Rapid and label-free electrochemical DNA biosensor based on a facile one-step electrochemical synthesis of rGO-PPy-(L-Cys)-AuNPs nanocomposite for the HTLV-1 oligonucleotide detection

Electrochemical biosensors in early leukemia detection

Leukemia, a type of blood cancer marked by an abnormal increase in white blood cells, poses a significant challenge to healthcare. The key to successful treatment lies in early detection. However, traditional methods often fall short. This review investigates the potential of electrochemical biosensors for a more accurate and earlier diagnosis of leukemia. Electrochemical biosensors are compact devices that transform biological interactions into electrical signals. Their small size, ease of use, and minimal sample requirements make them perfectly suited for point-of-care applications. Their remarkable sensitivity and specificity enable the detection of subtle biomolecular changes associated with leukemia, which is crucial for early disease detection. This review delves into studies that have utilized these biosensors to identify various types of leukemia. It examines the roles of electrodes, biorecognition elements, and signal transduction mechanisms. The discussion includes the integration of nanomaterials such as gold nanoparticles and nitrogen-doped graphene into biosensor design. These materials boost sensitivity, enhance signal amplification, and facilitate multi-analyte detection, thereby providing a more holistic view of the disease. Beyond technical advancements, the review underscores the practical benefits of these biosensors. Their portability makes them a promising tool for resource-constrained settings, enabling swift diagnosis in remote areas or at a patient's bedside. The potential for monitoring treatment effectiveness and detecting minimal residual disease to prevent relapse is also explored. This review emphasizes the transformative potential of electrochemical biosensors in combating leukemia. By facilitating earlier and more accurate diagnosis, these biosensors stand to revolutionize patient care and enhance treatment outcomes.

A portable label-free electrochemical DNA biosensor for rapid detection of Salmonella Typhi

A highly accurate, rapid, portable, and robust platform for detecting Salmonella enterica serovar Typhi (S. Typhi) is crucial for early-stage diagnosis of typhoid to avert and control the outbreaks of this pathogen, which threaten global public health. This study presents a proof-of-concept for our developed label-free electrochemical DNA biosensor system for S. Typhi detection, which employs a printed circuit board gold electrode (PCBGE), integrated with a portable potentiostat reader. Initially, the functionalized DNA biosensor and target detection were characterized using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods using a benchtop potentiostat. Interestingly, the newly developed DNA biosensor can identify target single-stranded DNA concentrations ranging from 10 nM to 20 μM, achieving a detection limit of 7.6 nM within a brief 5 minute timeframe. Under optimal detection conditions, the DNA biosensor exhibits remarkable selectivity, capable of distinguishing a single mismatch base pair from the target single-stranded DNA sequence. We then evaluated the feasibility of the developed DNA biosensor system as a diagnostic tool by detecting S. Typhi in 50 clinical samples using a portable potentiostat reader based on the DPV technique. Remarkably, the developed biosensor can distinctly distinguish between positive and negative samples, indicating that the miniaturised DNA biosensor system is practical for detecting S. Typhi in real biological samples. The developed DNA biosensor device in this work proves to be a promising point-of-care (POC) device for Salmonella detection due to its swift detection time, uncomplicated design, and streamlined workflow detection system.

Development of optical and electrochemical immunodevices for dengue virus detection

Dengue virus (DENV) is the most prevalent global arbovirus, exhibiting a high worldwide incidence with intensified severity of symptoms and alarming mortality rates. Faced with the limitations of diagnostic methods, an optical and electrochemical biosystem was developed for the detection of DENV genotypes 1 and 2, using cysteine (Cys), cadmium telluride (CdTe) quantum dots, and anti-DENV antibodies. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), surface plasmon resonance (SPR), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the immunosensor. The AFM and SPR results demonstrated discernible topographic and angular changes confirming the biomolecular recognition. Different concentrations of DENV-1 and DENV-2 were evaluated (0.05 × 106 to 2.0 × 106 PFU mL-1), resulting in a maximum anodic shift (ΔI%) of 263.67% ± 12.54 for DENV-1 and 63.36% ± 3.68 for DENV-2. The detection strategies exhibited a linear response to the increase in viral concentration. Excellent linear correlations, with R2 values of 0.95391 for DENV-1 and 0.97773 for DENV-2, were obtained across a broad concentration range. Data analysis demonstrated high reproducibility, displaying relative standard deviation values of 3.42% and 3.62% for Cys-CdTe-antibodyDENV-1-BSA and Cys-CdTe-antibodyDENV-2-BSA systems. The detection limits were 0.34 × 106 PFU mL-1 and 0.02 × 106 PFU mL-1, while the quantification limits were set at 1.49 × 106 PFU mL-1 and 0.06 × 106 PFU mL-1 for DENV-1 and DENV-2, respectively. Therefore, the biosensing apparatus demonstrates analytical effectiveness in viral screening and can be considered an innovative solution for early dengue diagnosis, contributing to global public health.

