Sensitive Electrochemical Biosensor Research Articles

Fabrication of Nanobioengineered Interfaces Utilizing Quaternary Nanocomposite for Highly Efficient and Selective Electrochemical Biosensing of Urea.

Nanobioengineered interfaces have gained attention owing to their small size and high surface area-to-volume ratio for utilization as a platform for highly selective and sensitive biosensing applications owing to the integration of biological molecules with engineered nanomaterials/nanocomposites. In this work, a novel Ag-complex, [(PPh3)2Ag(SCOf)]-based quaternary Ag-S-Zn-O nanocomposites (NCs), was synthesized through an environmentally-friendly process. The results revealed the formation of the NCs with an average crystallite size and particle size of 36.08 and 40.22 nm, respectively. In addition, this is the first study to utilize such NCs synthesized via a single-source precursor method, offering enhanced sensor performance due to their unique structural properties. Further, these NCs were used to fabricate a urease (Ur)/Ag-S-Zn-O NCs/ITO nanobioengineered electrode for precise and sensitive electrochemical biosensing of urea. The interfacial kinetic studies revealed quasi-reversible processes with high electron transfer rates and linear current responses, indicating efficient reaction dynamics. A high diffusion coefficient and low surface concentration suggested a fast diffusion-controlled process, affirming the electrode's potential for rapid and sensitive urea detection. The biosensor demonstrated notable sensing properties such as high sensitivity (12.56 μA mM-1 cm-2) and a low detection limit (0.54 mM). The fabricated bioelectrode was highly selective and reproducible and demonstrated stability for up to 60 days. These results validate the potential of this nanobioengineered interface for next-generation biosensing applications, paving the way for advanced point-of-care diagnostics and real-time health monitoring.

Laser-Induced Graphene for Electrochemical Analysis of Food and Agricultural Contaminants

Carbon-nanomaterial sensors offer promising routes toward low-cost, high-throughput electrochemical sensors. Carbon nanomaterials, such as graphene and carbon nanotube (CNT), have been studied with various fabrication methods to produce sensors, including high-quality thin film graphene and CNT by chemical vapor deposition. However, the complexity and cost associated with their fabrication have hindered their implementation into single-use test strip sensors. Even high-yield mechanical and/or chemical exfoliation of graphene from graphite followed by solution phase printing of electrodes can be costly due to the complexity of ink formulation and the need for post-print annealing requirements. However, laser-induced graphene (LIG) avoids the need to exfoliate graphene from graphite or to create a solution-phase graphene ink by converting sp3 carbon found in carbon-rich substrates into conductive sp2-hybridized carbon found in graphene through a laser scribing technique. The resulting LIG also exhibits a high surface area and is porous with a high density of edge plane sites, which are beneficial for biofunctionalization and heterogeneous charge transport during electrochemical sensing. Furthermore, we have demonstrated that the surface area and wettability of the LIG can be tuned to greatly improve the sensitivity of electrochemical enzymatic biosensors (detection limits down to the picomolar range) and reduce the water layer buildup between the ion-selective membrane and the electrode, which improves the accuracy of the sensor readings. The fabricated LIG electrodes have been used in a wide variety of electrochemical sensing applications, including in food safety (foodborne pathogens and other contaminants), environmental monitoring (agrochemicals), and health monitoring sensors (salivary potassium and lactate, and urinary potassium and ammonium). Different electroanalytical methods are used, including amperometric, potentiometric, coulometric, and impedimetric, to quantify the analytes. We demonstrate how the ISE (ion-selective electrodes) can be functionalized with PVC-based ion-selective membranes for potassium, nitrate, nitrite, ammonium, sodium, and pH in various biological solutions, including soil and water for nutrient/fertilizer monitoring in farm fields. Additionally, we demonstrate how the hydrophilic LIG graphene can be used to create other highly sensitive electrochemical biosensors including enzymatic pesticide biosensors and Salmonella spp. immunosensors. All these electroanalytical sensors were validated in real-world samples and demonstrated to have limits of detection and linear sensing ranges that are relevant to their sensing applications. Results demonstrate the utility of LIG-based sensors for rapid and sensitive electrochemical measurement of contaminants as a readily modified platform for scalable production of electroanalytical devices applied toward point-of-service environmental and food monitoring.

