Amperometric aptasensor with sandwich-type architecture for troponin I based on carboxyethylsilanetriol-modified graphene oxide coated electrodes

Magnetically controlled graphene field-effect transistor biosensor for highly sensitive detection of cardiac troponin I

Herein, we have constructed a magnetic graphene field-effect transistor biosensor (MGFETs) for highly sensitive detection of cardiac troponin I (CTNI). Graphene films transferred to ITO conductive glass as conductive channels. CTNI aptamer was immobilized onto the graphene film via 1-pyrene-butanoic acid succinimidyl ester (PBASE) to capture CTNI. Magnetic nanobeads (MBs) modified with CTNI antibody were added to the reaction chamber to form an aptamer/CTNI/antibody/magnetic nanobeads sandwich-type complex. We found that the magnetic force exerted on the complex leads to an impedance change of the graphene film. The reason for this result is that the magnetic field exerts an influence on the MBs, causing CTNI aptamer strand to bend, resulting in a change in the distance between the double conductive layers of the graphene film surface and the test solution. With periodic sampling integration, different concentrations of CTNI can be detected with high sensitivity. Due to the stringent recognition capability and high affinity between the CTNI aptamer and CTNI, MGFETs have the potential to detect various types of proteins. Furthermore, MGFETs also have the potential to be utilized for the detection of DNA or specific cells in the future.

Recent advancements of nanomodified electrodes - Towards point-of-care detection of cardiac biomarkers

The increasing number of deaths from cardiovascular diseases has become a substantial concern in both developed and underdeveloped countries. Rapid and on-site monitoring of this disease is urgently important to control, prevent and make awareness of public health. Recently, a lot of focus has been placed on nanomaterials and modify these nanomaterials have been explored to detect cardiac biomarkers. By implementing biosensors that are modified with novel recognition elements and more stable nanomaterials, the use of electrochemistry for point-of-care devices is more realistic every day. This review focuses on the current state of nanomaterials conjugated biorecognition elements (enzyme integrated with nanomaterials, antibody conjugated nanomaterials and aptamer conjugated nanomaterials) for electrochemical cardiovascular disease detection. Specifically, a lot of attention has been given to the trends toward more stable biosensors that have increased the potential to be used as point-of-care devices for the detection of cardiac biomarkers due to their high stability and specificity. Moreover, the recent progress on biomolecule-free electrochemical nanosensors for cardiovascular disease detection has been considered. At last, the possibility and drawbacks of some of these techniques for point-of-care cardiac device development in the future have been discussed.

A Review on Aptamers Selection and Application in Heart Diseases Diagnosis

Biomarkers detection and quantification in biological fluids play a key role in the screening, diagnosing and treating several diseases. Recently, a large number of aptamers have been selected and applied for the sensing of different biomarkers. Combined with different transducers, aptamers provide simple and rapid tools that allow highly sensitive and selective detection. Cardiology requires an accurate assessment of cardiac biomarkers for a complete diagnosis of cardiovascular diseases. The analysis is generally performed by immunoassays using antibodies as biorecognition elements. This review paper focuses on using aptamers as a promising alternative for antibodies in cardiac biomarkers biosensing. First, the different aptamers specific to the most important cardiac biomarkers are Troponin I, the peptide of B-type natriuretic peptide and myoglobin. Then, in the second part, we overview the electrochemical aptasensors principle and characteristics reported in the literature in the last five years.

A High-Performance Self-Supporting Electrochemical Biosensor to Detect Aflatoxin B1

High-performance electrochemical biosensors for the rapid detection of aflatoxin B1 (AFB₁) are urgently required in the food industry. Herein, a multi-scaled electrochemical biosensor was fabricated by assembling carboxylated polystyrene nanospheres, an aptamer and horseradish peroxidase into a free-standing carbon nanofiber/carbon felt support. The resulting electrochemical biosensor possessed an exceptional performance, owing to the unique structures as well as the synergistic effects of the components. The 3D porous carbon nanofiber/carbon felt support served as an ideal substrate, owing to the excellent conductivity and facile diffusion of the reactants. The integration of carboxylated polystyrene nanospheres with horseradish peroxidase was employed as a signal amplification probe to enhance the electrochemical responses via catalyzing the decomposition of hydrogen peroxide. With the aid of the aptamer, the prepared sensors could quantitatively detect AFB₁ in wine and soy sauce samples via differential pulse voltammetry. The recovery rates of AFB₁ in the samples were between 87.53% and 106.71%. The limit of detection of the biosensors was 0.016 pg mL^-1. The electrochemical biosensors also had excellent sensitivity, reproducibility, specificity and stability. The synthetic strategy reported in this work could pave a new route to fabricate high-performance electrochemical biosensors for the detection of mycotoxins.

