively. Conclusions: This research demonstrates the potential of using agricultural waste for green synthesis of nanoparticles and highlights the application of AgNPs and AuNPs in developing sensitive biosensing platforms for the detection of human serum albumin.

Gold nanoparticles decorated kaolinite mineral modified screen-printed electrode: Use for simple, sensitive determination of gallic acid in food samples

The current study offers the nanomolar quantification of gallic acid (GAL) based on gold nanoparticles (AuNps) and kaolinite minerals (KNT) modified on a screen-printed electrode (SPE). The electrochemical behavior of GAL was performed using differential pulse voltammetry (DPV) in Britton Robinson (BR) buffer solution at pH 2.0 as a supporting electrolyte. Under the optimized DPV mode parameters, the oxidation peak current of GAL (at 0.72 V vs Ag/AgCl) increased linearly in the range between 0.002 μmolL-1 and 40.0 μmolL-1 with a detection limit of 0.50 nmolL-1. The effect of common interfering agents was also investigated. Finally, the applicability of the proposed method was verified by quantification analysis of GAL in black tea and pomegranate juice samples.

Glucose Oxidase-Based Glucose Biosensing with a Simple Dual Ag/AgCl Probe Conductivity Readout

We describe a conductometric assay of the enzymatic conversion of glucose to gluconic acid by dissolved glucose oxidase (GOx), using the generation of proton and gluconate from the reaction product dissociation for glucose detection. Simple basics of ionic conductivity, a silver/silver chloride wire pair, and a small applied potential translate glucose-dependent GOx activity into a scalable cell current. Enzyme immobilization and complex sensor design, involving extra nanomaterials or microfabrication of electrode structures, are entirely avoided, in contrast to all modern electrochemical glucose biosensors. Assay calibration showed a response linearity up to 500 μM, with a sensitivity of about 1.3 nA/μM. Selectivity tests excluded signals from sugars other than glucose, and glucose quantifications with recovery rates close to 100% were reached with a model sample and a beverage. Easy use of elementary physicochemical phenomena and a satisfactory performance are assets of the proposed non-amperometric glucose biosensing strategy. Assay integration into a planar dual electrode platform, with or without microfluidic application option, is feasible because of the simplicity of the sensor readout and suggests a route to affordable glucose analysis in beverage, food, and body fluid samples.

Fabrication of a graphite-paraffin carbon paste electrode and demonstration of its use in electrochemical detection strategies

Electrochemical detection methods hold many advantages over their optical counterparts, such as operation in complex sample matrices, low-cost and high volume manufacture and possible equipment miniaturisation. Despite these advantages, the use of electrochemical detection is currently limited in the clinical setting. There is a wide range of potential electrode materials, selected for optimal signal-to-noise ratios and reproducibility when detecting target analytes. The use of carbon paste electrodes (CPEs) for electrochemical detection can be limited by their analytical performance, however they remain very attractive due to their low cost and biocompatibility. This paper presents the fabrication of an easy-to-make and use graphite powder/paraffin wax paste combined with a substrate produced via additive manufacturing and confirms its functionality for both direct and indirect electrochemical measurements. The produced CPEs enable the direct voltammetric detection of hexaammineruthenium(III) chloride and dopamine at an experimental limit of detection (ELoD) of 62.5 μM. The key inflammatory biomarker Interleukin-6 through an enzyme-linked immunosorbant assay (ELISA) was also quantified, yielding a clinically-relevant ELoD of 150 pg ml-1 in 10% human serum. The performance of low-cost and easy-to-use CPEs obtained in 0.5 hours is showcased in this study, demonstrating the platform's potential uses for point-of-need electroanalytical applications.

Screen-Printed Electrodes as Low-Cost Sensors for Breast Cancer Biomarker Detection

This review explores the emerging role of screen-printed electrodes (SPEs) in the detection of breast cancer biomarkers. We discuss the fundamental principles and fabrication techniques of SPEs, highlighting their adaptability and cost-effectiveness. The review examines various modification strategies, including nanomaterial incorporation, polymer coatings, and biomolecule immobilization, which enhance sensor performance. We analyze the application of SPEs in detecting protein, genetic, and metabolite biomarkers associated with breast cancer, presenting recent advancements and innovative approaches. The integration of SPEs with microfluidic systems and their potential in wearable devices for continuous monitoring are explored. While emphasizing the promising aspects of SPE-based biosensors, we also address current challenges in sensitivity, specificity, and real-world applicability. The review concludes by discussing future perspectives, including the potential for early screening and therapy monitoring, and the steps required for clinical implementation. This comprehensive overview aims to stimulate further research and development in SPE-based biosensors for improved breast cancer management.

Applications of chemically modified screen-printed electrodes in food analysis and quality monitoring: a review

Food analysis and food quality monitoring are vital aspects of the food industry, ensuring the safety and authenticity of various food products, from packaged goods to fast food. In this comprehensive review, we explore the applications of chemically modified Screen-Printed Electrodes (SPEs) in these critical domains. SPEs have become extremely useful devices for ensuring food safety and quality assessment because of their adaptability, affordability, and convenience of use. The Introduction opens the evaluation, that covers a wide spectrum of foods, encompassing packaged, junk food, and food quality concerns. This sets the stage for a detailed exploration of chemically modified SPEs, including their nature, types, utilization, and the advantages they offer in the context of food analysis. Subsequently, the review delves into the multitude applications of SPEs in food analysis, ranging from the detection of microorganisms such as bacteria and fungi, which are significant indicators of food spoilage and safety, to the identification of pesticide residues, food colorants, chemicals, toxins, and antibiotics. Furthermore, chemically modified SPEs have proven to be invaluable in the quantification of metal ions and vitamins in various food matrices, shedding light on nutritional content and quality.

