A New Electrochemical Multiplexed Assay for PSA Cancer Marker Detection

Duplex Electrochemical Microfluidic Sensor for COVID-19 Antibody Detection: Natural versus Vaccine-Induced Humoral Response

The rapid transmission and resilience of coronavirus disease 2019 (COVID-19) have led to urgent demands in monitoring humoral response for effective vaccine development, thus a multiplex co-detection platform to discriminate infection-induced from vaccine-induced antibodies is needed. Here a duplex electrochemical immunosensor for co-detection of anti-nucleocapsid IgG (N-IgG) and anti-spike IgG (S-IgG) is developed by using a two-working electrode system, via an indirect immunoassay, with antibody quantification obtained by differential pulse voltammetry. The screen-printed electrodes (SPEs) are modified by carbon black and electrodeposited gold nanoflowers for maximized surface areas, enabling the construction of an immunological chain for S-IgG and N-IgG electrochemical detection with enhanced performance. Using an optimized immunoassay protocol, a wide linear range between 30-750 and 20-1000 ng mL-1 , and a limit of detection of 28 and 15 ng mL-1 are achieved to detect N-IgG and S-IgG simultaneously in serum samples. This duplex immunosensor is then integrated in a microfluidic device to obtain significantly reduced detection time (≤ 7 min) while maintaining its analytical performance. The duplex microfluidic immunosensor can be easily expanded into multiplex format to achieve high throughput screening for the sero-surveillance of COVID-19  and other infectious diseases.

Engineering a Point-of-Care Paper-Microfluidic Electrochemical Device Applied to the Multiplexed Quantitative Detection of Biomarkers in Sputum

Health initiatives worldwide demand affordable point-of-care devices to aid in the reduction of morbidity and mortality rates of high-incidence infectious and noncommunicable diseases. However, the production of robust and reliable easy-to-use diagnostic platforms showing the ability to quantitatively measure several biomarkers in physiological fluids and that could in turn be decentralized to reach any relevant environment remains a challenge. Here, we show the particular combination of paper-microfluidic technology, electrochemical transduction, and magnetic nanoparticle-based immunoassay approaches to produce a unique, compact, and easily deployable multiplex device to simultaneously measure interleukin-8, tumor necrosis factor-α, and myeloperoxidase biomarkers in sputum, developed with the aim of facilitating the timely detection of acute exacerbations of chronic obstructive pulmonary disease. The device incorporates an on-chip electrochemical cell array and a multichannel paper component, engineered to be easily aligned into a polymeric cartridge and exchanged if necessary. Calibration curves at clinically relevant biomarker concentration ranges are produced in buffer and artificial sputum. The analysis of sputum samples of healthy individuals and acutely exacerbated patients produces statistically significant biomarker concentration differences between the two studied groups. The device can be mass-produced at a low cost, being an easily adaptable platform for measuring other disease-related target biomarkers.

The critical experimental aspects for developing pathogen electrochemical biosensors: A lesson during the COVID-19 pandemic

Though the bitter global pandemic posed a severe public health threat, it set an unprecedented stage for different research teams to present various technologies for detecting SARS-CoV-2, providing a rare and hard-won lesson for one to comprehensively survey the core experimental aspects in developing pathogens electrochemical biosensors. Apart from collecting all the published biosensor studies, we focused on the effects and consequences of using different receptors, such as antibodies, aptamers, ACE 2, and MIPs, which are one of the core topics of developing a pathogen biosensor. In addition, we tried to find an appropriate and distinctive application scenario (e.g., wastewater-based epidemiology) to maximize the advantages of using electrochemical biosensors to detect pathogens. Based on the enormous amount of information from those published studies, features that fit and favor wastewater pathogen detection can be picked up and integrated into a specific strategy to perform quantitative measurements in wastewater samples.

