Electrochemical Biosensors - Sensor Principles and Architectures

An impedance labeling free electrochemical aptamer sensor based on tetrahedral DNA nanostructures for doxorubicin determination

Based on the electrochemical impedance method, a marker-free biosensor with aptamer as a biometric element was developed for the determination of doxorubicin (DOX). By combining aptamer with rigid tetrahedral DNA nanostructures (TDNs) and fixing them on the surface of gold electrode (GE) as biometric elements, the density and directivity of surface nanoprobes improved, and DOX was captured with high sensitivity and specificity. DOX was captured by immobilized aptamers on the GE, which inhibited electron transfer between the GE and [Fe(CN)6]3-/4- in solution, resulting in a change in electrochemical impedance. When the DOX concentration was between 10.0 and 100.0 nM, the aptasensor showed a linear relationship with charge transfer resistance, the relative standard deviation (RSD) ranged from 3.6 to 5.9%, and the detection limit (LOD) was 3.0 nM. This technique offered a successful performance for the determination of the target analyte in serum samples with recovery in the range 97.0 to 99.6% and RSD ranged from 4.8 to 6.5%. This method displayed the advantages of fast response speed, good selectivity, and simple sensor structure and showed potential application in therapeutic drug monitoring.

Electrochemical DNA biosensors developed for the monitoring of biointeractions with drugs: a review

The interaction of drugs with DNA is important for the discovery of novel drug molecules and for understanding the therapeutic effects of drugs as well as the monitoring of side effects. For this reason, many studies have been carried out to investigate the interactions of drugs with nucleic acids. In recent years, a large number of studies have been performed to electrochemically detect drug-DNA interactions. The fast, sensitive, and accurate results of electrochemical techniques have resulted in a leading role for their implementation in this field. By means of electrochemical techniques, it is possible not only to demonstrate drug-DNA interactions but also to quantitatively analyze drugs. In this context, electrochemical biosensors for drug-DNA interactions have been examined under different headings including anticancer, antiviral, antibiotic, and central nervous system drugs as well as DNA-targeted drugs. An overview of the studies related to electrochemical DNA biosensors developed for the detection of drug-DNA interactions that were reported in the last two decades in the literature is presented herein along with their applications and they are discussed together with their future perspectives.

Application of biosensors in cancers, an overview

The deadliest disease in the world, cancer, kills many people every year. The early detection is the only hope for the survival of malignant cancer patients. As a result, in the preliminary stages of, the diagnosis of cancer biomarkers at the cellular level is critical for improving cancer patient survival rates. For decades, scientists have focused their efforts on the invention of biosensors. Biosensors, in addition to being employed in other practical scenarios, can essentially function as cost effective and highly efficient devices for this purpose. Traditional cancer screening procedures are expensive, time-consuming, and inconvenient for repeat screenings. Biomarker-based cancer diagnosis, on the other hand, is rising as one of the most potential tools for early detection, disease progression monitoring, and eventual cancer treatment. As Biosensor is an analytical device, it allows the selected analyte to bind to the biomolecules being studied (for example RNA, DNA, tissue, proteins, and cells). They can be divided based on the kind of biorecognition or transducer elements on the sensor. Most biosensor analyses necessitate the analyte being labeled with a specific marker. In this review article, the application of distinct variants of biosensors against cancer has been described.

Application of Localized Surface Plasmon Resonance of Conjugated Gold Nanoparticles in Spectral Diagnosis of SARS-CoV-2: A Numerical Study

Severe respiratory syndrome COVID-19 (SARS-CoV-2) outbreak has became the most important global health issue, and simultaneous efforts to fast and low-cost diagnosis of this virus were performed by researchers. One of the most usual tests was colorimetric methods based on the change of color of gold nanoparticles in the presence of viral antibodies, antigens, and other biological agents. This spectral change can be due to the aggregation of the particles or the shift of localized surface plasmon resonance due to the electrical interactions of surface agents. It is known that surface agents could easily shift the absorption peak of metallic nanocolloids which is attributed to the localized surface plasmon resonance. Experimental diagnosis assays for colorimetric detection of SARS-CoV-2 using Au NPs were reviewed, and the shift of absorption peak was studied from the viewpoint of numerical analysis. Using the numerical method, the refractive index and real and imaginary parts of the effective relative permittivity of the viral biological shell around Au NPs were obtained. This model gives a quantitative description of colorimetric assays of the detection of SARS-CoV-2 using Au NPs.

Electrochemical and Bioelectrochemical Sensing Platforms for Diagnostics of COVID-19

Rapid transmission and high mortality rates caused by the SARS-CoV-2 virus showed that the best way to fight against the pandemic was through rapid, accurate diagnosis in parallel with vaccination. In this context, several research groups around the world have endeavored to develop new diagnostic methods due to the disadvantages of the gold standard method, reverse transcriptase polymerase chain reaction (RT-PCR), in terms of cost and time consumption. Electrochemical and bioelectrochemical platforms have been important tools for overcoming the limitations of conventional diagnostic platforms, including accuracy, accessibility, portability, and response time. In this review, we report on several electrochemical sensors and biosensors developed for SARS-CoV-2 detection, presenting the concepts, fabrication, advantages, and disadvantages of the different approaches. The focus is devoted to highlighting the recent progress of electrochemical devices developed as next-generation field-deployable analytical tools as well as guiding future researchers in the manufacture of devices for disease diagnosis.