Development of a sensitive ds-DNA/Au NPs/ PGE biosensor for determination of Buprenorphine using electrochemical and molecular dynamic simulation investigation

A sensitive electrochemical DNA biosensor has been developed for the detection of Buprenorphine (Bu), a narcotic pain reliever. To achieve this, double-stranded DNA (ds-DNA) was immobilized on a pencil graphite electrode that was modified with gold nanoparticles (Au NPs/PGE). The gold nanoparticles enhanced the performance of the DNA biosensor. The constructed ds-DNA/Au NPs/ PGE exhibited a linear detection range spanning from 0.05 to 100 μM with an impressive detection limit of 20 nM for Bu detection. Additionally, the DNA biosensor demonstrated good response in real samples evaluations. Finally, the interaction between carbon and gold atoms with DNA was confirmed through molecular dynamics simulation, while the interaction between DNA and the Bu drug was confirmed through molecular docking method. In conclusion, the electrochemical DNA biosensor presented in this study demonstrates exceptional sensitivity and reliability in the detection of buprenorphine. The incorporation of gold nanoparticles, as well as the use of molecular dynamics simulations and docking methods, contributes to a comprehensive understanding of the interactions involved in this detection process.

Light-Driven Electrochemical Biosensing with DNA Origami-Assisted Hybrid Nanoantenna for Fumonisin B1 Monitoring.

The electrochemical detection of biosensors is largely governed by the changes in physical properties of redox probes, which are susceptible to electrode substrate effects, inhibiting sensor sensitivity. In this work, a light-driven electrochemical biosensor based on a hybrid nanoantenna was developed for the sensitive detection of fumonisin B1 (FB1). The hybrid nanoantenna sensing interface was constructed by coupling CdSe quantum dots (QDs)-DNA nanowire and graphdiyne oxide composites loaded with methylene blue and gold nanorods (GDYO-MB-Au NRs) using a tetrahedral DNA nanostructure, which acted as a light-driven unit and an amplification unit, respectively. The hybrid nanoantenna with light-driven properties facilitated the alteration in the chemical properties of MB at the sensing interface; that is, MB was degraded under light illumination. The stripping of the CdSe QDs-DNA nanowire triggered by the binding of FB1 could degrade the light-driven capability, thereby improving the electrochemical signal through depressing MB degradation. Taking advantage of the photodegradation of MB by the hybrid nanoantenna, the developed biosensor reduced the background signal and increased the detection sensitivity. The developed biosensor exhibited a linear detection range from 0.5 fg mL-1 to 10 pg mL-1 and a detection limit down to 0.45 fg mL-1. This strategy shows great promise for the fabrication of highly sensitive electrochemical biosensors.

An ultra-sensitive electrochemical biosensor for circulating tumor DNA utilizing dual enzyme-assisted target recycle and hybridization chain reaction amplification strategies

Circulating tumor DNA (ctDNA) has emerged as a pivotal biomarker for cancers, offering a non-invasive means of detection through liquid biopsies. However, the current methodologies for ctDNA detection often struggle with sensitivity, especially when confronted with ultra-low concentrations. To address this challenge, we have engineered a remarkably sensitive electrochemical biosensor that can detect low concentration of ctDNA. This breakthrough is achieved by integrating a dual enzyme-assisted amplification mechanism with hybridization chain reaction (HCR). In the initial phase, the presence of ctDNA triggers the unfolding of the H2 hairpin structure, resulting in a segment of double-stranded DNA. The subsequent introduction of Klenow (3′→5′ exo-) and nicking endonuclease (Nb.BbvCI) enzymes leads to the abundant production of extended DNA (EXTDNA). This step critically enhances the initial amplification of the target DNA, ensuring superior specificity and selectivity thanks to the synergistic enzymatic activity. EXTDNA efficiently unfolds the H1 hairpin structure immobilized on the gold electrode, which acts as the initiation point for the HCR. Further amplification of the trace target DNA is achieved through an additional H3 and H4 hybrid-mediated HCR. Finally, the differential pulse voltammetry signal of methylene blue is increased significantly. Our results reveal that the developed electrochemical biosensor displays an exceptional linear correlation with ctDNA across concentrations ranging from 10 fM to 20 pM, with an unprecedented detection limit of 2.3 fM (3 s/k). This innovative approach shows immense potential for the ultrasensitive detection of ctDNA, promising broad applications in early cancer detection and monitoring.