Disposable electrochemical sensors based on reduced graphene oxide/polyaniline/poly(alizarin red S)-modified integrated carbon electrodes for the detection of ciprofloxacin in milk

An electrochemical sensor based on an electroactive nanocomposite was designed for the first time consisting of electrochemically reduced graphene oxide (ERGO), polyaniline (PANI), and poly(alizarin red S) (PARS) for ciprofloxacin (CIPF) detection. The ERGO/PANI/PARS-modified screen-printed carbon electrode (SPCE) was constructed through a three-step electrochemical protocol and characterized using FTIR, UV-visible spectroscopy, FESEM, CV, LSV, and EIS. The new electrochemical CIPF sensor demonstrated a low detection limit of 0.0021 μM, a broad linear range of 0.01 to 69.8 μM, a high sensitivity of 5.09 μA/μM/cm2, and reasonable selectivity and reproducibility. Moreover, the ERGO/PANI/PARS/SPCE was successfully utilized to determine CIPF in milk with good recoveries and relative standard deviation (< 5%), which were close to those with HPLC analysis.

Development and characterization of a portable electrochemical aptasensor for IsdA protein and Staphylococcus aureus detection

Staphylococcus aureus (S. aureus) is recognized as one of the most common causes of gastroenteritis worldwide. This pathogen is a major foodborne pathogen that can cause many different types of various infections, from minor skin infections to lethal blood infectious diseases. Iron-regulated surface determinant protein A (IsdA) is an important protein on the S. aureus surface. It is responsible for iron scavenging via interaction with hemoglobin, haptoglobin, and hemoglobin-haptoglobin complexes. This study develops a portable aptasensor for IsdA and S. aureus detection using aptamer-modified gold nanoparticles (AuNPs) integrated into screen-printed carbon electrodes (SPCEs). The electrode system was made of three parts, including a carbon counter electrode, an AuNPs/carbon working electrode, and a silver reference electrode. The aptamer by Au-S bonding was conjugated on the electrode surface to create the aptasensor platform. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were utilized to investigate the binding interactions between the aptasensor and the IsdA protein. CV studies showed a linear correlation between varying S. aureus concentrations within the range of 101 to 106 CFU/mL, resulting in a limit of detection (LOD) of 0.2 CFU/mL. The results demonstrated strong reproducibility, selectivity, and sensitivity of the aptasensor for enhanced detection of IsdA, along with about 93% performance stability after 30 days. The capability of the aptasensor to directly detect S. aureus via the IsdA surface protein binding was further investigated in a food matrix. Overall, the aptasensor device showed the potential for rapid detection of S. aureus, serving as a robust approach to developing real-time aptasensors to identify an extensive range of targets of foodborne pathogens and beyond.

Nanomaterials-based electrochemical biosensors for diagnosis of COVID-19

Since the outbreak of corona virus disease 2019 (COVID-19), this pandemic has caused severe death and infection worldwide. Owing to its strong infectivity, long incubation period, and nonspecific symptoms, the early diagnosis is essential to reduce risk of the severe illness. The electrochemical biosensor, as a fast and sensitive technique for quantitative analysis of body fluids, has been widely studied to diagnose different biomarkers caused at different infective stages of COVID-19 virus (SARS-CoV-2). Recently, many reports have proved that nanomaterials with special architectures and size effects can effectively promote the biosensing performance on the COVID-19 diagnosis, there are few comprehensive summary reports yet. Therefore, in this review, we will pay efforts on recent progress of advanced nanomaterials-facilitated electrochemical biosensors for the COVID-19 detections. The process of SARS-CoV-2 infection in humans will be briefly described, as well as summarizing the types of sensors that should be designed for different infection processes. Emphasis will be supplied to various functional nanomaterials which dominate the biosensing performance for comparison, expecting to provide a rational guidance on the material selection of biosensor construction for people. Finally, we will conclude the perspective on the design of superior nanomaterials-based biosensors facing the unknown virus in future.

Wireless electrochemiluminescent biosensors: Powering innovation with smartphone technology

Energy supply and sensor response acquisition can be performed wirelessly, enabling biosensors as Internet of Thing (IoT) tools by linking wireless power supply and electrochemical sensors. Here, we used the electromagnetic induction method to clarify the conditions under which electrochemiluminescence is induced by a simple potential modulation circuit without an integrated circuit on the electrode chip that receives the power. Initially, the potential waveform obtained in a circuit with inductance and capacitance components that resonate with the transmission frequency and a diode for rectification was investigated to clarify the conditions inducing an electrochemiluminescence reaction at the printed electrode. A high-sensitivity complementary metal-oxide semiconductor camera built into the smartphone wirelessly detected the luminescence generated on the electrode chip. The images were quantitatively evaluated using open-source image analysis software which determine the sensitivity of detecting hydrogen peroxide. Glucose oxidase (GOD) encapsulated in a matrix of chitosan polymers and photocrosslinkable polymers was immobilized on a mass-producible and inexpensive printed electrode to maintain high activity. The immobilized membrane suppressed luminescence when immobilized on the working electrode; therefore, the enzyme was immobilized on the counter electrode for glucose measurement over a wide concentration. Thus, luminol electrochemiluminescence was induced on the electrode chip by wireless power supply from a smartphone. Human serum and artificial sweat samples were tested and indicated possibility for actual applications. In this way a fully wireless biosensor was developed with potential as an IoT biosensor.