Polyaniline-based electrochemical immunosensor for the determination of antibodies against SARS-CoV-2 spike protein

In this work, we report an impedimetric system for the detection of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Spike protein. The sensing platform is based on recombinant Spike protein (SCoV2-rS) immobilized on the phytic acid doped polyaniline films (PANI-PA). The affinity interaction between immobilized SCoV2-rS protein and antibodies in the physiological range of concentrations was registered by electrochemical impedance spectroscopy. Analytical parameters of the sensing platform were tuned by the variation of electropolymerization times during the synthesis of PANI-PA films. The lowest limit of detection and quantification were obtained for electropolymerization time of 20 min and equalled 8.00 ± 0.20 nM and 23.93 ± 0.60 nM with an equilibrium dissociation constant of 3 nM. The presented sensing system is label-free and suitable for the direct detection of antibodies against SARS-CoV-2 in real patient serum samples after coronavirus disease 2019 and/or vaccination.

Review of electrochemical and optical biosensors for testosterone measurement

Testosterone is an anabolic steroid and a major sex hormone in males. It plays vital roles, including developing the testis, penis, and prostate, increasing muscle and bone, and sperm production. In both men and women, testosterone levels should be in normal ranges. Besides, testosterone and its analogs are major global contributors to doping in sport. Due to the importance of testosterone testing, novel, accurate biosensors have been developed. This review summarizes the various methods for testosterone measurement. Also, recent optical and electrochemical approaches for the detection of testosterone and its analogs have been discussed.

Advancement in COVID-19 detection using nanomaterial-based biosensors

Coronavirus disease 2019 (COVID-19) pandemic has exemplified how viral growth and transmission are a significant threat to global biosecurity. The early detection and treatment of viral infections is the top priority to prevent fresh waves and control the pandemic. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified through several conventional molecular methodologies that are time-consuming and require high-skill labor, apparatus, and biochemical reagents but have a low detection accuracy. These bottlenecks hamper conventional methods from resolving the COVID-19 emergency. However, interdisciplinary advances in nanomaterials and biotechnology, such as nanomaterials-based biosensors, have opened new avenues for rapid and ultrasensitive detection of pathogens in the field of healthcare. Many updated nanomaterials-based biosensors, namely electrochemical, field-effect transistor, plasmonic, and colorimetric biosensors, employ nucleic acid and antigen-antibody interactions for SARS-CoV-2 detection in a highly efficient, reliable, sensitive, and rapid manner. This systematic review summarizes the mechanisms and characteristics of nanomaterials-based biosensors for SARS-CoV-2 detection. Moreover, continuing challenges and emerging trends in biosensor development are also discussed.

A low-frequency acceleration sensor inspired by saccule in human vestibule

A human vestibular system is a group of devices in the inner ear that govern the balancing movement of the head, in which the saccule is responsible for sensing gravity accelerations. Imitating the sensing principle and structure of the Sensory Hair (SH) cell in the saccule, a Bionic Sensory Hair (BSH) was developed, and 9 BSH arrays were arranged in the bionic macular at the bottom of the spherical shell to prepare a Bionic Saccule (BS). Based on the piezoelectric equation, the electromechanical theoretical models of the BSH cantilever and BS were deduced. They were subjected to impact oscillations using an exciter, and their output charges were analyzed to check their sensing ability. The results showed that BSH could sense its bending deflection, and the BS could sense its position change in the sagittal plane and in space. They exhibited a sensitivity of 1.6104 Pc s²/m and a fast response and similar sensing principles and low resonance frequency to those of the human saccule. The BS is expected to be used in the field of robotics and clinical disease diagnosis as a part of the artificial vestibular system in the future.

Advances in the Translation of Electrochemical Hydrogel-Based Sensors

Novel biomaterials for bio- and chemical sensing applications have gained considerable traction in the diagnostic community with rising trends of using biocompatible and lowly cytotoxic material. Hydrogel-based electrochemical sensors have become a promising candidate for their swellable, nano-/microporous, and aqueous 3D structures capable of immobilizing catalytic enzymes, electroactive species, whole cells, and complex tissue models, while maintaining tunable mechanical properties in wearable and implantable applications. With advances in highly controllable fabrication and processability of these novel biomaterials, the possibility of bio-nanocomposite hydrogel-based electrochemical sensing presents a paradigm shift in the development of biocompatible, "smart," and sensitive health monitoring point-of-care devices. Here, recent advances in electrochemical hydrogels for the detection of biomarkers in vitro, in situ, and in vivo are briefly reviewed to demonstrate their applicability in ideal conditions, in complex cellular environments, and in live animal models, respectively, to provide a comprehensive assessment of whether these biomaterials are ready for point-of-care translation and biointegration. Sensors based on conductive and nonconductive polymers are presented, with highlights of nano-/microstructured electrodes that provide enhanced sensitivity and selectivity in biocompatible matrices. An outlook on current challenges that shall be addressed for the realization of truly continuous real-time sensing platforms is also presented.