Electrochemical Sensors and Biosensors for Identification of Viruses: A Critical Review

Due to their life cycle, viruses can disrupt the metabolism of their hosts, causing diseases. If we want to disrupt their life cycle, it is necessary to identify their presence. For this purpose, it is possible to use several molecular-biological and bioanalytical methods. The reference selection was performed based on electronic databases (2020-2023). This review focused on electrochemical methods with high sensitivity and selectivity (53% voltammetry/amperometry, 33% impedance, and 12% other methods) which showed their great potential for detecting various viruses. Moreover, the aforementioned electrochemical methods have considerable potential to be applicable for care-point use as they are portable due to their miniaturizability and fast speed analysis (minutes to hours), and are relatively easy to interpret. A total of 2011 articles were found, of which 86 original papers were subsequently evaluated (the majority of which are focused on human pathogens, whereas articles dealing with plant pathogens are in the minority). Thirty-two species of viruses were included in the evaluation. It was found that most of the examined research studies (77%) used nanotechnological modifications. Other ones performed immunological (52%) or genetic analyses (43%) for virus detection. 5% of the reports used peptides to increase the method's sensitivity. When evaluable, 65% of the research studies had LOD values in the order of ng or nM. The vast majority (79%) of the studies represent proof of concept and possibilities with low application potential and a high need of further research experimental work.

Designing a label-free electrochemical aptasensor based on polypyrrole-l-cysteine-reduced graphene oxide nanocomposite for detection of 25-hydroxyvitamin D3

Reliable and precise quantification of 25-hydroxyvitamin D3 in clinical samples is vital because vitamin D3 deficiency lead to several disorders, such as mental illness, osteoporosis, and coronavirus disease. Herein, we report the fabrication of a novel electrochemical aptasensor using a nanocomposite, including reduced graphene oxide, pyrrole, and l-cysteine, for the sensitive detection of 25-hydroxyvitamin D3 . Subsequently, the aptamer of 25-hydroxyvitamin D3 was immobilized on the surface of the modified electrode. Differential pulse voltammetry signals were utilized for studying the binding and measurement of 25-hydroxyvitamin D3 based on the oxidation peak. Under the optimum conditions, the designed electrochemical aptasensor exhibited a linear detection range of 0.001-150 nM, with a limit of detection of 0.006 nM. Furthermore, the proposed aptasensor selectively detected 25-hydroxyvitamin D3 compared to other analogs. Moreover, this aptasensor was successfully applied for the detection of 25-hydroxyvitamin D3 in human serum samples, which were quantified by the enzyme-linked immunosorbent assay method. The acceptable recoveries of 82.67%-111.07% demonstrated that this proposed electrochemical aptasensor can be a promising alternative for clinical methods of vitamin D determination.

Label-Free DNA Biosensor Based on Reduced Graphene Oxide and Gold Nanoparticles

Currently available DNA detection techniques frequently require compromises between simplicity, speed, accuracy, and cost. Here, we propose a simple, label-free, and cost-effective DNA detection platform developed at screen-printed carbon electrodes (SPCEs) modified with reduced graphene oxide (RGO) and gold nanoparticles (AuNPs). The preparation of the detection platform involved a two-step electrochemical procedure based on GO reduction onto SPCEs followed by the electrochemical reduction of HAuCl4 to facilitate the post-grafting reaction with AuNPs. The final sensor was fabricated by the simple physical adsorption of a single-stranded DNA (ssDNA) probe onto a AuNPs-RGO/SPCE electrode. Each preparation step was confirmed by morphological and structural characterization using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy, respectively. Furthermore, the electrochemical properties of the modified electrodes have been investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results demonstrated that the introduction of AuNPs onto RGO/SPCEs led to an enhancement in surface conductivity, a characteristic that favored an increased sensitivity in detection. The detection process relied on the change in the electrochemical signal induced by the binding of target DNA to the bioreceptor and was particularly monitored by the change in the charge transfer resistance of a [Fe(CN)6]4-/3- redox couple added in the test solution.