Green Synthesis of Ceria Nanoparticles from Cassava Tubers for Electrochemical Aptasensor Detection of SARS-CoV-2 on a Screen-Printed Carbon Electrode

Green synthesis approaches for making nanosized ceria using starch from cassava as template molecules to control the particle size are reported. The results of the green synthesis of ceria with an optimum calcination temperature of 800 °C shows a size distribution of each particle of less than 30 nm with an average size of 9.68 nm, while the ratio of Ce3+ to Ce4+ was 25.6%. The green-synthesized nanoceria are applied to increase the sensitivity and attach biomolecules to the electrode surface of the electrochemical aptasensor system for coronavirus disease (COVID-19). The response of the aptasensor to the receptor binding domain of the virus was determined with the potassium ferricyanide redox system. The screen-printed carbon electrode that has been modified with green-synthesized nanoceria shows 1.43 times higher conductivity than the bare electrode, while those modified with commercial ceria increase only 1.18 times. Using an optimized parameter for preparing the aptasensors, the detection and quantification limits were 1.94 and 5.87 ng·mL-1, and the accuracy and precision values were 98.5 and 89.1%. These results show that green-synthesized ceria could be a promising approach for fabricating an electrochemical aptasensor.

Development of a sensitive electrochemical method to determine amitraz based on perylene tetracarboxylic acid/mesoporous carbon/Nafion@SPCEs

A cutting-edge electrochemical method is presented for precise quantification of amitraz (AMZ), a commonly used acaricide in veterinary medicine and agriculture. Leveraging a lab-made screen-printed carbon electrode modified with a synergistic blend of perylene tetracarboxylic acid (PTCA), mesoporous carbon (MC), and Nafion, the sensor's sensitivity was significantly improved. Fine-tuning of PTCA, MC, and Nafion ratios, alongside optimization of the pH of the supporting electrolyte and accumulation time, resulted in remarkable sensitivity enhancements. The sensor exhibited a linear response within the concentration range 0.01 to 0.70 μg mL-1, boasting an exceptionally low limit of detection of 0.002 μg mL-1 and a limit of quantification of 0.10 μg mL-1, surpassing maximum residue levels permitted in honey, tomato, and longan samples. Validation with real samples demonstrated high recoveries ranging from 80.8 to 104.8%, with a relative standard deviation below 10%, affirming the method's robustness and precision. The modified PTCA/MC/Nafion@SPCE-based electrochemical sensor not only offers superior sensitivity but also simplicity and cost-effectiveness, making it a pivotal tool for accurate AMZ detection in food samples. Furthermore, beyond the scope of this study, the sensor presents promising prospects for wider application across various electrochemical analytical fields, thereby significantly contributing to food safety and advancing agricultural practices.

Smart and emerging point of care electrochemical sensors based on nanomaterials for SARS-CoV-2 virus detection: Towards designing a future rapid diagnostic tool

In the recent years, researchers from all over the world have become interested in the fabrication of advanced and innovative electrochemical and/or biosensors for respiratory virus detection with the use of nanotechnology. These fabricated sensors demonstrated a number of benefits, including precision, affordability, accessibility, and miniaturization which makes them a promising test method for point-of-care (PoC) screening for SARS-CoV-2 viral infection. In order to comprehend the principles of electrochemical sensing and the role of various types of sensing interfaces, we comprehensively explored the underlying principles of electroanalytical methods and terminologies related to it in this review. In addition, it is addressed how to fabricate electrochemical sensing devices incorporating nanomaterials as graphene, metal/metal oxides, metal organic frameworks (MOFs), MXenes, quantum dots, and polymers. We took an effort to carefully compile current developments, advantages, drawbacks, possible solutions in nanomaterials based electrochemical sensors.

Rapid Detection and Identification of Vancomycin-Sensitive Bacteria Using an Electrochemical Apta-Sensor

In order to combat the complex and diverse infections caused by bacteria, it is essential to develop efficient diagnostic tools. Current techniques for bacterial detection rely on laborious multistep procedures, with high costs and extended time of analysis. To overcome these limitations, we propose here a novel portable electrochemical biosensor for the rapid detection and identification of Gram-positive bacteria that leverages the recognition capabilities of vancomycin and aptamers. A vancomycin-modified screen-printed carbon electrode was used to selectively capture Gram-positive bacteria susceptible to this antibiotic. Electrochemical impedance spectroscopy and scanning electron microscopy demonstrated that capture was achieved in 10 min, with a limit of detection of only 2 CFU/mL. We then tested the device's potential for aptamer-based bacterial identification using Staphylococcus aureus and Bacillus cereus as the test strains. Specifically, electrodes with captured bacteria were exposed to species-specific aptamers, and the resulting changes in current intensity were analyzed using differential pulse voltammetry. When used directly in untreated milk or serum, the system was able to successfully identify a small amount of S. aureus and B. cereus (100 CFU/mL) in less than 45 min. This novel biosensor has the potential to serve as an invaluable tool that could be used, even by inexperienced staff, in a broad range of settings including clinical diagnostics, food safety analysis, environmental monitoring, and security applications.