The Need to Pair Molecular Monitoring Devices with Molecular Imaging to Personalize Health

By enabling the non-invasive monitoring and quantification of biomolecular processes, molecular imaging has dramatically improved our understanding of disease. In recent years, non-invasive access to the molecular drivers of health versus disease has emboldened the goal of precision health, which draws on concepts borrowed from process monitoring in engineering, wherein hundreds of sensors can be employed to develop a model which can be used to preventatively detect and diagnose problems. In translating this monitoring regime from inanimate machines to human beings, precision health posits that continual and on-the-spot monitoring are the next frontiers in molecular medicine. Early biomarker detection and clinical intervention improves individual outcomes and reduces the societal cost of treating chronic and late-stage diseases. However, in current clinical settings, methods of disease diagnoses and monitoring are typically intermittent, based on imprecise risk factors, or self-administered, making optimization of individual patient outcomes an ongoing challenge. Low-cost molecular monitoring devices capable of on-the-spot biomarker analysis at high frequencies, and even continuously, could alter this paradigm of therapy and disease prevention. When these devices are coupled with molecular imaging, they could work together to enable a complete picture of pathogenesis. To meet this need, an active area of research is the development of sensors capable of point-of-care diagnostic monitoring with an emphasis on clinical utility. However, a myriad of challenges must be met, foremost, an integration of the highly specialized molecular tools developed to understand and monitor the molecular causes of disease with clinically accessible techniques. Functioning on the principle of probe-analyte interactions yielding a transducible signal, probes enabling sensing and imaging significantly overlap in design considerations and targeting moieties, however differing in signal interpretation and readout. Integrating molecular sensors with molecular imaging can provide improved data on the personal biomarkers governing disease progression, furthering our understanding of pathogenesis, and providing a positive feedback loop toward identifying additional biomarkers and therapeutics. Coupling molecular imaging with molecular monitoring devices into the clinical paradigm is a key step toward achieving precision health.

On Demand Biosensors for Early Diagnosis of Cancer and Immune Checkpoints Blockade Therapy Monitoring from Liquid Biopsy

Recently, considerable interest has emerged in the development of biosensors to detect biomarkers and immune checkpoints to identify and measure cancer through liquid biopsies. The detection of cancer biomarkers from a small volume of blood is relatively fast compared to the gold standard of tissue biopsies. Traditional immuno-histochemistry (IHC) requires tissue samples obtained using invasive procedures and specific expertise as well as sophisticated instruments. Furthermore, the turnaround for IHC assays is usually several days. To overcome these challenges, on-demand biosensor-based assays were developed to provide more immediate prognostic information for clinicians. Novel rapid, highly precise, and sensitive approaches have been under investigation using physical and biochemical methods to sense biomarkers. Additionally, interest in understanding immune checkpoints has facilitated the rapid detection of cancer prognosis from liquid biopsies. Typically, these devices combine various classes of detectors with digital outputs for the measurement of soluble cancer or immune checkpoint (IC) markers from liquid biopsy samples. These sensor devices have two key advantages: (a) a small volume of blood drawn from the patient is sufficient for analysis, and (b) it could aid physicians in quickly selecting and deciding the appropriate therapy regime for the patients (e.g., immune checkpoint blockade (ICB) therapy). In this review, we will provide updates on potential cancer markers, various biosensors in cancer diagnosis, and the corresponding limits of detection, while focusing on biosensor development for IC marker detection.

Prospects and challenges of using electrochemical immunosensors as an alternative detection method for SARS-CoV-2 wastewater-based epidemiology

Given its potential applications in confronting the COVID-19 pandemic, wastewater-based epidemiology (WBE) has attracted tremendous attention. Developing a fast, cost-effective, and practical method for SARS-CoV-2 detection in wastewater is of great significance to facilitate future WBE development. By now, the PCR-based approach serves as the reference method and “gold standard” to detect the virus in wastewater. However, we found a trend that the PCR-based method becomes almost an unshakable choice as more and more studies were published regarding SARS-CoV-2 WBE. Of note, the importance of exploring new, alternative approaches for SARS-CoV-2 detection in wastewater should not be underestimated. In this context, the prospect of using electrochemical immunosensors as the alternative detection method was investigated in this survey. Based on the previous efforts towards different virus immunoassay studies and newly published PCR-based COVD-19 WBE works, this survey provides new insights into the electrochemical immunoassay that have been widely adopted in body fluids virus detection, along with an extensive discussion of the detection mechanism, detection performance, past performances, current efforts, and potential challenges with wastewater detection. In the end, this survey concludes that using electrochemical immunosensors to analyze SARS-CoV-2 in wastewater samples quantitatively may have better feasibility and practicability than using the conventional PCR-based approach, especially when considering its fast detection, ease of miniaturization, and potential on-site measurement.

