Electrochemical Biosensors for Medical and Food Applications

Combining plasmonic and electrochemical biosensing methods

The idea of combining electrochemical (EC) and plasmonic biosensor methods was introduced almost thirty years ago and the potential of electrochemical-plasmonic (EC-P) biosensors has been highlighted ever since. Despite that, the use of EC-P biosensors in analytics has been rather limited so far and the search for unique applications of the EC-P method continues. In this paper, we review the advances in the field of EC-P biosensors and discuss the features and benefits they can provide. In addition, we identify the main challenges for the development of EC-P biosensors and the limitations that prevent EC-P biosensors from more widespread use. Finally, we review applications of EC-P biosensors for the investigation and quantification of biomolecules, and for the study of biomolecular and cellular processes.

Modern Electrochemical Biosensing Based on Nucleic Acids and Carbon Nanomaterials

To meet the requirements of novel therapies, effective treatments should be supported by diagnostic tools characterized by appropriate analytical and working parameters. These are, in particular, fast and reliable responses that are proportional to analyte concentration, with low detection limits, high selectivity, cost-efficient construction, and portability, allowing for the development of point-of-care devices. Biosensors using nucleic acids as receptors has turned out to be an effective approach for meeting the abovementioned requirements. Careful design of the receptor layers will allow them to obtain DNA biosensors that are dedicated to almost any analyte, including ions, low and high molecular weight compounds, nucleic acids, proteins, and even whole cells. The impulse for the application of carbon nanomaterials in electrochemical DNA biosensors is rooted in the possibility to further influence their analytical parameters and adjust them to the chosen analysis. Such nanomaterials enable the lowering of the detection limit, the extension of the biosensor linear response, or the increase in selectivity. This is possible thanks to their high conductivity, large surface-to-area ratio, ease of chemical modification, and introduction of other nanomaterials, such as nanoparticles, into the carbon structures. This review discusses the recent advances on the design and application of carbon nanomaterials in electrochemical DNA biosensors that are dedicated especially to modern medical diagnostics.

Recent Developments in DNA-Nanotechnology-Powered Biosensors for Zika/Dengue Virus Molecular Diagnostics

Zika virus (ZIKV) and dengue virus (DENV) are highly contagious and lethal mosquito-borne viruses. Global warming is steadily increasing the probability of ZIKV and DENV infection, and accurate diagnosis is required to control viral infections worldwide. Recently, research on biosensors for the accurate diagnosis of ZIKV and DENV has been actively conducted. Moreover, biosensor research using DNA nanotechnology is also increasing, and has many advantages compared to the existing diagnostic methods, such as polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). As a bioreceptor, DNA can easily introduce a functional group at the 5' or 3' end, and can also be used as a folded structure, such as a DNA aptamer and DNAzyme. Instead of using ZIKV and DENV antibodies, a bioreceptor that specifically binds to viral proteins or nucleic acids has been fabricated and introduced using DNA nanotechnology. Technologies for detecting ZIKV and DENV can be broadly divided into electrochemical, electrical, and optical. In this review, advances in DNA-nanotechnology-based ZIKV and DENV detection biosensors are discussed.

Recent Advances in Enzymatic and Non-Enzymatic Electrochemical Glucose Sensing

The detection of glucose is crucial in the management of diabetes and other medical conditions but also crucial in a wide range of industries such as food and beverages. The development of glucose sensors in the past century has allowed diabetic patients to effectively manage their disease and has saved lives. First-generation glucose sensors have considerable limitations in sensitivity and selectivity which has spurred the development of more advanced approaches for both the medical and industrial sectors. The wide range of application areas has resulted in a range of materials and fabrication techniques to produce novel glucose sensors that have higher sensitivity and selectivity, lower cost, and are simpler to use. A major focus has been on the development of enzymatic electrochemical sensors, typically using glucose oxidase. However, non-enzymatic approaches using direct electrochemistry of glucose on noble metals are now a viable approach in glucose biosensor design. This review discusses the mechanisms of electrochemical glucose sensing with a focus on the different generations of enzymatic-based sensors, their recent advances, and provides an overview of the next generation of non-enzymatic sensors. Advancements in manufacturing techniques and materials are key in propelling the field of glucose sensing, however, significant limitations remain which are highlighted in this review and requires addressing to obtain a more stable, sensitive, selective, cost efficient, and real-time glucose sensor.