Disposable biosensor based on ionic liquid, carbon nanofiber and poly(glutamic acid) for tyramine determination

In this study, an electrochemical biosensor based on carbon nanofibers (CNF), ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (IL), poly(glutamic acid) (PGA) and tyrosinase (Tyr) modified screen printed carbon electrode (SPE) was constructed for tyramine determination. Optimum experimental parameters such as CNF and IL amount, polymerization conditions of glutamic acid, enzyme loading, pH of test solution and operating potential were explored. The construction steps of the Tyr/PGA/CNF-IL/SPE were pursued by scanning electron microscopy and cyclic voltammetry. The Tyr/PGA/CNF-IL/SPE biosensor exhibited linear response to tyramine in the range of 2.0 × 10-7 - 4.8 × 10-5 M with a low detection limit of 9.1 × 10-8 M and sensitivity of 302.6 μA mM-1. The other advantages of Tyr/PGA/CNF-IL/SPE include its high reproducibility, good stability and anti-interference ability. The presented biosensor was also applied for tyramine determination in malt drink and pickle juice samples and mean analytical recoveries of spiked tyramine were calculated as 100.6% and 100.4% respectively.

Disposable Molecularly Imprinted Polymer-Modified Screen-Printed Electrodes for Rapid Electrochemical Detection of l-Kynurenine in Human Urine

l-Kynurenine (l-Kyn) is an endogenous metabolite produced in the catabolic route of l-Tryptophan (l-Trp), and it is a potential biomarker of several immunological disorders. Thus, the development of a fast and cheap technology for the specific detection of l-Kyn in biological fluids is of great relevance, especially considering its recent correlation with SARS-CoV-2 disease progression. Herein, a disposable screen-printed electrode based on a molecularly imprinted polymer (MIP) has been constructed: the o-Phenylenediamine monomer, in the presence of l-Kyn as a template with a molar ratio of monomer/template of 1/4, has been electropolymerized on the surface of a screen-printed carbon electrode (SPCE). The optimized kyn-MIP-SPCE has been characterized via cyclic voltammetry (CV), using [Fe(CN)6)]3-/4- as a redox probe and a scanning electron microscopy (SEM) technique. After the optimization of various experimental parameters, such as the number of CV electropolymerization cycles, urine pretreatment, electrochemical measurement method and incubation period, l-Kyn has been detected in standard solutions via square wave voltammetry (SWV) with a linear range between 10 and 100 μM (R2 = 0.9924). The MIP-SPCE device allowed l-Kyn detection in human urine in a linear range of 10-1000 μM (R2 = 0.9902) with LOD and LOQ values of 1.5 and 5 µM, respectively. Finally, a high selectivity factor α (5.1) was calculated for l-Kyn toward l-Trp. Moreover, the Imprinting Factor obtained for l-Kyn was about seventeen times higher than the IF calculated for l-Trp. The developed disposable sensing system demonstrated its potential application in the biomedical field.

Self-assembling biomolecules for biosensor applications

Molecular self-assembly has received considerable attention in biomedical fields as a simple and effective method for developing biomolecular nanostructures. Self-assembled nanostructures can exhibit high binding affinity and selectivity by displaying multiple ligands/receptors on their surface. In addition, the use of supramolecular structure change upon binding is an intriguing approach to generate binding signal. Therefore, many self-assembled nanostructure-based biosensors have been developed over the past decades, using various biomolecules (e.g., peptides, DNA, RNA, lipids) and their combinations with non-biological substances. In this review, we provide an overview of recent developments in the design and fabrication of self-assembling biomolecules for biosensing. Furthermore, we discuss representative electrochemical biosensing platforms which convert the biochemical reactions of those biomolecules into electrical signals (e.g., voltage, ampere, potential difference, impedance) to contribute to detect targets. This paper also highlights the successful outcomes of self-assembling biomolecules in biosensor applications and discusses the challenges that this promising technology needs to overcome for more widespread use.

Recombinase polymerase amplification in combination with electrochemical readout for sensitive and specific detection of PIK3CA point mutations

As part of the ongoing evolution towards personalized anticancer therapy, mutation screening is becoming increasingly important and, therefore, also alternative detection strategies that allow for fast genetic diagnostics at the point of care. In the case of breast cancer, detecting cancer-associated point mutations in the PIK3CA gene is of particular importance for treatment decisions. We developed a recombinase polymerase amplification assay combined with an enzyme-linked electrochemical assay on multi-channel screen-printed gold sensors for specific and highly sensitive detection of three PIK3CA point mutations (H1047R, E545K, and E542K). Recombinase polymerase amplification (RPA) of the target sequences was optimized and characterized with a real-time RPA assay. Comparison with real-time PCR reveals that RPA is slightly inferior in terms of efficiency and sensitivity. However, the desired target DNA is successfully amplified at initial concentrations down to 100 copies μL-1. For electrochemical readout, biotinylated dCTP is used to label the target DNA during RPA. Single-stranded target DNA is produced with either asymmetric RPA or symmetric RPA followed by lambda exonuclease digestion. Characterization of the two different approaches in terms of sensitivity results in comparable detection limits (229 copies μL-1 and 224 copies μL-1, respectively), though RPA followed by lambda exonuclease digestion yields significantly higher currents. Finally, this method, together with a designed wild-type blocking oligo that inhibits binding of the wild-type target DNA during probe-target hybridization, allows for detecting the PIK3CA point mutations H1047R, E545K, and E542K in the presence of wild-type target DNA when the proportion of mutant target DNA is >20%.