A Short Review Comparing Carbon-Based Electrochemical Platforms With Other Materials For Biosensing SARS-Cov-2

Due to the 2019 SARS-CoV-2 outbreak, low-cost, fast, and user-friendly diagnostic kits for biosensing SARS-CoV-2 in real samples employing multiple working electrodes are in high demand. Choosing SARS-CoV-2 detecting electrodes is difficult because each has advantages and limitations. Carbon-based electrochemical sensing applications have attracted attention from the electrochemical sensing community because carbon and carbon-based materials have been a godsend for testing utilizing an electrochemical platform. Carbon working electrode electrochemical platforms are cost-effective and fast. Covid-sensors use carbon-based materials because they can be easily changed (with inorganic and organic functionalities), have quick response kinetics, and are chemically resistant. Covid-19 sensing materials include graphene and graphite. This review explains how carbon materials have been employed in N and S protein electrochemical detection. Here, we discussed a carbon-based technology for SARS-CoV-2 biosensing. We've compared carbon-based electrochemical sensing to different electrodes.

A Low-Cost Handheld Impedimetric Biosensing System for Rapid Diagnostics of SARS-CoV-2 Infections

Current laboratory diagnostic approaches for virus detection give reliable results, but they require a lengthy procedure, trained personnel, and expensive equipment and reagents; hence, they are not a suitable choice for home monitoring purposes. This paper addresses this challenge by developing a portable impedimetric biosensing system for the identification of COVID-19 patients. This sensing system has two main parts: a throwaway two-working electrode (2-WE) strip and a novel read-out circuit, specifically designed for simultaneous signal acquisition from both working electrodes. Highly reliable electrochemical signal tracking from multiplex immunosensors provides a potential for flexible and portable multi-biomarker detection. The electrodes' surfaces were functionalized with SARS-CoV-2 Nucleocapsid Antibody enabling the selective detection of Nucleocapsid protein (N-protein) along with self-validation in the clinical nasopharyngeal swab specimens. The proposed programmable highly sensitive impedance read-out system allows for a wide dynamic detection range, which makes the sensor capable of detecting N-protein concentrations between 0.116 and 10,000 pg/mL. This lightweight and economical read-out arrangement is an ideal prospect for being mass-produced, especially during urgent pandemic situations. Also, such an impedimetric sensing platform has the potential to be redesigned for targeting not only other infectious diseases but also other critical disorders.

Novel Electrochemical Sensing of Catechins in Raw Green Tea Extract via a Trimetallic Zeolitic Imidazolate Fibrous Framework

Human health-related issues are increasing in day to day life because of the modern and unhygienic food lifestyles. In recent times, green tea (GT) gains more attention due to its numerous health benefits. It contains more biologically active compounds that improve mental health, increase metabolism, reduce cancer risks, and serve as an anti-aging agent for the brain. As it is globally consumed, the evaluation of the compounds present in it is very important. Hence, an attempt has been performed to evaluate these components in GT by using a cobalt nickel iron-based trimetallic zeolitic imidazolate framework as microfibers (CoNiFe-ZIF-MFs) synthesized via an electrospinning technique. Interestingly, the synthesized CoNiFe-ZIF-MFs catalyst simultaneously detects three major catechin (CT) groups, namely, epigallocatechin-3-gallate (EGCG), epicatechin (EC), and epicatechingallate (ECG). Further, the square wave voltammetry findings showed that there is a wide linear range of 50 ng to 1 mg for all the three CTs with LODs 45, 8, and 4 ng for EGCG, EC, and ECG, respectively. These results confirm the excellent sensing behavior of the composite toward GT extracts, proposing its practical utility in real-time compound analysis in food sectors. Other results like stability and reproducibility also promote its usage in the biomedical field. This study mainly focuses on the direct sensing of CTs present in GT without spiking any commercially purchased sample, and the sensing was performed simultaneously for all the three analytes; thus, this work gains novelty from the existing ones.

Microfluidic Chip for the Electrochemical Detection of MicroRNAs: Methylene Blue Increasing the Specificity of the Biosensor

MicroRNAs (miRNAs) are biomarkers involved in biological processes that are released by cells and found in biological fluids such as blood. The development of nucleic acid-based biosensors has significantly increased in the past 10 years because the detection of such nucleic acids can easily be applied in the field of early diagnosis. These biosensors need to be sensitive, specific, and fast in order to be effective. This work introduces a newly-built electrochemical biosensor that enables a fast detection in 30 min and, as a result of its integration in microfluidics, presents a limit of detection as low as 1 aM. The litterature concerning the specificity of electrochemical biosensors includes several studies that report one base-mismatch, with the base-mismatch located in the middle of the strand. We report an electrochemical nucleic acid biosensor integrated into a microfluidic chip, allowing for a one-base-mismatch specificity independently from the location of the mismatch in the strand. This specificity was improved using a solution of methylene blue, making it possible to discriminate a partial hybridization from a complete and complementary hybridization.