Electrochemical Biosensors in Food Safety: Challenges and Perspectives

Safety and quality are key issues for the food industry. Consequently, there is growing demand to preserve the food chain and products against substances toxic, harmful to human health, such as contaminants, allergens, toxins, or pathogens. For this reason, it is mandatory to develop highly sensitive, reliable, rapid, and cost-effective sensing systems/devices, such as electrochemical sensors/biosensors. Generally, conventional techniques are limited by long analyses, expensive and complex procedures, and skilled personnel. Therefore, developing performant electrochemical biosensors can significantly support the screening of food chains and products. Here, we report some of the recent developments in this area and analyze the contributions produced by electrochemical biosensors in food screening and their challenges.

An innovative and user-friendly smartphone-assisted molecular diagnostic approach for rapid detection of canine vector-borne diseases

Present-day diagnostic tools and technologies for canine diseases and other vector-borne parasitic diseases hardly meet the requirements of an efficient and rapid diagnostic tool, which can be suitable for use at the point-of-care in resource-limited settings. Loop-mediated isothermal amplification (LAMP) technique has been always a method of choice in the development and validation of quick, precise, and sensitive diagnostic assays for pathogen detection and to reorganize point-of-care (POC) molecular diagnostics. In this study, we have demonstrated an efficient detection system for parasitic vector-borne pathogens like Ehrlichia canis and Hepatozoon canis by linking the LAMP assay to a smartphone via a simple, inexpensive, and a portable “LAMP box,” All the components of the LAMP box were connected to each other wirelessly. This LAMP box was made up of an isothermal heating pad mounted below an aluminum base which served as a platform for the reaction tubes and LAMP assay. The entire setup could be connected to a smartphone via an inbuilt Wi-Fi that allowed the user to establish the connection to control the LAMP box. A 5 V USB power source was used as a power supply. The sensitivity of the LAMP assay was estimated to be up to 10⁻⁶ dilution limit using the amplified, purified, and quantified specific DNA templates. It can also serve as an efficient diagnostic platform for many other veterinary infectious or parasitic diseases of zoonotic origin majorly towards field-based diagnostics.

Monitoring and control of E. coli cell integrity

Soluble expression of recombinant proteins in E. coli is often done by translocation of the product across the inner membrane (IM) into the periplasm, where it is retained by the outer membrane (OM). While the integrity of the IM is strongly coupled to viability and impurity release, a decrease in OM integrity (corresponding to increased "leakiness") leads to accumulation of product in the extracellular space, strongly impacting the downstream process. Whether leakiness is desired or not, differential monitoring and control of IM and OM integrity are necessary for an efficient E. coli bioprocess in compliance with the guidelines of Quality by Design and Process Analytical Technology. In this review, we give an overview of relevant monitoring tools, summarize the research on factors affecting E. coli membrane integrity and provide a brief discussion on how the available monitoring technology can be implemented in real-time control of E. coli cultivations.

Advances in Electrochemical Aptasensors Based on Carbon Nanomaterials

Carbon nanomaterials offer unique opportunities for the assembling of electrochemical aptasensors due to their high electroconductivity, redox activity, compatibility with biochemical receptors and broad possibilities of functionalization and combination with other auxiliary reagents. In this review, the progress in the development of electrochemical aptasensors based on carbon nanomaterials in 2016–2020 is considered with particular emphasis on the role of carbon materials in aptamer immobilization and signal generation. The synthesis and properties of carbon nanotubes, graphene materials, carbon nitride, carbon black particles and fullerene are described and their implementation in the electrochemical biosensors are summarized. Examples of electrochemical aptasensors are classified in accordance with the content of the surface layer and signal measurement mode. In conclusion, the drawbacks and future prospects of carbon nanomaterials’ application in electrochemical aptasensors are briefly discussed.