A molecularly imprinted screen-printed carbon electrode for electrochemical epinephrine, lactate, and cortisol metabolites detection in human sweat

This study presents a novel approach to the detection of epinephrine, lactate, and cortisol biomarkers in human sweat using molecularly-imprinted polymers (MIP) embedded screen printed carbon electrode (SPCE) sensors. The epinephrine and lactate MIP SPCE sensors were fabricated by epinephrine or lactate-imprinted polyaniline co-polymerized with 3-aminophenylboronic acid and gold nanoparticles (PANI-co-PBA/AuNP) selective membrane on a commercial SPCE. The cortisol sensor was comprised of a cortisol-imprinted poly(glycidyl methacryate-co-ethylene glycol dimethacrylate) (poly (GMA-co-EGDMA)@AuNP selective membrane deposited on a SPCE. Both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as modes of analysis for the MIP SPCE sensors. All sensors exhibited a rapid (∼1 min) and selective response to the epinephrine, lactate, and cortisol target analytes, with excellent precision between scans for both CV and DPV analysis modes. For CV, the LOD for epinephrine, lactate, and cortisol was 8.2 nM, 13 mM, and 0.042 μM, respectively. The LOD for DPV were 0.60 nM, 2.2 mM, and 0.025 μM for epinephrine, lactate, and cortisol, respectively. The MIP SPCE sensor platforms were further validated through the successful quantification of epinephrine, lactate, and cortisol in human sweat.

Bacteria-Infected Artificial Urine Characterization Based on a Combined Approach Using an Electronic Tongue Complemented with 1H-NMR and Flow Cytometry

The prevailing form of bacterial infection is within the urinary tract, encompassing a wide array of bacteria that harness the urinary metabolome for their growth. Through their metabolic actions, the chemical composition of the growth medium undergoes modifications as the bacteria metabolize urine compounds, leading to the subsequent release of metabolites. These changes can indirectly indicate the existence and proliferation of bacterial organisms. Here, we investigate the use of an electronic tongue, a powerful analytical instrument based on a combination of non-selective chemical sensors with a partial specificity for data gathering combined with principal component analysis, to distinguish between infected and non-infected artificial urine samples. Three prevalent bacteria found in urinary tract infections were investigated, Escherichia coli, Klebsiella pneumoniae, and Enterococcus faecalis. Furthermore, the electronic tongue analysis was supplemented with 1H NMR spectroscopy and flow cytometry. Bacteria-specific changes in compound consumption allowed for a qualitative differentiation between artificial urine medium and bacterial growth.

Rapid integration of screen-printed electrodes into thermoplastic organ-on-a-chip devices for real-time monitoring of trans-endothelial electrical resistance

Trans-endothelial electrical resistance (TEER) is one of the most widely used indicators to quantify the barrier integrity of endothelial layers. Over the last decade, the integration of TEER sensors into organ-on-a-chip (OOC) platforms has gained increasing interest for its efficient and effective measurement of TEER in OOCs. To date, microfabricated electrodes or direct insertion of wires has been used to integrate TEER sensors into OOCs, with each method having advantages and disadvantages. In this study, we developed a TEER-SPE chip consisting of carbon-based screen-printed electrodes (SPEs) embedded in a poly(methyl methacrylate) (PMMA)-based multi-layered microfluidic device with a porous poly(ethylene terephthalate) membrane in-between. As proof of concept, we demonstrated the successful cultures of hCMEC/D3 cells and the formation of confluent monolayers in the TEER-SPE chip and obtained TEER measurements for 4 days. Additionally, the TEER-SPE chip could detect changes in the barrier integrity due to shear stress or an inflammatory cytokine (i.e., tumor necrosis factor-α). The novel approach enables a low-cost and facile fabrication of carbon-based SPEs on PMMA substrates and the subsequent assembly of PMMA layers for rapid prototyping. Being cost-effective and cleanroom-free, our method lowers the existing logistical and technical barriers presenting itself as another step forward to the broader adoption of OOCs with TEER measurement capability.

Aerogel-Based Biomaterials for Biomedical Applications: From Fabrication Methods to Disease-Targeting Applications

Aerogel-based biomaterials are increasingly being considered for biomedical applications due to their unique properties such as high porosity, hierarchical porous network, and large specific pore surface area. Depending on the pore size of the aerogel, biological effects such as cell adhesion, fluid absorption, oxygen permeability, and metabolite exchange can be altered. Based on the diverse potential of aerogels in biomedical applications, this paper provides a comprehensive review of fabrication processes including sol-gel, aging, drying, and self-assembly along with the materials that can be used to form aerogels. In addition to the technology utilizing aerogel itself, it also provides insight into the applicability of aerogel based on additive manufacturing technology. To this end, how microfluidic-based technologies and 3D printing can be combined with aerogel-based materials for biomedical applications is discussed. Furthermore, previously reported examples of aerogels for regenerative medicine and biomedical applications are thoroughly reviewed. A wide range of applications with aerogels including wound healing, drug delivery, tissue engineering, and diagnostics are demonstrated. Finally, the prospects for aerogel-based biomedical applications are presented. The understanding of the fabrication, modification, and applicability of aerogels through this study is expected to shed light on the biomedical utilization of aerogels.