Carbon Nanomaterials-Based Screen-Printed Electrodes for Sensing Applications

Electrochemical sensors consisting of screen-printed electrodes (SPEs) are recurrent devices in the recent literature for applications in different fields of interest and contribute to the expanding electroanalytical chemistry field. This is due to inherent characteristics that can be better (or only) achieved with the use of SPEs, including miniaturization, cost reduction, lower sample consumption, compatibility with portable equipment, and disposability. SPEs are also quite versatile; they can be manufactured using different formulations of conductive inks and substrates, and are of varied designs. Naturally, the analytical performance of SPEs is directly affected by the quality of the material used for printing and modifying the electrodes. In this sense, the most varied carbon nanomaterials have been explored for the preparation and modification of SPEs, providing devices with an enhanced electrochemical response and greater sensitivity, in addition to functionalized surfaces that can immobilize biological agents for the manufacture of biosensors. Considering the relevance and timeliness of the topic, this review aimed to provide an overview of the current scenario of the use of carbonaceous nanomaterials in the context of making electrochemical SPE sensors, from which different approaches will be presented, exploring materials traditionally investigated in electrochemistry, such as graphene, carbon nanotubes, carbon black, and those more recently investigated for this (carbon quantum dots, graphitic carbon nitride, and biochar). Perspectives on the use and expansion of these devices are also considered.

A novel electrochemical biosensor based on signal amplification of Au HFGNs/PnBA-MXene nanocomposite for the detection of miRNA-122 as a biomarker of breast cancer

Cancer is one of the leading causes of death worldwide and a crisis for global health. Breast cancer is the second most common cancer globally. In the perusal, a novel electrochemical biosensor amplified with hierarchical flower-like gold, poly (n-butyl acrylate), and MXene (AuHFGNs/PnBA-MXene) nanocomposite and activated by highly special antisense ssDNA (single-stranded DNA) provide a promising alternative for miRNA-122 detection as a biomarker of breast cancer. The biosensor presented a detection limit of 0.0035 aM (S/N = 3) with a linear range from 0.01 aM to 10 nM. The platform was tried on 20 breast cancer miRNAs extracted from actual serum specimens (10 positives and 10 negatives). Founded on the quantitatively obtained outcomes and statistic analysis (t-test, box-graph, receiver performance characteristic curve, and cut-off amount), the biosensor showed a meaningful discrepancy between the native and positive groups with 100% specificity and 100% sensitivity. While, RT-qPCR showed less specificity and sensitivity (70% specificity, 100% sensitivity) than the proposed biosensor. To assess the quantitative capacity and biosensor detection limit for clinical tests, the biosensor diagnosis performance for continually diluted miRNA extracted from patients was compared to that gained by RT-qPCR results, indicating that the biosensor detection limit was lower than RT-qPCR. ssDNA/AuHFGN/PnBA-MXene/GCE displayed little cross-reaction with other sequences and also showed desirable stability, reproducibility, and specificity and stayed stable until 32 days. As a result, the designed biosensor can perform as a hopeful method for diagnosis applications.

A label-free electrochemical DNA biosensor used a printed circuit board gold electrode (PCBGE) to detect SARS-CoV-2 without amplification

The emergence of coronavirus disease 2019 (COVID-19) motivates continuous efforts to develop robust and accurate diagnostic tests to detect severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Detection of viral nucleic acids provides the highest sensitivity and selectivity for diagnosing early and asymptomatic infection because the human immune system may not be active at this stage. Therefore, this work aims to develop a label-free electrochemical DNA biosensor for SARS-CoV-2 detection using a printed circuit board-based gold substrate (PCBGE). The developed sensor used the nucleocapsid phosphoprotein (N) gene as a biomarker. The DNA sensor-based PCBGE was fabricated by self-assembling a thiolated single-stranded DNA (ssDNA) probe onto an Au surface, which performed as the working electrode (WE). The Au surface was then treated with 6-mercapto-1-hexanol (MCH) before detecting the target N gene to produce a well-oriented arrangement of the immobilized ssDNA chains. The successful fabrication of the biosensor was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM). The DNA biosensor performances were evaluated using a synthetic SARS-CoV-2 genome and 20 clinical RNA samples from healthy and infected individuals through EIS. The developed DNA biosensor can detect as low as 1 copy per μL of the N gene within 5 minutes with a LOD of 0.50 μM. Interestingly, the proposed DNA sensor could distinguish the expression of SARS-CoV-2 RNA in a patient diagnosed with COVID-19 without any amplification technique. We believe that the proposed DNA sensor platform is a promising point-of-care (POC) device for COVID-19 viral infection since it offers a rapid detection time with a simple design and workflow detection system, as well as an affordable diagnostic assay.