Detection of Amyloid-β(1–42) Aggregation With a Nanostructured Electrochemical Sandwich Immunoassay Biosensor

Amyloid-β(1–42) [Aβ(1–42)] oligomer accumulations are associated with physiologic alterations in the brains of individuals with Alzheimer’s disease. In this study, we demonstrate that a nanostructured gold electrode with deposited gold nanoparticles, induced via electrochemical impedance spectroscopy (EIS), may be used as an Aβ(1–42) conformation biosensor for the detection of Alzheimer’s disease. Monoclonal antibodies (12F4) were immobilized on self-assembled monolayers of the electrochemical sandwich immunoassay biosensor to capture Aβ(1–42) monomers and oligomers. Western blot and fluorescence microscopy analyses were performed to confirm the presence of Aβ(1–42) monomers and oligomers. EIS analysis with an equivalent circuit model was used to determine the concentrations of different Aβ(1–42) conformations in this study. We identified conformations of Aβ(1–42) monomers and Aβ(1–42) oligomers using probe antibodies (12F4) by employing EIS. RAβ(1−42) indicates the sum resistance of impedance measured during Aβ(1–42) immobilization. ΔR12F4 refers to the concentration of probe antibody (12F4) binding with Aβ(1–42). The concentration of Aβ(1–42) oligomer was defined as the percentage of Aβ(1–42) aggregation R12F4/RAβ(1−42). The experimental results show that the biosensor has high selectivity to differentiate Aβ(1–40) and Aβ(1–42) monomers and Aβ(1–42) oligomers and that it can detect Aβ(1–42) oligomer accurately. The linear detection range for Aβ(1–42) oligomers was between 10 pg/ml and 100 ng/ml. The limit of detection was estimated to be 113 fg/ml.

New insights for integration of nano particle with microfluidic systems for sensor applications

A biosensor is a compact device, which utilizes biological derived recognition component, immobilized on a transducer to analyze an analyte. Nanoparticles with their unique chemical and physical properties are versatile in their applications to develop as sensors. Different nanoparticles play different roles in the sensing systems like metal and metal oxide nanoparticles. The application of Gold, Silver and Copper nanoparticles will be discussed in brief. The nanoparticles typically function as substrates for immobilization of biomolecules, as catalytic agent, electron transfer agent between electrode surface and the biomolecules, and as reactants. Microfluidic deals with manipulating very small volumes of fluids (micro and nanoliters). This miniaturized platform enhances control of flow conditions and mixing rate of fluids. The microfluidics improves the sensitivity of the analysis, and reduces the volumes of sample and reagent in the analysis. The review specifically aims at representing microfluidics-based sensors and nanoparticle based sensors. This review will also focus on probable merger of these two fields to take advantage of both the fields and this will help in pushing the boundaries of these fields further more.

Zwitterionic Polymer Electroplating Facilitates the Preparation of Electrode Surfaces for Biosensing

Surface chemistry critically affects the diagnostic performance of biosensors. An ideal sensor surface should be resistant to nonspecific protein adsorption, yet be conducive to analytical responses. Here a new polymeric material, zwitterionic polypyrrole (ZiPPy), is reported to produce optimal surface condition for biosensing electrodes. ZiPPy combines two unique advantages: the zwitterionic function that efficiently hydrates electrode surface, hindering nonspecific binding of hydrophobic proteins; and the pyrrole backbone, which enables rapid (<7 min), controlled deposition of ZiPPy through electropolymerization. ZiPPy-coated electrodes show lower electrochemical impedance and less nonspecific protein adsorption (low fouling), outperforming bare and polypyrrole-coated electrodes. Moreover, affinity ligands for target biomarkers can be immobilized together with ZiPPy in a single-step electropolymerization. ZiPPy-coated electrodes are developed with specificity for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The prepared sensor detects SARS-CoV-2 antibodies in human saliva down to 50 ng mL^-1 , without the need for sample purification or secondary labeling.

Biosensors and Point-of-Care Devices for Bacterial Detection: Rapid Diagnostics Informing Antibiotic Therapy

With an exponential rise in antimicrobial resistance and stagnant antibiotic development pipeline, there is, more than ever, a crucial need to optimize current infection therapy approaches. One of the most important stages in this process requires rapid and effective identification of pathogenic bacteria responsible for diseases. Current gold standard techniques of bacterial detection include culture methods, polymerase chain reactions, and immunoassays. However, their use is fraught with downsides with high turnaround time and low accuracy being the most prominent. This imposes great limitations on their eventual application as point-of-care devices. Over time, innovative detection techniques have been proposed and developed to curb these drawbacks. In this review, a systematic summary of a range of biosensing platforms is provided with a strong focus on technologies conferring high detection sensitivity and specificity. A thorough analysis is performed and the benefits and drawbacks of each type of biosensor are highlighted, the factors influencing their potential as point-of-care devices are discussed, and the authors' insights for their translation from proof-of-concept systems into commercial medical devices are provided.