3D-printed holder for drawing highly reproducible pencil-on-paper electrochemical devices

Pencil drawing is one of the simplest and most cost-effective ways of fabricating miniaturized electrodes on a paper substrate. However, it is limited by the lack of reproducibility regarding the electrode drawing process. A 3D-printed pencil holder (3DPH) is proposed here for simple, reproducible, and low-cost hand-drawn fabrication of paper-based electrochemical devices. 3DPH was designed to keep pressure and angulation of the graphite mine constant on the paper substrate using a micromechanical pencil regardless of the user/operator. This approach significantly improved the reproducibility and cost of making reliable pencil-drawn electrodes. The results showed high reproducibility and accuracy of the 3DPH-assisted electrodes prepared by 4 different operators in terms of sheet resistance and electrochemical behavior. Cyclic voltammetric (CV) curves in the presence of [Fe(CN)₆]^3-/4- redox probe showed only 3.9% variation for the anodic peak currents of different electrodes prepared by different operators when compared with electrodes prepared without the 3D-printed support. SEM analyses revealed a more uniform graphite deposition/design of the electrodes prepared with 3DPH, which corroborates the results obtained by CV. As a proof of concept, 3DPH-assisted pencil-drawn graphite electrodes were employed for dopamine detection in synthetic saliva, showing a proportional increase in anodic peak current at 0.12 V vs. carbon pRE with increasing dopamine (DA) concentration, with a detection limit of 0.39μmol L^-1. Moreover recovery was in the range 93-104% of DA (4-7% RSD) in synthetic saliva for three different concentrations, demonstrating the reliability of the approach. Finally, we believe this approach can make pencil-drawn technology more robust, accessible, reliable, and inexpensive for real on-site applications, especially in hard-to-reach locations or research centers with little investment.

Fabric-Based Electrochemical Glucose Sensor with Integrated Millifluidic Path from a Hydrophobic Batik Wax

In recent years, measuring and monitoring analyte concentrations continuously, frequently, and periodically has been a vital necessity for certain individuals. We developed a cotton-based millifluidic fabric-based electrochemical device (mFED) to monitor glucose continuously and evaluate the effects of mechanical deformation on the device's electrochemical performance. The mFED was fabricated using stencil printing (thick film method) for patterning the electrodes and wax-patterning to make the reaction zone. The analytical performance of the device was carried out using the chronoamperometry method at a detection potential of -0.2 V. The mFED has a linear working range of 0-20 mM of glucose, with LOD and LOQ of 0.98 mM and 3.26 mM. The 3D mFED shows the potential to be integrated as a wearable sensor that can continuously measure glucose under mechanical deformation.

Electrochemical Impedance Spectroscopy-A Tutorial

This tutorial provides the theoretical background, the principles, and applications of Electrochemical Impedance Spectroscopy (EIS) in various research and technological sectors. The text has been organized in 17 sections starting with basic knowledge on sinusoidal signals, complex numbers, phasor notation, and transfer functions, continuing with the definition of impedance in electrical circuits, the principles of EIS, the validation of the experimental data, their simulation to equivalent electrical circuits, and ending with practical considerations and selected examples on the utility of EIS to corrosion, energy related applications, and biosensing. A user interactive excel file showing the Nyquist and Bode plots of some model circuits is provided in the Supporting Information. This tutorial aspires to provide the essential background to graduate students working on EIS, as well as to endow the knowledge of senior researchers on various fields where EIS is involved. We also believe that the content of this tutorial will be a useful educational tool for EIS instructors.

Recent advances in gold electrode fabrication for low-resource setting biosensing

Gold electrodes are some of the most prevalent electrochemical biosensor substrate materials because they are readily functionalized with thiolated biomolecules. Yet, conventional methods to fabricate gold electrodes are costly and require onerous equipment, precluding them from implementation in low-resource settings (LRS). Recently, a number of alternative gold electrode fabrication methods have been developed to simplify and lower the cost of manufacturing. These methods include screen and inkjet printing as well as physical fabrication with common materials such as wire or gold leaf. All electrodes generated with these methods have successfully been functionalized with thiolated molecules, demonstrating their suitability for use in biosensors. Here, we detail recent advances in the fabrication, characterization and functionalization of these next-generation gold electrodes, with an emphasis on comparisons between cost and complexity with traditional cleanroom fabrication. We highlight gold leaf electrodes for their potential in LRS. This class of electrodes is anticipated to be broadly applicable beyond LRS due to their numerous inherent advantages.

Electrochemical Capillary Driven Immunoassay for Detection of SARS-CoV-2

The COVID-19 pandemic focused attention on a pressing need for fast, accurate, and low-cost diagnostic tests. This work presents an electrochemical capillary driven immunoassay (eCaDI) developed to detect SARS-CoV-2 nucleocapsid (N) protein. The low-cost flow device is made of polyethylene terephthalate (PET) and adhesive films. Upon addition of a sample, reagents and washes are sequentially delivered to an integrated screen-printed carbon electrode for detection, thus automating a full sandwich immunoassay with a single end-user step. The modified electrodes are sensitive and selective for SARS-CoV-2 N protein and stable for over 7 weeks. The eCaDI was tested with influenza A and Sindbis virus and proved to be selective. The eCaDI was also successfully applied to detect nine different SARS-CoV-2 variants, including Omicron.