Application of Polypyrrole-Based Electrochemical Biosensor for the Early Diagnosis of Colorectal Cancer

Although colorectal cancer (CRC) is easy to treat surgically and can be combined with postoperative chemotherapy, its five-year survival rate is still not optimistic. Therefore, developing sensitive, efficient, and compliant detection technology is essential to diagnose CRC at an early stage, providing more opportunities for effective treatment and intervention. Currently, the widely used clinical CRC detection methods include endoscopy, stool examination, imaging modalities, and tumor biomarker detection; among them, blood biomarkers, a noninvasive strategy for CRC screening, have shown significant potential for early diagnosis, prediction, prognosis, and staging of cancer. As shown by recent studies, electrochemical biosensors have attracted extensive attention for the detection of blood biomarkers because of their advantages of being cost-effective and having sound sensitivity, good versatility, high selectivity, and a fast response. Among these, nano-conductive polymer materials, especially the conductive polymer polypyrrole (PPy), have been broadly applied to improve sensing performance due to their excellent electrical properties and the flexibility of their surface properties, as well as their easy preparation and functionalization and good biocompatibility. This review mainly discusses the characteristics of PPy-based biosensors, their synthetic methods, and their application for the detection of CRC biomarkers. Finally, the opportunities and challenges related to the use of PPy-based sensors for diagnosing CRC are also discussed.

Fabrication of a Free-Standing MWCNT Electrode by Electric Field Force for an Ultra-Sensitive MicroRNA-21 Nano-Genosensor

Abnormal expression of microRNA-21 (miR-21) is considered to be closely associated with the pathogenesis of colorectal cancer. However, great challenges do exist for the development of ultra-sensitive biosensors to detect the abnormal expression of miR-21 due to the low concentration in serum (fm level) at the early stage of colorectal cancer. Therefore, electric field force is used to rotate and rearrange random multi-walled carbon nanotubes (MWCNTs) at the microscale to improve the active sites of the electrode in this study. The free-standing MWCNTs are densely and high-orderly embedded into the bare electrode along the direction of the electric field. Compared to the bare electrode, the peak-current response of the free-standing MWCNT electrode improves by 150 times in cyclic voltammetric measurement. A nano-genosensor based on the free-standing MWCNT electrode is developed for measuring miR-21. The nano-genosensor for miR-21 shows an ultra-high sensitivity of 48.24 µA µm^-1 , a wide linear range from 0.01 × 10^-15 to 100 × 10^-12 m, and a low detection limit of 1.2 × 10^-18 m. The present nano-genosensor shows superior performance for miR-21 in human serum samples and demonstrates a potential application for the diagnosis of early stage colorectal cancer.

Highly Sensitive Electrochemical Immunosensor Platforms for Dual Detection of SARS-CoV-2 Antigen and Antibody based on Gold Nanoparticle Functionalized Graphene Oxide Nanocomposites

In this work, we report a facile synthesis of graphene oxide-gold (GO-Au) nanocomposites by electrodeposition. The fabricated electrochemical immunosensors are utilized for the dual detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen and SARS-CoV-2 antibody. The GO-Au nanocomposites has been characterized by UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) for its biosensing properties. The linear detection range of the SARS-CoV-2 antigen immunosensor is 10.0 ag mL-1 to 50.0 ng mL-1, whereas that for the antibody immunosensor ranges from 1.0 fg mL-1 to 1.0 ng mL-1. The calculated limit of detection (LOD) of the SARS-CoV-2 antigen immunosensor is 3.99 ag mL-1, and that for SARS-CoV-2 antibody immunosensor is 1.0 fg mL-1 with high sensitivity. The validation of the immunosensor has also been carried out on patient serum and patient swab samples from COVID-19 patients. The results suggest successful utilization of the immunosensors with a very low detection limit enabling its use in clinical samples. Further work is needed for the standardization of the results and translation in screen-printed electrodes for use in portable commercial applications.