Biomedical IoT: Enabling Technologies, Architectural Elements, Challenges, and Future Directions

This paper provides a comprehensive literature review of various technologies and protocols used for medical Internet of Things (IoT) with a thorough examination of current enabling technologies, use cases, applications, and challenges. Despite recent advances, medical IoT is still not considered a routine practice. Due to regulation, ethical, and technological challenges of biomedical hardware, the growth of medical IoT is inhibited. Medical IoT continues to advance in terms of biomedical hardware, and monitoring figures like vital signs, temperature, electrical signals, oxygen levels, cancer indicators, glucose levels, and other bodily levels. In the upcoming years, medical IoT is expected replace old healthcare systems. In comparison to other survey papers on this topic, our paper provides a thorough summary of the most relevant protocols and technologies specifically for medical IoT as well as the challenges. Our paper also contains several proposed frameworks and use cases of medical IoT in hospital settings as well as a comprehensive overview of previous architectures of IoT regarding the strengths and weaknesses. We hope to enable researchers of multiple disciplines, developers, and biomedical engineers to quickly become knowledgeable on how various technologies cooperate and how current frameworks can be modified for new use cases, thus inspiring more growth in medical IoT.

Recent advances in the detection of interferon-gamma as a TB biomarker

Tuberculosis (TB) is one of the main infectious diseases worldwide and accounts for many deaths. It is caused by Mycobacterium tuberculosis usually affecting the lungs of patients. Early diagnosis and treatment are essential to control the TB epidemic. Interferon-gamma (IFN-γ) is a cytokine that plays a part in the body’s immune response when fighting infection. Current conventional antibody-based TB sensing techniques which are commonly used include enzyme-linked immunosorbent assay (ELISA) and interferon-gamma release assays (IGRAs). However, these methods have major drawbacks, such as being time-consuming, low sensitivity, and inability to distinguish between the different stages of the TB disease. Several electrochemical biosensor systems have been reported for the detection of interferon-gamma with high sensitivity and selectivity. Microfluidic techniques coupled with multiplex analysis in regular format and as lab-on-chip platforms have also been reported for the detection of IFN-γ. This article is a review of the techniques for detection of interferon-gamma as a TB disease biomarker. The objective is to provide a concise assessment of the available IFN-γ detection techniques (including conventional assays, biosensors, microfluidics, and multiplex analysis) and their ability to distinguish the different stages of the TB disease.

Trending Technology of Glucose Monitoring during COVID-19 Pandemic: Challenges in Personalized Healthcare

The COVID-19 pandemic has continued to spread rapidly, and patients with diabetes are at risk of experiencing rapid progression and poor prognosis for appropriate treatment. Continuous glucose monitoring (CGM), which includes accurately tracking fluctuations in glucose levels without raising the risk of coronavirus exposure, becomes an important strategy for the self-management of diabetes during this pandemic, efficiently contributing to the diabetes care and the fight against COVID-19. Despite being less accurate than direct blood glucose monitoring, wearable noninvasive systems can encourage patient adherence by guaranteeing reliable results through high correlation between blood glucose levels and glucose concentrations in various other biofluids. This review highlights the trending technologies of glucose sensors during the ongoing COVID-19 pandemic (2019-2020) that have been developed to make a significant contribution to effective management of diabetes and prevention of coronavirus spread, from off-body systems to wearable on-body CGM devices, including nanostructure and sensor performance in various biofluids. The advantages and disadvantages of various human biofluids for use in glucose sensors are also discussed. Furthermore, the challenges faced by wearable CGM sensors with respect to personalized healthcare during and after the pandemic are deliberated to emphasize the potential future directions of CGM devices for diabetes management.

Enhancing affinity-based electroanalytical biosensors by integrated AC electrokinetic enrichment-A mini review

Biosensors play a central role in moving diagnostics to being on-site or decentralized. Affinity biosensor, an important category of biosensors, has important applications in clinical diagnosis, pharmaceuticals, immunology, and other fields. Affinity biosensors rely on specific binding between target analytes and biological ligands such as antibodies, nucleic acids, or other receptors to generate measurable signals. Oftentimes the target analytes in practical samples are of low abundance in a complex matrix. Traditional affinity biosensors mainly rely on random diffusion of analytes in solution to conjugate with biorecognition elements on the sensor surface of electrodes. The process may take hours or even days, which is not conducive to rapid and sensitive detection of biosensors. Therefore, it is strongly desired to incorporate an enrichment mechanism for target analytes into biosensor-based detection. AC electrokinetic (ACEK) effect can realize rapid enrichment of analytes by application of AC electric fields, which holds great promise for achieving high sensitivity, low detection limit, and rapid turnaround. This article reviews the studies of affinity biosensors integrated with ACEK enrichment in the past decade, and summarizes the latest detection methods, detection devices and applications, hoping to provide some insights and references for researchers in related fields.