Antisense oligonucleotide conjugated gold nanoconstructs-based electrochemical biosensor for detection of SARS-CoV-2

Nanoconstructs of gold nanoparticles (AuNPs) conjugated with SARS-CoV-2 specific antisense oligonucleotides (ASO) have been utilized to develop sensitive electrochemical nucleic acid biosensor for the detection of SARS-CoV-2 RNA. AuNPs were prepared through a one-pot synthesis method by utilizing Poly-L-Lysine (PLL) biopolymer and as synthesised AuNP were characterized by various analytical techniques such as UV–Vis spectroscopy, X-ray Diffraction (XRD) analysis, Fourier Transform Infra-Red spectroscopy (FT-IR), zeta potential, and Transmission Electron Microscopy (TEM). Poly-L-Lysine functionalized AuNPs (PLL-AuNPs) nanoconstructs platform was employed for immobilization of SARS-CoV-2 specific antisense oligonucleotides (ASO-conjugated PLL-AuNPs) via electrostatic interactions. The PLL-AuNPs were drop casted on glassy carbon electrode (GCE) following immobilization of ASO for fabrication of electrochemical biosensor. The ASO-conjugated PLL-AuNPs nanoconstructs were characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The responsiveness of ASO-conjugated PLL-AuNPs nanoconstructs in presence SARS-CoV-2 RNA was monitored using the DPV, SWV and EIS technique, where methylene blue was employed as an electrochemical indicator for DNA-RNA hybridization detection. The biosensor exhibits a detection range for SARS-CoV-2 RNA infection ranging from 0 to 100 nM, with a limit of detection at 30.2 nM. The electrode, modified with ASO-conjugated PLL-AuNPs, was employed for the detection of SARS-CoV-2 RNA from clinical samples collected from COVID-19-positive individuals.

Amplification-free and label-free rapid detection of Staphylococcus aureus using solution-gated graphene transistor-based DNA biosensor with hybridization enhancement by interface engineering

Staphylococcus aureus (S. aureus) is one of the leading causes of foodborne illnesses worldwide, posing a significant risk to food quality and safety. However, conventional detection methods often require complex amplification and labeling procedures, which are time consuming and expensive. In this study, an extremely sensitive electrochemical biosensor using a solution-gated graphene transistor (SGGT) was constructed for the amplification-free and label-free rapid detection of S. aureus by utilizing specific single-stranded DNA (ssDNA) to modify the gold (Au) sensing gate. This modified ssDNA was designed to hybridize with the target S. aureus DNA sequence. Interface engineering of the ssDNA-modified sensing gate via optimization of specific target and probe sequences was proposed to improve its hybridization efficiency. This enabled the sensitive quantitative detection of S. aureus DNA. The resulting biosensor exhibited excellent specificity in distinguishing non-complementary, 3-base/9-base DNA mismatch targets of S. aureus DNA and the specific DNA sequences of other common pathogenic bacteria. It also enabled the rapid detection of extracted target DNA sequences in solution (within 27 min) and had a low limit of detection (LoD) of 10−17 M over a wide linear detection range (10−17–10−8 M). Furthermore, the newly-developed biosensor facilitated the real-time and on-site detection of the S. aureus genome (ATCC 6538) with LoD of 10−17 M (103 CFU/mL) in a portable smart-sensing system. This suggests a promising future for the development of rapid, label-free, and amplification-free detection of foodborne illnesses using low-cost, highly sensitive SGGT DNA biosensors with appropriate functionalization and interface engineering of the sensing electrode.

Electrochemical Biosensor for Point-of-Care Testing of Low-Abundance Biomarkers of Neurological Diseases.