Electrochemical prostate-specific antigen biosensors based on electroconductive nanomaterials and polymers

Prostate cancer (PCa), the second most malignant neoplasm in men, is also the fifth leading cause of cancer-related deaths in men globally. Unfortunately, this malignancy remains largely asymptomatic until late-stage emergence when treatment is limited due to the lack of effective metastatic PCa therapeutics. Due to these limitations, early PCa detection through prostate-specific antigen (PSA) screening has become increasingly important, resulting in a more than 50% decrease in mortality. Conventional assays for PSA detection, such as enzyme-linked immunosorbent assay (ELISA), are labor intensive, relatively expensive, operator-dependent and do not provide adequate sensitivity. Electrochemical biosensors overcome these limitations because they are rapid, cost-effective, simple to use and ultrasensitive. This article reviews electrochemical PSA biosensors using electroconductive nanomaterials such as carbon-, metal-, metal oxide- and peptide-based nanostructures, as well as polymers to significantly improve conductivity and enhance sensitivity. Challenges associated with the development of these devices are discussed thus providing additional insight into their analytic strength as well as their potential use in early PCa detection.

Suppressing Non-Specific Binding of Proteins onto Electrode Surfaces in the Development of Electrochemical Immunosensors

Electrochemical immunosensors, EIs, are systems that combine the analytical power of electrochemical techniques and the high selectivity and specificity of antibodies in a solid phase immunoassay for target analyte. In EIs, the most used transducer platforms are screen printed electrodes, SPEs. Some characteristics of EIs are their low cost, portability for point of care testing (POCT) applications, high specificity and selectivity to the target molecule, low sample and reagent consumption and easy to use. Despite all these attractive features, still exist one to cover and it is the enhancement of the sensitivity of the EIs. In this review, an approach to understand how this can be achieved is presented. First, it is necessary to comprise thoroughly all the complex phenomena that happen simultaneously in the protein-surface interface when adsorption of the protein occurs. Physicochemical properties of the protein and the surface as well as the adsorption phenomena influence the sensitivity of the EIs. From this point, some strategies to suppress non-specific binding, NSB, of proteins onto electrode surfaces in order to improve the sensitivity of EIs are mentioned.

Use of data processing for rapid detection of the prostate-specific antigen biomarker using immunomagnetic sandwich-type sensors

Diagnosis of cancer using electroanalytical methods can be achieved at low cost and in rapid assays, but this may require the combination with data treatment for determining biomarkers in real samples. In this paper, we report an immunomagnetic nanoparticle-based microfluidic sensor (INμ-SPCE) for the amperometric detection of the prostate-specific antigen (PSA) biomarker, the data of which were treated with information visualization methods. The INμ-SPCE consists of eight working electrodes, reference and counter electrodes. On the working electrodes, magnetic nanoparticles with secondary antibodies with the enzyme horseradish peroxidase were immobilized for the indirect detection of PSA in a sandwich-type procedure. Under optimal conditions, the immunosensor could operate within a wide range from 12.5 to 1111 fg·L^-1, with a low detection limit of 0.062 fg·L^-1. Multidimensional projections combined with feature selection allowed for the distinction of cell lysates with different levels of PSA, in agreement with results from the traditional enzyme-linked immunosorbent assay. The approaches for immunoassays and data processing are generic, and therefore the strategies described here may provide a simple platform for clinical diagnosis of cancers and other types of diseases.