Electrochemical Study of Dimensional Specific Carbon Nanomaterials Modified Glassy Carbon Electrode for Highly Sensitive Label-free Detection of Immunoglobulin A

Background:

Immunoglobulin A (IgA) accounts for 15% of total protein production per day and plays a crucial role in the first-line immune defence. Recently, IgA has been established as a vital clinical biomarker for nephropathy, allergic asthma, celiac disease (CD), pneumonia, and asthma as well as some neurological disorders. In this work, we have studied several carbon nanomaterials (CNMs) having different dimensions (D): carbon nano-onions (CNOs) - 0D, single-walled carbon nanotubes (SWCNTs) - 1D, and graphene nanoplatelets (GNPs) - 2D, on glassy carbon electrode (GCE) to identify which CNMs (CNOs/SWCNTs/GNPs) work best to fabricate IgA based electrochemical immunosensor.

Methods:

Different CNMs (CNOs, SWCNTs, GNPs) were tested for high electric current on GCE using square wave voltammetry (SWV), and among them, GNPs modified GCE platform (GNPs/GCE) showcased the highest electric current. Therefore, GNPs/GCE was utilized for the development of highly sensitive label-free electrochemical immunosensor for the detection of Immunoglobulin A using SWV.

Results:

Despite the simple fabrication strategies employed, the fabricated sensor demonstrated a low limit of detection of 50 fg mL-1 with an extensive linear range of detection from 50 fg mL-1 to 0.1 μg mL-1.

Conclusion:

Fabricated immunosensor represented high stability, repeatability, specificity and resistance to most common interferences as well as great potential to analyse the real sample.

Dendrimers as Soft Nanomaterials for Electrochemical Immunosensors

Electrochemical immunosensors are antibody-based affinity biosensors with a high impact on clinical, environmental, food, and pharmaceutical analysis. In general, the analytical performance of these devices is critically determined by the materials and reagents used for their construction, signal production and amplification. Dendrimers are monodisperse and highly branched polymers with three-dimensional structures widely employed as “soft” nanomaterials in electrochemical immunosensor technology. This review provides an overview on the state-of-the-art in dendrimer-based electrochemical immunosensors, focusing on those using polyamidoamine and poly (propylene imine) dendrimers. Special emphasis is given to the most original methods recently reported for the construction of immunosensor architectures incorporating dendrimers, as well as to novel sensing approaches based on dendrimer-assisted signal enhancement strategies.

A Label-free Cardiac Troponin T Electrochemiluminescence Immunosensor Enhanced by Graphene Nanoplatelets

In this study, a direct and label-free immunosensor was designed and constructed by modifying the screen-printed electrode with graphene nanoplatelets (GNPs) for the detection of the cardiac troponin T (cTnT). Firstly, GNPs were drop-casted onto carbon working electrode. Monoclonal cTnT antibodies were then immobilized on the GNPs via physical adsorption; finally, BSA was introduced to block non-specific binding sites. The detection of cTnT was performed using an electrochemiluminescence (ECL) technique with tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)₃]Cl₂) used as a luminophore and TPrA (tripropylamine) as a co-reactant. The ECL intensity was demonstrated to be directly proportional to the cTnT concentration where a linear range from 100 pg mL^-1 to 5 fg mL^-1 of the cTnT detection was established. An extremely low limit of detection was achieved to be 0.05 fg mL^-1 with an outstanding specificity. Additionally, this immunosensor showed excellent percentage recovery for real samples analyses in artificially spiked human serum.

Clinical validity of saliva and novel technology for cancer detection

Cancer, a local disease at an early stage, systemically evolves as it progresses by triggering alterations in surrounding microenvironment, disturbing immune surveillance and further disseminating its molecular contents into circulation. This pathogenic characteristic of cancer makes the use of biofluids such as blood/serum/plasma, urine, tear and cerebrospinal fluids credible surrogates harboring tumor tissue-derived molecular alterations for the detection of cancer. Most importantly, a number of recent reports have credentialed the clinical validity of saliva for the detection of systemic diseases including cancers. In this review, we discussed the validity of saliva as credible biofluid and clinical sample type for the detection of cancers. We have presented the molecular constituents of saliva that could mirror the systemic status of our body and recent findings of salivaomics associated with cancers. Recently, liquid biopsy to detect cancer-derived circulating tumor DNA has emerged as a credible cancer-detection tool with potential benefits in screening, diagnosis and also risk management of cancers. We have further presented the clinical validity of saliva for liquid biopsy of cancers and a new technology platform based on electrochemical detection of cancer-derived ctDNA in saliva with superior sensitivity and point-of-care potential. The clinical utilities of saliva for the detection of cancers have been evidenced, but biological underpinning on the existence of molecular signatures of cancer-origin in saliva, such as via exosomal distribution, should be addressed in detail.