Aptamer-Based Electrochemical Biosensors for the Detection of Salmonella: A Scoping Review

The development of rapid, accurate, and efficient detection methods for Salmonella can significantly control the outbreak of salmonellosis that threatens global public health. Despite the high sensitivity and specificity of the microbiological, nucleic-acid, and immunological-based methods, they are impractical for detecting samples outside of the laboratory due to the requirement for skilled individuals and sophisticated bench-top equipment. Ideally, an electrochemical biosensor could overcome the limitations of these detection methods since it offers simplicity for the detection process, on-site quantitative analysis, rapid detection time, high sensitivity, and portability. The present scoping review aims to assess the current trends in electrochemical aptasensors to detect and quantify Salmonella. This review was conducted according to the latest Preferred Reporting Items for Systematic review and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. A literature search was performed using aptamer and Salmonella keywords in three databases: PubMed, Scopus, and Springer. Studies on electrochemical aptasensors for detecting Salmonella published between January 2014 and January 2022 were retrieved. Of the 787 studies recorded in the search, 29 studies were screened for eligibility, and 15 studies that met the inclusion criteria were retrieved for this review. Information on the Salmonella serovars, targets, samples, sensor specification, platform technologies for fabrication, electrochemical detection methods, limit of detection (LoD), and detection time was discussed to evaluate the effectiveness and limitations of the developed electrochemical aptasensor platform for the detection of Salmonella. The reported electrochemical aptasensors were mainly developed to detect Salmonella enterica Typhimurium in chicken meat samples. Most of the developed electrochemical aptasensors were fabricated using conventional electrodes (13 studies) rather than screen-printed electrodes (SPEs) (two studies). The developed aptasensors showed LoD ranges from 550 CFU/mL to as low as 1 CFU/mL within 5 min to 240 min of detection time. The promising detection performance of the electrochemical aptasensor highlights its potential as an excellent alternative to the existing detection methods. Nonetheless, more research is required to determine the sensitivity and specificity of the electrochemical sensing platform for Salmonella detection, particularly in human clinical samples, to enable their future use in clinical practice.

Potential application of nanotechnology in the treatment, diagnosis, and prevention of schistosomiasis

Schistosomiasis is one of the neglected tropical diseases that affect millions of people worldwide. Globally, it affects economically poor countries, typically due to a lack of proper sanitation systems, and poor hygiene conditions. Currently, no vaccine is available against schistosomiasis, and the preferred treatment is chemotherapy with the use of praziquantel. It is a common anti-schistosomal drug used against all known species of Schistosoma. To date, current treatment primarily the drug praziquantel has not been effective in treating Schistosoma species in their early stages. The drug of choice offers low bioavailability, water solubility, and fast metabolism. Globally drug resistance has been documented due to overuse of praziquantel, Parasite mutations, poor treatment compliance, co-infection with other strains of parasites, and overall parasitic load. The existing diagnostic methods have very little acceptability and are not readily applied for quick diagnosis. This review aims to summarize the use of nanotechnology in the treatment, diagnosis, and prevention. It also explored safe and effective substitute approaches against parasitosis. At this stage, various nanomaterials are being used in drug delivery systems, diagnostic kits, and vaccine production. Nanotechnology is one of the modern and innovative methods to treat and diagnose several human diseases, particularly those caused by parasite infections. Herein we highlight the current advancement and application of nanotechnological approaches regarding the treatment, diagnosis, and prevention of schistosomiasis.

Electrochemical Sensor for the Determination of Methylthiouracil in Meat Samples

Two analytical methods based on miniaturized electrochemical sensors, voltammetric and amperometric sensors, have been developed for the determination of 6-methyl-2-thiouracil (MTU) in meat consumption samples (beef liver and foie). A multivariate approach has been considered to optimize the experimental procedure including extraction and electrochemical detection. Under optimal conditions and at a typical working potential of 1.55 V (vs Ag pseudo-reference electrode), response is linear in the range 0 to 20 µg L−1 MTU concentration range. The empirical limit of detection is 0.13 µg L−1, lower than the maximum concentration established by legislation. The electrochemical methods have been used to analyze MTU-spiked meat samples, and recovery values varying between 85 and 95% with coefficients of variation <30%. The analytical methods developed with the miniaturized electrochemical sensors can successfully determine the concentration of MTU in real meat samples with high accuracy, being the results obtained similar to those provided by other methods such as UV-Vis spectrophotometry. Finally, the degree of sustainability of the electrochemical sensors-based developed method has been quantified by means of the Analytical Eco-Scale.

All-Solid State Potentiometric Sensors for Desvenlafaxine Detection Using Biomimetic Imprinted Polymers as Recognition Receptors

Using single-walled carbon nanotubes (SWCNTs) as an ion-to-electron transducer, a novel disposable all-solid-state desvenlafaxine-selective electrode based on a screen-printed carbon paste electrode was created. SWCNTs were put onto the carbon-paste electrode area, which was protected by a poly (vinyl chloride) (PVC) membrane with a desvenlafaxine-imprinted polymer serving as a recognition receptor. Electrochemical impedance spectroscopy and chronopotentiometric techniques were used to examine the electrochemical characteristics of the SWCNTs/PVC coating on the carbon screen-printed electrode. The electrode displayed a 57.2 ± 0.8 mV/decade near-Nernstian slope with a 2.0 × 10^-6 M detection limit. In 10 mM phosphate buffer, pH 6, the ODV-selective electrodes displayed a quick reaction (5 s) and outstanding stability, repeatability, and reproducibility. The usefulness of electrodes was demonstrated in samples of ODV-containing pharmaceutical products and human urine. These electrodes have the potential to be mass produced and employed as disposable sensors for on-site testing, since they are quick, practical, and inexpensive.