MICROFLUIDIC CHIP FOR CANCER CELL DETECTION AND DIAGNOSIS

Since cancer becomes the most deadly disease to our health, research on early detection on cancer cells is necessary for clinical treatment. The combination of microfluidic device with cell biology has shown a unique method for cancer cell research. In the present review, recent development on microfluidic chip for cancer cell detection and diagnosis will be addressed. Some typical microfluidic chips focussed on cancer cells and their advantages for different kinds of cancer cell detection and diagnosis will be listed, and the cell capture methods within the microfluidics will be simultaneously mentioned. Then the potential direction of microfluidic chip on cancer cell detection and diagnosis in the future is also discussed.

Critical overview on the application of sensors and biosensors for clinical analysis

Sensors and biosensors have been increasingly used for clinical analysis due to their miniaturization and portability, allowing the construction of diagnostic devices for point-of-care testing. This paper presents an up-to-date overview and comparison of the analytical performance of sensors and biosensors recently used in clinical analysis. This includes cancer and cardiac biomarkers, hormones, biomolecules, neurotransmitters, bacteria, virus and cancer cells, along with related significant advances since 2011. Some methods of enhancing the analytical performance of sensors and biosensors through their figures of merit are also discussed.

Acetamiprid multidetection by disposable electrochemical DNA aptasensor

In this work, we propose an electrochemical DNA aptasensor for sensitive multidetection of acetamiprid based on a competitive format and disposable screen-printed arrays. To improve the sensitivity of the aptasensor, polyaniline film and gold nanoparticles were progressively electrodeposited on the graphite screen-printed electrode surface by cyclic voltammetry. Gold nanoparticles were then employed as platform for thiol-tethered DNA aptamer immobilization. Different acetamiprid solutions containing a fixed amount of biotinylated complementary oligonucleotide sequence by DNA aptasensor arrays were analyzed. Streptavidin-alkaline phosphatase conjugate was then added to trace the affinity reaction. The enzyme catalyzed the hydrolysis of 1-naphthyl phosphate to 1-naphthol. The enzymatic product was detected by differential pulse voltammetry. A decrease of the signal was obtained when the pesticide concentration was increased, making the sensor work as signal off sensor. Under optimized conditions by testing key experimental parameters, a dose-response curve was constructed between 0.25 and 2.0µM acetamiprid concentration range and a limit of detection of 0.086µM was calculated. The selectivity of the aptasensor was also confirmed by the analysis of atrazine pesticide. Finally, preliminary experiments in fruit juice samples spiked with acetamiprid were also performed.

Electrochemical, Electrochemiluminescence, and Photoelectrochemical Aptamer-Based Nanostructured Sensors for Biomarker Analysis

Aptamer-based sensors have been intensively investigated as potential analytical tools in clinical analysis providing the desired portability, fast response, sensitivity, and specificity, in addition to lower cost and simplicity versus conventional methods. The aim of this review, without pretending to be exhaustive, is to give the readers an overview of recent important achievements about electrochemical, electrochemiluminescence, and photoelectrochemical aptasensors for the protein biomarker determination, mainly cancer related biomarkers, by selected recent publications. Special emphasis is placed on nanostructured-based aptasensors, which show a substantial improvement of the analytical performances.

Biomedical Perspective of Electrochemical Nanobiosensor

Electrochemical biosensor holds great promise in the biomedical area due to its enhanced specificity, sensitivity, label-free nature and cost effectiveness for rapid point-of-care detection of diseases at bedside. In this review, we are focusing on the working principle of electrochemical biosensor and how it can be employed in detecting biomarkers of fatal diseases like cancer, AIDS, hepatitis and cardiovascular diseases. Recent advances in the development of implantable biosensors and exploration of nanomaterials in fabrication of electrodes with increasing the sensitivity of biosensor for quick and easy detection of biomolecules have been elucidated in detail. Electrochemical-based detection of heavy metal ions which cause harmful effect on human health has been discussed. Key challenges associated with the electrochemical sensor and its future perspectives are also addressed.