Nanostructured sensor platform based on organic polymer conjugated to metallic nanoparticle for the impedimetric detection of SARS-CoV-2 at various stages of viral infection

The projection of new biosensing technologies for genetic identification of SARS-COV-2 is essential in the face of a pandemic scenario. For this reason, the current research aims to develop a label-free flexible biodevice applicable to COVID-19. A nanostructured platform made of polypyrrole (PPy) and gold nanoparticles (GNP) was designed for interfacing the electrochemical signal in miniaturized electrodes of tin-doped indium oxide (ITO). Oligonucleotide primer was chemically immobilized on the flexible transducers for the biorecognition of the nucleocapsid protein (N) gene. Methodological protocols based on cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM) were used to characterize the nanotechnological apparatus. The biosensor’s electrochemical performance was evaluated using the SARS-CoV-2 genome and biological samples of cDNA from patients infected with retrovirus at various disease stages. It is inferred that the analytical tool was able to distinguish the expression of SARS-CoV-2 in patients diagnosed with COVID-19 in the early, intermediate and late stages. The biosensor exhibited high selectivity by not recognizing the biological target in samples from patients not infected with SARS-CoV-2. The proposed sensor obtained a linear response range estimated from 800 to 4000 copies µL⁻¹ with a regression coefficient of 0.99, and a detection limit of 258.01 copies µL⁻¹. Therefore, the electrochemical biosensor based on flexible electrode technology represents a promising trend for sensitive molecular analysis of etiologic agent with fast and simple operationalization. In addition to early genetic diagnosis, the biomolecular assay may help to monitor the progression of COVID-19 infection in a novel manner.

Comparison between various biosensor methods for human T-lymphotropic virus-1 (HTLV-1) detection

Due to the drawback of traditional and current diagnostic methods including serological and molecular assays, the development of the rapid and free-PCR techniques can be an alternative technique for the human T-cell lymphotropic virus (HTLV-1) DNA detection sequences. On the other hand, early detection of HTLV-1 prevents two dangerous diseases including Adult T-cell leukemia/lymphoma and HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis. The biosensor-based methods are sensitive techniques that can provide new opportunities to detect infectious diseases, particularly in the early stage. This study provides a comparative view among recently designed biosensors for the detection of HTLV-1.

Response surface methodology optimized electrochemical DNA biosensor based on HAPNPTs/PPY/MWCNTs nanocomposite for detecting Mycobacterium tuberculosis

An important issue in the prognosis of tuberculosis (TB) is a short period between correct diagnosis and start the suitable antibiotic therapy. So, a rapid and valid method for detection of Mycobacterium tuberculosis (M. tb) complex is considered as a necessity. Herein, a rapid, low-cost, and PCR-free DNA biosensor was developed based on multi-walled carbon nanotubes (MWCNTs), polypyrrole (PPy), and hydroxyapatite nanoparticles (HAPNPs) for highly sensitive and specific recognition of M.tb. The biosensor consisted of M.tb ssDNA probe covalently attached to the HANPs/PPy/MWCNTs/GCE surface that hybridized to a complementary target sequence to form a duplex DNA. The M.tb target recognition was based on the oxidation signal of the electroactive Methylene Blue (MB) on the surface of the modified GCE using differential pulse voltammetry (DPV) method. It is worth to mention that for the first time Plackett-Burman (PB) screening design and response surface method (RSM) based on central composite design (CCD) was applied as a powerful and an efficient approach to find optimal conditions for maximum M.tb biosensor performance leading to simplicity and rapidity of operation. The proposed DNA biosensor exhibits a wide detection range from 0.25 to 200.0 nM with a low detection limit of 0.141 nM. The performance of designed biosensor for clinical diagnosis and practical applications was revealed through hybridization between DNA probe-modified GCE and extracted DNA from sputum clinical samples.

An Electrochemical Sensor Based on Chalcogenide Molybdenum Disulfide-Gold-Silver Nanocomposite for Detection of Hydrogen Peroxide Released by Cancer Cells

Hydrogen peroxide (H₂O₂) as a crucial signal molecule plays a vital part in the growth and development of various cells under normal physiological conditions. The development of H₂O₂ sensors has received great research interest because of the importance of H₂O₂ in biological systems and its practical applications in other fields. In this study, a H₂O₂ electrochemical sensor was constructed based on chalcogenide molybdenum disulfide-gold-silver nanocomposite (MoS₂-Au-Ag). Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) were utilized to characterize the nanocomposites, and the electrochemical performances of the obtained sensor were assessed by two electrochemical detection methods: cyclic voltammetry and chronoamperometry. The results showed that the MoS₂-Au-Ag-modified glassy carbon electrode (GCE) has higher sensitivity (405.24 µA mM^-1 cm^-2), wider linear detection range (0.05-20 mM) and satisfactory repeatability and stability. Moreover, the prepared sensor was able to detect the H₂O₂ discharge from living tumor cells. Therefore, this study offers a platform for the early diagnosis of cancer and other applications in the fields of biology and biomedicine.