Electrochemical Biosensors for Pathogen Detection: An Updated Review

Electrochemical biosensors are a family of biosensors that use an electrochemical transducer to perform their functions. In recent decades, many electrochemical biosensors have been created for pathogen detection. These biosensors for detecting infections have been comprehensively studied in terms of transduction elements, biorecognition components, and electrochemical methods. This review discusses the biorecognition components that may be used to identify pathogens. These include antibodies and aptamers. The integration of transducers and electrode changes in biosensor design is a major discussion topic. Pathogen detection methods can be categorized by sample preparation and secondary binding processes. Diagnostics in medicine, environmental monitoring, and biothreat detection can benefit from electrochemical biosensors to ensure food and water safety. Disposable and reusable biosensors for process monitoring, as well as multiplexed and conformal pathogen detection, are all included in this review. It is now possible to identify a wide range of diseases using biosensors that may be applied to food, bodily fluids, and even objects' surfaces. The sensitivity of optical techniques may be superior to electrochemical approaches, but optical methods are prohibitively expensive and challenging for most end users to utilize. On the other hand, electrochemical approaches are simpler to use, but their efficacy in identifying infections is still far from satisfactory.

A Novel Activated Biochar-Based Immunosensor for Rapid Detection of E. coli O157:H7

E. coli O157:H7, one of the major foodborne pathogens, can cause a significant threat to the safety of foods. The aim of this research is to develop an activated biochar-based immunosensor that can rapidly detect E. coli O157:H7 cells without incubation in pure culture. Biochar was developed from corn stalks using proprietary reactors and then activated using steam-activation treatment. The developed activated biochar presented an enhanced surface area of 830.78 m²/g. To develop the biosensor, the gold electrode of the sensor was first coated with activated biochar and then functionalized with streptavidin as a linker and further immobilized with biotin-labeled anti-E. coli polyclonal antibodies (pAbs). The optimum concentration of activated biochar for sensor development was determined to be 20 mg/mL. Binding of anti-E. coli pAbs with E. coli O157:H7 resulted in a significant increase in impedance amplitude from 3.5 to 8.5 kΩ when compared to an only activated biochar-coated electrode. The developed immunosensor was able to detect E. coli O157:H7 cells with a limit of detection of 4 log CFU/mL without incubation. Successful binding of E. coli O157:H7 onto an activated biochar-based immunosensor was observed on the microelectrode surface in scanning electron microscopy (SEM) images.

A microfluidic electrochemical sensing platform for in situ detection of trace cadmium ions

Among various detection and analysis platforms, a microfluidic chip-based electrochemical sensing detection platform is a new type of detection platform. In this study, a microfluidic electrochemical detection platform for cadmium ion detection is proposed, and the performance of the detection platform is optimized in terms of both the microchannel size and electrode modifications. The detection mixing processes of the detector with different microchannel sizes, including the concentration distribution in the channel, pressure decay variation and electrolyte current density variation in the detector, were investigated by finite element model calculations. The analysis shows that the size of the microchannel in the detector affects the fluid and thus further affects the chemical reaction. If the size of the electrode does not match the size of the microchannel, insufficient sample volume will lead to inaccurate measurements, reduced sensitivity and increased detection limits. It was found that the sensitivity of the electrochemical sensor was highest when the size of the microchannel in the chip was 400 μm. After optimization, the optimal detection limit for cadmium ions was 0.03 μg L^-1 (S/N = 3). The proposed sensing platform is simple in design and stable in structure, and is suitable for field screening and rapid response to heavy metal contamination events.

Chronoampermetric detection of enzymatic glucose sensor based on doped polyindole/MWCNT composites modified onto screen-printed carbon electrode as portable sensing device for diabetes

Doped-polyindole (dPIn) mixed with multi-walled carbon nanotubes (MWCNTs) were coated on a screen-printed electrode to improve the electroactive surface area and current response of the chronoamperometric enzymatic glucose sensor. Glucose oxidase mixed with chitosan (CHI-GOx) was immobilized on the electrode. (3-Aminopropyl) triethoxysilane (APTES) was used as a linker between the CHI-GOx and the dPIn. The current response of the glucose sensor increased with increasing glucose concentration according to a power law relation. The sensitivity of the CHI-GOx/APTES/dPIn was 55.7 μA mM⁻¹ cm⁻² with an LOD (limit of detection) of 0.01 mM, where the detectable glucose concentration range was 0.01–50 mM. The sensitivity of the CHI-GOx/APTES/1.5%MWCNT-dPIn was 182.9 μA mM⁻¹ cm⁻² with an LOD of 0.01 mM, where the detectable glucose concentration range was 0.01–100 mM. The detectable concentration ranges of glucose well cover the glucose concentrations in urine and blood. The fabricated enzymatic glucose sensors showed high stability during a storage period of four weeks and high selectivity relative to other interferences. Moreover, the sensor was successfully demonstrated as a continuous or step-wise glucose monitoring device. The preparation method employed here was facile and suitable for large quantity production. The glucose sensor fabricated here, consisting of the three-electrode cell of SPCE, were simple to use for glucose detection. Thus, it is promising to use as a prototype for real glucose monitoring for diabetic patients in the future.

The enzymatic glucose sensor based on a dPIn and dPIn/MWCNT modified screen-printed carbon electrode with a facile method possessed good glucose response. The detectable glucose concentration range covers well the glucose concentrations in urine and blood.