Immunosensors in Clinical Laboratory Diagnostics

The application of simple, cost-effective, rapid, and accurate diagnostic technologies for detection and identification of cardiac and cancer biomarkers has been a central point in the clinical area. Biosensors have been recognized as efficient alternatives for the diagnostics of various diseases due to their specificity and potential for application on real samples. The role of nanotechnology in the construction of immunological biosensors, that is, immunosensors, has contributed to the improvement of sensitivity, since they are based in the affinity between antibody and antigen. Other analytes than biomarkers such as hormones, pathogenic bacteria, and virus have also been detected by immunosensors for clinical point-of-care applications. In this chapter, we first introduced the various types of immunosensors and discussed their applications in clinical diagnostics over the recent 6 years, mainly as point-of-care technologies for the determination of cardiac and cancer biomarkers, hormones, pathogenic bacteria, and virus. The future perspectives of these devices in the field of clinical diagnostics are also evaluated.

Affinity biosensors for tumor-marker analysis

The use of cancer biomarkers is emerging as one of the most promising strategies for early detection and management of cancer. Biosensors can provide advanced platforms for biomarker analysis with the advantages of being easy to use, inexpensive, rapid and offering multi-analyte testing capability. The intention of this article is to discuss recent advances and trends in affinity biosensors for cancer diagnosis, prognosis and even theragnosis. The different types of affinity biosensors will be reviewed in terms of molecular recognition element. Current challenges and trends for this technology will be also discussed, with a particular emphasis on recent developments in miRNA detection.

Proximity hybridization regulated DNA biogate for sensitive electrochemical immunoassay

An electrochemical DNA biogate was designed for highly sensitive homogeneous electrochemical immunoassay by combining target-induced proximity hybridization with a mesoporous silica nanoprobe (MSN). The electroactive methylene blue (MB) was sealed in the inner pores of MSN with single-stranded DNA. In the presence of target protein and two DNA-labeled antibodies, the formed proximate complex could hybridize with the DNA strand to form a rigid double-stranded structure and thus open the biogate, which led to the release of MB entrapped in the MSN. The target protein-dependent amount of released MB could be conveniently monitored with a screen-printed carbon electrode. Moreover, the detachment process of MB could be further amplified with an in situ enzymatic recycling binding of the proximate complex with the single-stranded DNA. Using prostate-specific antigen as a model target, the proposed assay showed a wide detection range from 0.002 to 100 ng mL(-1) with a detection limit of 1.3 pg mL(-1). This strategy was simple and universal for various analytes with different affinity ligands. This method possessed great potential for convenient point-of-care testing and commercial application.

Ratiometric electrochemical proximity assay for sensitive one-step protein detection

This work proposes the concept of ratiometric electrochemical proximity assay (REPA), which can be used for one-step, highly sensitive and selective detection of protein. The assay strategy was achieved on a sensing interface that was formed by hybridization of methylene blue (MB)-labeled antibody-DNA probe (MB-DNA1-Ab1) with ferrocene (Fc)-labeled DNA capture probe (Fc-P) modified gold electrode. On the interface the target protein could trigger the formation of immunocomplex between MB-DNA1-Ab1 and detection antibody-DNA probe (Ab2-DNA2) and subsequently the proximity hybridization of DNA1-DNA2, which led to the departure of MB-DNA1-Ab1 from the interface. The remained Fc-P could form a hairpin structure to take Fc group to electrode surface. Therefore, the recognition of target protein to Ab1 and Ab2 resulted in both the "signal-off" of MB and the "signal-on" of Fc for dual-signal electrochemical ratiometric readout. The proposed REPA could be carried out in one-step with 40-min duration and showed a wide detection range from 0.05 to 100 ng/mL with pg/mL limit of detection, displaying great potential for convenient point-of-care testing and commercial application.

Ultrasensitive protein detection: a case for microfluidic magnetic bead-based assays

We review the use of magnetic micro- and nanoparticles ('magnetic beads') in microfluidic systems for ultrasensitive protein detection. During recent years magnetic beads have been used frequently in immunoassays, either as mobile substrates on which the target antigen is captured, as detection labels, or simultaneously as substrates and labels. The major part of the reviewed work has as application the detection of antibodies or disease biomarkers in serum or of biotoxins from food samples. Several of the most sensitive assays allow protein detection down to fg mL(-1) concentrations. We benchmark the performance of these microfluidic magnetic bead-based assays with the most promising earlier work and with alternative solutions.