Sandwich-type electrochemical aptasensor based on Au-modified conductive octahedral carbon architecture and snowflake-like PtCuNi for the sensitive detection of cardiac troponin I

The cardiac troponin I (cTnI) detection is increasingly significant given its promising value in the clinical acute myocardial infarction diagnosis. Here a sensitive sandwich-type cTnI electrochemical aptasensor was developed by using zirconium-carbon loaded with Au (Au/Zr-C) as electrode-modified material and snowflake-like PtCuNi catalyst as label material. The Au/Zr-C was prepared from a carbonation process and a reduction step. The PtCuNi was synthesized by a one-pot hydrothermal reaction. On the one hand, due to its many merits of large effective area, rich pores, high degree of graphitization, the assistance of Au, the Au/Zr-C exhibited remarkable electronic conductivity but low catalytical capacity, thus improving the electrochemical property but lowing the background signal of electrode. On the other hand, because of its accessible active sites of the special snowflake-like structure and the synergy of three elements, the PtCuNi catalyst presented excellent catalytic activity and improved stability compared to binary alloy. The recognition reactions were achieved by stepwise incubation of aptamer 1, cTnI, and aptamer 2-PtCuNi (denoted as Apt2-label) on the Au/Zr-C-modified electrode. The electrocatalytic signals of the immobilized Apt2-label towards the H₂O₂ reduction were recorded in all tests for cTnI analysis. Consequently, this cTnI aptasensor exhibited excellent performance involving a wide linear range of 100 ng mL^-1 to 0.01 pg mL^-1 with a detection limit of 1.24 × 10^-3 pg mL^-1 (S/N = 3), good selectivity, satisfying reproducibility, outstanding stability, and good recovery.

Development of 2D graphene oxide sheets-based voltammetric sensor for electrochemical sensing of fungicide, carbendazim

Incorporating new pollutants and environmental pollution has become a formidable issue as new pollutants are introduced into it and have become a significant concern in recent years. Detection of such pollutants needs a susceptible, selective, and cost-effective sensor that can sense their presence and quantify them at a trace level. In the present study, we have designed a 2D graphene oxide (GO)-based glassy carbon electrode (GCE) electrochemical sensor (GO/GCE) and utilized it as a sensing material for the detection and determination of CRZ. The voltammetric behavior of CRZ was studied using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. The SWV was applied to quantify and analyze CRZ in actual samples. A better response of CRZ was noticed at GO/GCE when phosphate buffer solution of pH 4.2 was used as a supporting electrolyte for to experiment. The SWV technique achieved trace-level detection of CRZ. A linearity plot was obtained for the concentration range of 1.0 × 10^-7 M to 2.5 × 10^-4 M with a limit of detection of 1.38 × 10^-8 M. The selectivity of the modified sensor was verified by the interference study of metal ions and other pesticides with CRZ. The agricultural and environmental significance of the developed method was successfully tested by estimating CRZ in water and soil samples.

Recent Advances in Electrochemical Aptasensors for Detection of Biomarkers

The early diagnosis of diseases is of great importance for the effective treatment of patients. Biomarkers are one of the most promising medical approaches in the diagnosis of diseases and their progress and facilitate reaching this goal. Among the many methods developed in the detection of biomarkers, aptamer-based biosensors (aptasensors) have shown great promise. Aptamers are promising diagnostic molecules with high sensitivity and selectivity, low-cost synthesis, easy modification, low toxicity, and high stability. Electrochemical aptasensors with high sensitivity and accuracy have attracted considerable attention in the field of biomarker detection. In this review, we will summarize recent advances in biomarker detection using electrochemical aptasensors. The principles of detection, sensitivity, selectivity, and other important factors in aptasensor performance are investigated. Finally, advantages and challenges of the developed aptasensors are discussed.

Electrochemical aptasensor based on anisotropically modified (Janus-type) gold nanoparticles for determination of C-reactive protein

Novel Janus nanoparticles based on Au colloids anisotropically modified with polyamidoamine dendrons were prepared though a masking/toposelective modification approach. These nanomaterials were further functionalized with horseradish peroxidase on the dendritic face and provided on the opposite metal surface with a ssDNA aptamer for C-reactive protein (CRP). The resulting nanoparticles were employed as biorecognition/signaling elements to construct an amperometric aptasensor with sandwich-type architecture for the specific detection of this cardiac biomarker. To do this, screen-printed carbon electrodes modified with electrodeposited Au nanoparticles and functionalized with anti-CRP aptamers were used as transduction interface. The aptasensor was employed for the amperometric detection of CRP (working potential: - 200 mV vs pseudo-Ag/AgCl) in the broad range from 10 pg·mL^-1 to 1.0 ng·mL^-1 with a detection limit of 3.1 pg·mL^-1. This electroanalytical device also showed good specificity, reproducibility (RSD = 9.8%, n = 10), and stability and was useful to quantify CRP in reconstituted human serum samples, with a RSD of 13.3%.