Nanomaterial-assisted determination of osteosarcoma by antibody-osteopontin-aptamer sandwich ELISA

Immobilization and detection of small molecules is one of the challenging tasks in any given sensing system as the dissociation equilibrium constant is higher. Generating a right immobilization system with small molecules is mandatory for developing the drug-discovery process and disease identification. Immobilizing smaller probes on the ELISA plate is challenging because of its less adsorption on the polystyrene (PS) substrate. This research work developed an iron nanomaterial-based linker to attach osteopontin-specific aptamer on PS substrate. Iron oxide nanoparticle was attached on PS plate through amine modification and then antibody was attached by COOH reaction. On the osteopontin-modified plate, osteosarcoma biomarker of osteopontin was identified by its specific antibody and aptamer sandwich with the detection limit of 1 nM. Further, biofouling experiments with other molecules, such as lysozyme, and complementary aptamer failed to show the ELISA adsorption signal, indicating the iron oxide nanoparticle-modified PS plate specifically recognizes osteopontin. This research work effectively identifies the lesser abundance of osteopontin and helps to diagnose the osteosarcoma-related problems.

Ultrasensitive and Selective Impedimetric Determination of Prostate Specific Membrane Antigen Based on Di-Succinimide Functionalized Polythiophene Covered Cost-Effective Indium Tin Oxide

A new and ultrasensitive impedimetric biosensor fabricated by using conjugated di-succinimide substituted polythiophene (P(ThidiSuc)) polymer modified indium tin oxide electrode is developed for the first time to detect the prostate specific membrane antigen (PSMA). The polymer P(Thi-diSuc) is synthesized by using a simple way and used in the fabrication of the proposed biosensor. The synthesized polymer contains di-succinimide groups, which offers covalent immobilization of PSMA specific antibodies. The developed strategy shortens the biosensor fabrication steps, because these active groups bind covalently to the amino ends of PSMA specific antibodies and this reaction does not require any crosslinking agent. Various characterization studies like impedimetric and voltammetric measurements, and morphological analyses are utilized to confirm the successful development of the biosensor. Under optimum conditions, the biosensing ability of the PSMA determination has a wide linear determination range from 0.015 to 14.4 pg mL^-1 , as well as a low limit of detection of 6.4 fg mL^-1 and a high sensitivity of 1.36 kohm pg^-1 mL cm^-2 . Furthermore, the proposed biosensor is able to measure the PSMA antigen in real human serums, which offers that it is a simple, low-cost, and sensitive tool with excellent potential for application in the quantification of PSMA.

Flex Printed Circuit Board Implemented Graphene-Based DNA Sensor for Detection of SARS-CoV-2

Since the COVID-19 outbreak was declared a pandemic by the World Health Organization (WHO) in March 2020, ongoing efforts have been made to develop sensitive diagnostic platforms. Detection of viral RNA provides the highest sensitivity and specificity for detection of early and asymptomatic infections. Thus, this work aimed at developing a label-free genosensor composed of graphene as a working electrode that could be embedded into a flex printed circuit board (FPCB) for the rapid, sensitive, amplification-free and label-free detection of SARS-CoV-2. To facilitate liquid handling and ease of use, the developed biosensor was embedded with a user-friendly reservoir chamber. As a proof-of-concept, detection of a synthetic DNA strand matching the sequence of ORF1ab was performed as a two-step strategy involving the immobilization of a biotinylated complementary sequence on a streptavidin-modified surface, followed by hybridization with the target sequence recorded by the differential pulse voltammetric (DPV) technique in the presence of a ferro/ferricyanide redox couple. The effective design of the sensing platform improved its selectivity and sensitivity and allowed DNA quantification ranging from 100 fg/mL to [Formula: see text]/mL. Combining the electrochemical technique with FPCB enabled rapid detection of the target sequence using a small volume of the sample (5-[Formula: see text]). We achieved a limit-of-detection of 100 fg/mL, whereas the predicted value was ~33 fg/mL, equivalent to approximately [Formula: see text] copies/mL and comparable to sensitivities provided by isothermal nucleic acid amplification tests. We believe that the developed approach proves the ability of an FPCB-implemented DNA sensor to act as a potentially simpler and more affordable diagnostic assay for viral infections in Point-Of-Care (POC) applications.

Synergizing Functional Nanomaterials with Aptamers Based on Electrochemical Strategies for Pesticide Detection: Current Status and Perspectives

Owing to the high toxicity and large-scale use of pesticides, it is imperative to develop selective, sensitive, portable, and convenient sensors for rapid monitoring of pesticide. Therefore, the electrochemical detection platform offers a promising analytical approach since it is easy to operate, economical, efficient, and user-friendly. Meanwhile, with advances in functional nanomaterials and aptamer selection technologies, numerous sensitivity-enhancement techniques alongside a widespread range of smart nanomaterials have been merged to construct novel aptamer probes to use in the biosensing field. Hence, this study intends to highlight recent development and promising applications on the functional nanomaterials with aptamers for pesticides detection based on electrochemical strategies. We also reviewed the current novel aptamer-functionalized microdevices for the portability of pesticides sensors. Furthermore, the major challenges and future prospects in this field are also discussed to provide ideas for further research.

Vitamins in wine: Which, what for, and how much?