Food Safety Analysis Using Electrochemical Biosensors

Rapid and precise analytical tools are essential for monitoring food safety and screening of any undesirable contaminants, allergens, or pathogens, which may cause significant health risks upon consumption. Substantial developments in analytical techniques have empowered the analyses and quantitation of these contaminants. However, conventional techniques are limited by delayed analysis times, expensive and laborious sample preparation, and the necessity for highly-trained workers. Therefore, prompt advances in electrochemical biosensors have supported significant gains in quantitative detection and screening of food contaminants and showed incredible potential as a means of defying such limitations. Apart from indicating high specificity towards the target analytes, these biosensors have also addressed the challenge of food industry by providing high analytical accuracy within complex food matrices. Here, we discuss some of the recent advances in this area and analyze the role and contributions made by electrochemical biosensors in the food industry. This article also reviews the key challenges we believe biosensors need to overcome to become the industry standard.

Portable Nanofiber-Light Addressable Potentiometric Sensor for Rapid Escherichia coli Detection in Orange Juice

The growing need to prevent pathogen outbreaks is irrefutable in the case of the food industry. Early detection in products, especially beverages, contaminated with bacterial strains is vital to avoid infected foods from reaching the consumer. If E. coli is pesent in such foods, it can cause infections. It can also be an indicator of the existence of other harmful coliforms. In this study, we have investigated the detection of Escherichia coli ( E. coli) in orange juice using a portable nanofiber-light addressable potentiometric sensor (NF-LAPS). We have chosen electrospun pH-sensitive poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) hydrogel NFs as the sensitive layer. The successful detection of E. coli was reported with the NF-LAPS in less than 1 h. The limit of detection (LOD) measured in the sensor is found to be10² CFU/mL. We have confirmed the selectivity of the biosensor toward E. coli by examining the response of the NF-LAPS against Salmonella typhimurium ( S. typhi), also commonly found in orange juice. Despite the complex nature of orange juice, the response of the biosensor is in no way affected while orange juice is tested as is.

Sensors Based on Bio and Biomimetic Receptors in Medical Diagnostic, Environment, and Food Analysis

Analytical chemistry is now developing mainly in two areas: automation and the creation of complexes that allow, on the one hand, for simultaneously analyzing a large number of samples without the participation of an operator, and on the other, the development of portable miniature devices for personalized medicine and the monitoring of a human habitat. The sensor devices, the great majority of which are biosensors and chemical sensors, perform the role of the latter. That last line is considered in the proposed review. Attention is paid to transducers, receptors, techniques of immobilization of the receptor layer on the transducer surface, processes of signal generation and detection, and methods for increasing sensitivity and accuracy. The features of sensors based on synthetic receptors and additional components (aptamers, molecular imprinted polymers, biomimetics) are discussed. Examples of bio- and chemical sensors' application are given. Miniaturization paths, new power supply means, and wearable and printed sensors are described. Progress in this area opens a revolutionary era in the development of methods of on-site and in-situ monitoring, that is, paving the way from the "test-tube to the smartphone".

Ultracompact Microwatt CMOS Current Readout With Picoampere Noise and Kilohertz Bandwidth for Biosensor Arrays

High-density on-chip electrochemical biosensor arrays are advancing toward a crucial role in health monitoring and development of new medicines and medical treatments. Nanopore and ion channel based sensors especially have great potential but present demanding resolution/speed/power/area requirements on instrumentation circuits. This paper presents a pixel-level current readout circuit and new group-cluster architecture to address the circuit challenges in high-performance biosensor arrays. Fabricated in 0.5 μm CMOS, this electrochemical voltammetry circuit achieves 7.2 pA_rms noise in an 11.5-kHz bandwidth and only consumes 21-μ W power and 0.06 mm² area per readout channel. Cyclic voltammetry experiments in a potassium ferricyanide solution and patch-clamp whole-cell experiments were performed to validate the circuit's feasibility for electrochemical biosensor applications.