Graphene-Based Biosensors for Molecular Chronic Inflammatory Disease Biomarker Detection

Chronic inflammatory diseases, such as cancer, diabetes mellitus, stroke, ischemic heart diseases, neurodegenerative conditions, and COVID-19 have had a high number of deaths worldwide in recent years. The accurate detection of the biomarkers for chronic inflammatory diseases can significantly improve diagnosis, as well as therapy and clinical care in patients. Graphene derivative materials (GDMs), such as pristine graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO), have shown tremendous benefits for biosensing and in the development of novel biosensor devices. GDMs exhibit excellent chemical, electrical and mechanical properties, good biocompatibility, and the facility of surface modification for biomolecular recognition, opening new opportunities for simple, accurate, and sensitive detection of biomarkers. This review shows the recent advances, properties, and potentialities of GDMs for developing robust biosensors. We show the main electrochemical and optical-sensing methods based on GDMs, as well as their design and manufacture in order to integrate them into robust, wearable, remote, and smart biosensors devices. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers with improved sensitivity, reaching limits of detection from the nano to atto range concentration.

Horseradish peroxidase-triggered direct in situ fluorescent immunoassay platform for sensing cardiac troponin I and SARS-CoV-2 nucleocapsid protein in serum

Direct in situ fluorescent enzyme-linked immunosorbent assay (ELISA) is rarely investigated and reported. Herein, a direct in situ high-performance HRP-labeled fluorescent immunoassay platform was constructed. The platform was developed based on a rapid in situ fluorogenic reaction between Polyethyleneimine (PEI) and p-Phenylenediamine (PPD) analogues to generate fluorescent copolymer nanoparticles (FCNPs). The formation mechanism of FCNPs was found to be the oxidation of •OH radicals, which was further proved by nitrogen protection and scavenger of •OH radicals. Meantime, the fluorescence wavelength of FCNPs could be adjusted from 471 to 512 nm by introducing various substitution groups into the PPD structure. Using cardiac troponin I (cTnI) and SARS-CoV-2 nucleocapsid protein (N-protein) as the model antigens, the proposed fluorescent ELISA exhibited a wide dynamic range of 5-180 ng/mL and a low limit of detection (LOD) of 0.19 ng/mL for cTnI, and dynamic range of 0-120 ng/mL and a LOD of 0.33 ng/mL for SARS-CoV-2 N protein, respectively. Noteworthy, the proposed method was successful applied to evaluate the cTnI and SARS-CoV-2 N protein levels in serum with satisfied results. Therefore, the proposed platform paved ways for developing novel fluorescence-based HRP-labeled ELISA technologies and broadening biomarker related clinical diagnostics.

Electrochemical Microfluidic Paper-Based Aptasensor Platform Based on a Biotin-Streptavidin System for Label-Free Detection of Biomarkers

Timely and rapid detection of biomarkers is extremely important for the diagnosis and treatment of diseases. However, going to the hospital to test biomarkers is the most common way. People need to spend a lot of money and time on various tests for potential disease detection. To make the detection more convenient and affordable, we propose a paper-based aptasensor platform in this work. This device is based on a cellulose paper, on which a three-electrode system and microfluidic channels are fabricated. Meanwhile, novel nanomaterials consisting of amino redox graphene/thionine/streptavidin-modified gold nanoparticles/chitosan are synthesized and modified on the working electrode of the device. Through the biotin-streptavidin system, the aptamer whose 5'end is modified with biotin can be firmly immobilized on the electrode. The detection principle is that the current generated by the nanomaterials decreases proportionally to the concentration of targets owing to the combination of the biomarker and its aptamer. 17β-Estradiol (17β-E2), as one of the widely used diagnostic biomarkers of various clinical conditions, is adopted for verifying the performance of the platform. The experimental results demonstrated that this device enables the determination of 17β-E2 in a wide linear range of concentrations of 10 pg mL^-1 to 100 ng mL^-1 and the limit of detection is 10 pg mL^-1 (S/N = 3). Moreover, it enables the detection of targets in clinical serum samples, demonstrating its potential to be a disposable and convenient integrated platform for detecting various biomarkers.