Vitamins are essential compounds to yeasts, and notably in winemaking contexts. Vitamins are involved in numerous yeast metabolic pathways, including those of amino acids, fatty acids, and alcohols, which suggests their notable implication in fermentation courses, as well as in the development of aromatic compounds in wines. Although they are major components in the course of those microbial processes, their significance and impact have not been extensively studied in the context of winemaking and wine products, as most of the studies focusing on the subject in the past decades have relied on relatively insensitive and imprecise analytical methods. Therefore, this review provides an extensive overview of the current knowledge regarding the impacts of vitamins on grape must fermentations, wine-related yeast metabolisms, and requirements, as well as on the profile of wine sensory characteristics. We also highlight the methodologies and techniques developed over time to perform vitamin analysis in wines, and assess the importance of precisely defining the role played by vitamins in winemaking processes, to ensure finer control of the fermentation courses and product characteristics in a highly complex matrix.

Point-of-Care Diagnostics: Molecularly Imprinted Polymers and Nanomaterials for Enhanced Biosensor Selectivity and Transduction

Significant healthcare disparities resulting from personal wealth, circumstances of birth, education level, and more are internationally prevalent. As such, advances in biomedical science overwhelmingly benefit a minority of the global population. Point-of-Care Testing (POCT) can contribute to societal equilibrium by making medical diagnostics affordable, convenient, and fast. Unfortunately, conventional POCT appears stagnant in terms of achieving significant advances. This is attributed to the high cost and instability associated with conventional biorecognition: primarily antibodies, but nucleic acids, cells, enzymes, and aptamers have also been used. Instead, state-of-the-art biosensor researchers are increasingly leveraging molecularly imprinted polymers (MIPs) for their high selectivity, excellent stability, and amenability to a variety of physical and chemical manipulations. Besides the elimination of conventional bioreceptors, the incorporation of nanomaterials has further improved the sensitivity of biosensors. Herein, modern nanobiosensors employing MIPs for selectivity and nanomaterials for improved transduction are systematically reviewed. First, a brief synopsis of fabrication and wide-spread challenges with selectivity demonstration are presented. Afterward, the discussion turns to an analysis of relevant case studies published in the last five years. The analysis is given through two lenses: MIP-based biosensors employing specific nanomaterials and those adopting particular transduction strategies. Finally, conclusions are presented along with a look to the future through recommendations for advancing the field. It is hoped that this work will accelerate successful efforts in the field, orient new researchers, and contribute to equitable health care for all.

Nanomedicine Approaches for Advanced Diagnosis and Treatment of Atherosclerosis and Related Ischemic Diseases

Cardiovascular diseases (CVDs) remain one of the major causes of mortality worldwide. In response to this and other worldwide health epidemics, nanomedicine has emerged as a rapidly evolving discipline that involves the development of innovative nanomaterials and nanotechnologies and their applications in therapy and diagnosis. Nanomedicine presents unique advantages over conventional medicines due to the superior properties intrinsic to nanoscopic therapies. Once used mainly for cancer therapies, recently, tremendous progress has been made in nanomedicine that has led to an overall improvement in the treatment and diagnosis of CVDs. This review elucidates the pathophysiology and potential targets of atherosclerosis and associated ischemic diseases. It may be fruitful to pursue future work in the nanomedicine-mediated treatment of CVDs based on these targets. A comprehensive overview is then provided featuring the latest preclinical and clinical outcomes in cardiovascular imaging, biomarker detection, tissue engineering, and nanoscale delivery, with specific emphasis on nanoparticles, nanostructured scaffolds, and nanosensors. Finally, the challenges and opportunities regarding the future development and clinical translation of nanomedicine in related fields are discussed. Overall, this review aims to provide a deep and thorough understanding of the design, application, and future development of nanomedicine for atherosclerosis and related ischemic diseases.

Bacterial Sensing and Biofilm Monitoring for Infection Diagnostics

Recent insights into the rapidly emerging field of bacterial sensing and biofilm monitoring for infection diagnostics are discussed as well as recent key developments and emerging technologies in the field. Electrochemical sensing of bacteria and bacterial biofilm via synthetic, natural, and engineered recognition, as well as direct redox-sensing approaches via algorithm-based optical sensing, and tailor-made optotracing technology are discussed. These technologies are highlighted to answer the very critical question: "how can fast and accurate bacterial sensing and biofilm monitoring be achieved? Following on from that: "how can these different sensing concepts be translated for use in infection diagnostics? A central obstacle to this transformation is the absence of direct and fast analysis methods that provide high-throughput results and bio-interfaces that can control and regulate the means of communication between biological and electronic systems. Here, the overall progress made to date in building such translational efforts at the level of an individual bacterial cell to a bacterial community is discussed.

Emerging Technologies for the Electrochemical Detection of Bacteria

Infections are a huge economic liability to the health care system, although real-time detection can allow early treatment protocols to avoid some of this cost and patient morbidity and mortality. Pseudomonas aeruginosa (PA) is a drug-resistant gram-negative bacterium found ubiquitously in clinical settings, accounting for up to 27% of hospital acquired infections. PA secretes a vast array of molecules, ranging from secondary metabolites to quorum sensing molecules, of which many can be exploited to monitor bacterial presence. In addition to electrochemical immunoassays to sense bacteria via antigen-antibody interactions, PA pertains a distinct redox-active virulence factor called pyocyanin (PYO), allowing a direct electrochemical detection of the bacteria. There has been a surge of publications relating to the electrochemical tracing of PA via a myriad of novel biosensing techniques, materials, and methodologies. In addition to indirect methods, research approaches where PYO has been sensitively detected using surface modified electrodes are reviewed and compared with conventional PA-sensing methodologies. This review aims at presenting indirect and direct electrochemical methods currently developed using various surface modified electrodes, materials, and electrochemical configurations on their electrocatalytic effects on sensing of PA and in particular PYO.