Fabrication of a new biosensor based on a Sn doped ceria nanoparticle modified glassy carbon paste electrode for the selective determination of the anticancer drug dacarbazine in pharmaceuticals

A new tin doped ceria nanoparticle modified glassy carbon paste electrode (Sn–CeO₂NPs/GCPE) was fabricated for the determination of the anticancer drug dacarbazine (DTIC).

DEP-On-Go for Simultaneous Sensing of Multiple Heavy Metals Pollutants in Environmental Samples

We describe a simple and affordable “Disposable electrode printed (DEP)-On-Go” sensing platform for the rapid on-site monitoring of trace heavy metal pollutants in environmental samples for early warning by developing a mobile electrochemical device composed of palm-sized potentiostat and disposable unmodified screen-printed electrode chips. We present the analytical performance of our device for the sensitive detection of major heavy metal ions, namely, mercury, cadmium, lead, arsenic, zinc, and copper with detection limits of 1.5, 2.6, 4.0, 5.0, 14.4, and, 15.5 μg·L⁻¹, respectively. Importantly, the utility of this device is extended to detect multiple heavy metals simultaneously with well-defined voltammograms and similar sensitivity. Finally, “DEP-On-Go” was successfully applied to detect heavy metals in real environmental samples from groundwater, tap water, house dust, soil, and industry-processed rice and noodle foods. We evaluated the efficiency of this system with a linear correlation through inductively coupled plasma mass spectrometry, and the results suggested that this system can be reliable for on-site screening purposes. On-field applications using real samples of groundwater for drinking in the northern parts of India support the easy-to-detect, low-cost (<1 USD), rapid (within 5 min), and reliable detection limit (ppb levels) performance of our device for the on-site detection and monitoring of multiple heavy metals in resource-limited settings.

Metallacarboranes as tunable redox potential electrochemical indicators for screening of gene mutation

The substitution of hydrogen with chlorine in the metallacarborane [3,3-Fe(1,2-closo-C2B9H11)2]- cluster modulates the formal potential of the Fe3+/Fe2+ redox couple, shifting it to a more positive value. Hence, very similar redox probes with a wide range of formal potentials, ranging from negative to positive values, are available. Thus, we have achieved the synthesis and studied the electrochemical behaviour of the sodium salt of [3,3-Fe(8,9,12-Cl3-1,2-closo-C2B9H8)2]- in aqueous media. This strategy allows tuning of the redox potential of the [3,3-Fe(1,2-closo-C2B9H11)2]- framework with a minor change in its shape and dimensions. We also describe the interaction of the prepared [3,3-Fe(8,9,12-Cl3-1,2-closo-C2B9H8)2]- and the pristine [3,3-Fe(1,2-closo-C2B9H11)2]- with DNA. These studies have been carried out not only with DNA in solution but also with DNA immobilized on screen-printed gold electrodes. The results obtained point to a strong interaction between the metallacarboranes and DNA, to a different extent with single stranded DNA (ssDNA) compared to double stranded DNA (dsDNA). This property makes them selective and wide-ranging potential electrochemical indicators of hybridization. The suitability of these new redox indicators for selective DNA biosensor development has been probed by the direct detection of two different mutations associated with cystic fibrosis in PCR amplicons extracted from blood cells.

A label free electrochemical immunosensor for sensitive detection of porcine serum albumin as a marker for pork adulteration in raw meat

A label free electrochemical immunosensor for sensitive detection of porcine serum albumin (PSA) is reported in this work. The immunosensor was constructed by first electrochemically reducing 4-carboxyphenyl diazonium salt, which had been electrochemically generated in situ, to a stable 4-carboxyphenyl layer on carbon nanofiber-modified screen printed electrode. Antibodies were covalently attached onto the electrode using carbodiimide chemistry between the carboxylic groups of the 4-carboxyphenyl layer and amine groups of the antibody. Using the strong affinities of serum albumins towards anions, the increase in cathodic peak current in anionic redox probe after immunocomplex formation with antibodies was used for PSA detection. The reported immunosensor demonstrated a linear range from 0.5 to 500pg/mL for the measurement of PSA with detection limit of 0.5pg/mL in buffer solution. Cross-reactivity studies have shown excellent specificity with satisfactory recovery of PSA in fresh meat samples without the need of sample dilution.