On-chip screening for prostate cancer: an EIS microfluidic platform for contemporary detection of free and total PSA

Prostate cancer affects a large part of the western male population. The need for an early and accurate detection is thus a great challenge in common clinical practice, but the lack of specificity of the serum marker PSA (Prostate Specific Antigen) is a serious problem since its increased concentration can be related to several abnormalities. PSA, however, is found in serum in both a free and a complexed form with other proteins and the percentage amount of unbound PSA (the free-to-total PSA ratio) can be employed to distinguish prostate cancer from benign prostatic conditions, and also to predict the future risk of prostate cancer. To improve the operating characteristics of current PSA tests and to provide a clinical tool able to run label-free and sensitive analysis, we thus developed a biosensing platform based on Electrochemical Impedance Spectroscopy (EIS), which allows the contemporary detection of free and total PSA on a single biochip, enabling a quick screening for the risk of prostate cancer thanks to the presence of two different immobilized antibodies specific for the different antigens researched.

Applications of microfluidics for molecular diagnostics

Diagnostic assays implemented in microfluidic devices have developed rapidly over the past decade and are expected to become commonplace in the next few years. Hundreds of microfluidics-based approaches towards clinical diagnostics and pathogen detection have been reported with a general theme of rapid and customizable assays that are potentially cost-effective. This chapter reviews microfluidics in molecular diagnostics based on application areas with a concise review of microfluidics in general. Basic principles of microfabrication are briefly reviewed and the transition to polymer fabricated devices is discussed. Most current microfluidic diagnostic devices are designed to target a single disease, such as a given cancer or a variety of pathogens, and there will likely be a large market for these focused devices; however, the future of molecular diagnostics lies in highly multiplexed microfluidic devices that can screen for potentially hundreds of diseases simultaneously.

Electrochemical immunosensors for detection of cancer protein biomarkers

Bioanalytical methods have experienced unprecedented growth in recent years, driven in large part by the need for faster, more sensitive, more portable ("point of care") systems to detect protein biomarkers for clinical diagnosis. Electrochemical detection strategies, used in conjunction with immunosensors, offer advantages because they are fast, simple, and low cost. Recent developments in electrochemical immunosensors have significantly improved the sensitivity needed to detect low concentrations of biomarkers present in early stages of cancer. Moreover, the coupling of electrochemical devices with nanomaterials, such as gold nanoparticles, carbon nanotubes, magnetic particles, and quantum dots, offers multiplexing capability for simultaneous measurements of multiple cancer biomarkers. This review will discuss recent advances in the development of electrochemical immunosensors for the next generation of cancer diagnostics, with an emphasis on opportunities for further improvement in cancer diagnostics and treatment monitoring. Details will be given for strategies to increase sensitivity through multilabel amplification, coupled with high densities of capture molecules on sensor surfaces. Such sensors are capable of detecting a wide range of protein quantities, from nanogram to femtogram (depending on the protein biomarkers of interest), in a single sample.

Magnetic particles in ultrasensitive biomarker protein measurements for cancer detection and monitoring

IMPORTANCE OF THE FIELD: Devices for the reliable detection of panels of biomarker proteins facilitated by magnetic bead-based technologies have the potential to greatly improve future cancer diagnostics. The reason for this review is to highlight promising research on emerging procedures for protein capture, transport and detection featuring magnetic particles. AREAS COVERED IN THIS REVIEW: The review covers applications of magnetic particles in protein immunoassays in emerging research and commercial methods, and stresses multiplexed protein assays for reliable future cancer diagnostics. Research literature over the past dozen years has been surveyed and specific examples are presented in detail. EXPERT OPINION: Magnetic particles are important components of emerging protein detection systems. They need to be integrated into simple inexpensive systems for accurate, sensitive detection of fully validated panels of biomarker proteins to be widely useful in clinical cancer diagnostics.