Mechanical Tolerance of Cascade Bioreactions via Adaptive Curvature Engineering for Epidermal Bioelectronics

Epidermal bioelectronics that can monitor human health status non-invasively and in real time are core to wearable healthcare equipment. Achieving mechanically tolerant surface bioreactions that convert biochemical information to detectable signals is crucial for obtaining high sensing fidelity. In this work, by combining simulations and experiments, a typical epidermal biosensor system is investigated based on a redox enzyme cascade reaction (RECR) comprising glucose oxidase/lactate oxidase enzymes and Prussian blue nanoparticles. Simulations reveal that strain-induced change in surface reactant flux is the key to the performance drop in traditional flat bioelectrodes. In contrast, wavy bioelectrodes capable of curvature adaptation maintain the reactant flux under strain, which preserves sensing fidelity. This rationale is experimentally proven by bioelectrodes with flat/wavy geometry under both static strain and dynamic stretching. When exposed to 50% strain, the signal fluctuations for wavy bioelectrodes are only 7.0% (4.9%) in detecting glucose (lactate), which are significantly lower than the 40.3% (51.8%) in flat bioelectrodes. Based on this wavy bioelectrode, a stable human epidermal metabolite biosensor insensitive to human gestures is further demonstrated. This mechanically tolerant biosensor based on adaptive curvature engineering provides a reliable bio/chemical-information monitoring platform for soft healthcare bioelectronics.

Development of an Ultra-Sensitive and Flexible Piezoresistive Flow Sensor Using Vertical Graphene Nanosheets

This paper suggests development of a flexible, lightweight, and ultra-sensitive piezoresistive flow sensor based on vertical graphene nanosheets (VGNs) with a mazelike structure. The sensor was thoroughly characterized for steady-state and oscillatory water flow monitoring applications. The results demonstrated a high sensitivity (103.91 mV (mm/s)^-1) and a very low-velocity detection threshold (1.127 mm s^-1) in steady-state flow monitoring. As one of many potential applications, we demonstrated that the proposed VGNs/PDMS flow sensor can closely mimic the vestibular hair cell sensors housed inside the semicircular canals (SCCs). As a proof of concept, magnetic resonance imaging of the human inner ear was conducted to measure the dimensions of the SCCs and to develop a 3D printed lateral semicircular canal (LSCC). The sensor was embedded into the artificial LSCC and tested for various physiological movements. The obtained results indicate that the flow sensor is able to distinguish minute changes in the rotational axis physical geometry, frequency, and amplitude. The success of this study paves the way for extending this technology not only to vestibular organ prosthesis but also to other applications such as blood/urine flow monitoring, intravenous therapy (IV), water leakage monitoring, and unmanned underwater robots through incorporation of the appropriate packaging of devices.

A Biosensor for the Detection of Acetylcholine and Diazinon

Acetylcholine is a neurotransmitter and a neuromodulator found in the autonomic, peripheral and central nervous systems. Diazinon is a pesticide with toxic effects on humans, such as the inhibition of acetylcholine. In this paper, a biosensor is proposed for the detection of acetylcholine (range 70 - 1000 μM) and diazinon (range 0.3 - 20000 ppb). This biosensor combines a pH-sensitive layer of reduced graphene oxide functionalized with 4-aminobenzoic acid and acetylcholinesterase. This enzyme was immobilized on reduced graphene oxide and it catalyzed the conversion of acetylcholine into choline and acetic acid, locally decreasing the pH value and triggering the sensor response. The limit of detection for the acetylcholine and diazinon were 70 μM and 0.3 ppb, respectively.

A review on recent developments in optical and electrochemical aptamer-based assays for mycotoxins using advanced nanomaterials

This review (with 163 refs) covers the recent developments of nanomaterial-based optical and electrochemical sensors for mycotoxins. The review starts with a brief discussion on occurrence, distribution, toxicity of mycotoxins and the legislations in monitoring their levels. It further outlines the research methods, various recognition matrices and the strategies involved in the development of highly sensitive and selective sensor systems. It also points out the salient features and importance of aptasensors in the detection of mycotoxins along with the different immobilization methods of aptamers. The review meticulously discusses the performance of different optical and electrochemical sensors fabricated using aptamers coupled with nanomaterials (CNT, graphene, metal nanoparticles and metal oxide nanoparticles). The review addresses the limitations in the current developments as well as the future challenges involved in the successful construction of aptasensors with the functionalized nanomaterials. Graphical abstract Recent developments in nanomaterial based aptasensors for mycotoxins are summarized. Specifically, the efficiency of the nanomaterial coupled aptasensors (such as CNT, graphene, metal nanoparticles and metal oxide nanoparticles) in optical and electrochemical methods are discussed.