Emerging Loop-Mediated Isothermal Amplification-Based Microchip and Microdevice Technologies for Nucleic Acid Detection

Rapid, sensitive, and selective pathogen detection is of paramount importance in infectious disease diagnosis and treatment monitoring. Currently available diagnostic assays based on polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) are time-consuming, complex, and relatively expensive, thus limiting their utility in resource-limited settings. Loop-mediated isothermal amplification (LAMP) technique has been used extensively in the development of rapid and sensitive diagnostic assays for pathogen detection and nucleic acid analysis and hold great promise for revolutionizing point-of-care molecular diagnostics. Here, we review novel LAMP-based lab-on-a-chip (LOC) diagnostic assays developed for pathogen detection over the past several years. We review various LOC platforms based on their design strategies for pathogen detection and discuss LAMP-based platforms still in development and already in the commercial pipeline. This review is intended as a guide to the use of LAMP techniques in LOC platforms for molecular diagnostics and genomic amplifications.

Paper-based rapid detection of pork and chicken using LAMP–magnetic bead aggregates

Magnetic beads (MBs) have been widely used for DNA quantification.

Electrochemical immunosensors and their recent nanomaterial-based signal amplification strategies: a review

In recent years, tremendous advances have been made in biosensors based on nanoscale electrochemical immunosensors for use in the fields of agriculture, food safety, biomedicine, quality control, and environmental and industrial monitoring.

Biosensors Incorporating Bimetallic Nanoparticles

This article presents a review of electrochemical bio-sensing for target analytes based on the use of electrocatalytic bimetallic nanoparticles (NPs), which can improve both the sensitivity and selectivity of biosensors. The review moves quickly from an introduction to the field of bio-sensing, to the importance of biosensors in today's society, the nature of the electrochemical methods employed and the attendant problems encountered. The role of electrocatalysts is introduced with reference to the three generations of biosensors. The contributions made by previous workers using bimetallic constructs, grouped by target analyte, are then examined in detail; following which, the synthesis and characterization of the catalytic particles is examined prior to a summary of the current state of endeavor. Finally, some perspectives for the future of bimetallic NPs in biosensors are given.

A carbon nanofiber-based label free immunosensor for high sensitive detection of recombinant bovine somatotropin

A carbon nanofiber-based label free electrochemical immunosensor for sensitive detection of recombinant bovine somatotropin (rbST) was developed. In this immunosensor design, a mild site-directed antibody immobilization via interaction of boronic acid and oligosaccharide moiety found on Fc region of an antibody was performed to preserve the biological activity of antibody and improve the sensor's sensitivity. Electrochemical characterization of the immunosensor fabrication was carried out by differential pulse voltammetry (DPV) in Fe(CN)6(3-)/Fe(CN)6(4-) probe. A comparison study between different transducer platforms showed carbon nanofiber gave higher current signal response than single-walled carbon nanotube. In this work, calibration curve was obtained from the decrease of DPV peak current of Fe(CN)6(3-)/Fe(CN)6(4-) after immunocomplexed was formed. A linear relationship between DPV current change signal response and rbST concentrations from 1 pg/mL to 10 ng/mL (correlation coefficient of 0.9721) was achieved with detection limit of 1 pg/mL. Our developed immunosensor demonstrated high selectivity in cross-reactivity studies and a good percentage recovery in spiked bovine serum sample.

Optical sensor arrays for chemical sensing: the optoelectronic nose

A comprehensive review is presented on the development and state of the art of colorimetric and fluorometric sensor arrays. Optical arrays based on chemoresponsive colorants (dyes and nanoporous pigments) probe the chemical reactivity of analytes, rather than their physical properties. This provides a high dimensionality to chemical sensing that permits high sensitivity (often down to ppb levels), impressive discrimination among very similar analytes and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, both in the gas and liquid phases.

A highly sensitive gold nanoparticle bioprobe based electrochemical immunosensor using screen printed graphene biochip

This study describes a highly sensitive electrochemical immunosensor for the detection of human chorionic gonadotropin (hCG) that uses gold nanoparticles (AuNP) as the electrochemical label and graphene as electrode material.