The neurofilament protein light chain (NEFL) is a potential biomarker of neurodegenerative diseases, and interleukin-6 (IL-6) is also closely related to neuroinflammation. Especially, NEFL and IL-6 are the two most low-abundance known protein markers of neurological diseases, making their detection very important for the early diagnosis and prognosis prediction of such kinds of diseases. Nevertheless, quantitative detection of low concentrations of NEFL and IL-6 in serum remains quite difficult, especially in the point-of-care test (POCT). Herein, we developed a portable, sensitive electrochemical biosensor combined with smartphones that can be applied to multiple scenarios for the quantitative detection of NEFL and IL-6, meeting the need of the POCT. We used a double-antibody sandwich configuration combined with polyenzyme-catalyzed signal amplification to improve the sensitivity of the biosensor for the detection of NEFL and IL-6 in sera. We could detect NEFL as low as 5.22 pg/mL and IL-6 as low as 3.69 pg/mL of 6 μL of serum within 2 h, demonstrating that this electrochemical biosensor worked well with serum systems. Results also showed its superior detection capabilities over those of high-sensitivity ELISA for serum samples. Importantly, by detecting NEFL and IL-6 in sera, the biosensor showed its potential for the POCT model detection of all known biomarkers of neurological diseases, making it possible for the mass screening of patients with neurodegenerative diseases.

Graphene quantum dots mediated acrylamide biosensing

Acrylamide (AA) is an unwanted food processing contaminant produced during cooking at high temperatures through the Maillard reaction between asparagine and reducing sugars or reactive carbonyls. In humans, it causes significant neurotoxicity, genotoxicity, and possible carcinogenicity. AA is categorized as a ‘Group 2A’ carcinogen by the International Agency for Research on Cancer (IARC). Bread, biscuits, and potato crisps are examples of foods heavy in starch that contain significant quantities of AA. Consequently, the detrimental effects of AA on human health make determining its quantitative content a crucial matter. Here, by immobilizing Hemoglobin nanoparticles (HbNPs) onto graphene quantum dots (GQDs) decorated pencil graphite (PG) electrode, we have developed a highly sensitive electrochemical biosensor for the detection of AA. Using cyclic voltammetry (CV), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS), the developed working electrode (HbNPs/GQDs/PG) was examined at different stages of its preparation. The ideal pH and temperature for the fabricated biosensor were 5.0 and 35 °C, respectively and the biosensor demonstrated an acceptable level of selectivity, sensitivity, and stability along with a broad linear range (10 nM to 120 nM) and a low detection limit of 2.70 nM. The suggested strategy made use of less costly raw materials to ensure that it should be both effective and environmentally friendly. The sensor was effectively used to measure the amounts of AA in potato crisp samples.

Facile synthesis of novel porphyrin-based covalent organic frameworks integrated with Au nanoparticles for highly sensitive detection of organophosphorus pesticide residues

Organophosphorus pesticides (OPs) residues in agricultural products such as vegetables, fruits, and grains pose a threat to food safety and human health. In this work, a novel and highly sensitive electrochemical biosensor was developed for OPs residues detection in real sample, based on the immobilization of acetylcholinesterase (AChE) by electrostatic adsorption on a glassy carbon electrode (GCE) modified with composite nanomaterials of porphyrin-based covalent organic frameworks (p-COFs) loaded by gold nanoparticles (AuNPs) and poly (diallyldimethylammonium chloride) (PDDA). Due to the synergistic effect of p-COFs, AuNPs and PDDA, the fabricated biosensor displayed the remarkable properties with the high electrocataytic activity, and excellent biocompatibility, resulting in a significant signal amplification of as-prepared biosensor. Under optimized conditions, the biosensor showed excellent sensing performances for the detection of methyl parathion (MP), with wide linear ranges from 1.9 × 10−9–3.8 × 10−5 M and a low detection limit as low as 2.3 × 10−10 M, as well as the satisfactory selectivity, excellent reproducibility, anti-interference properties and good stability. It was also successfully applied to the monitoring of MP content in vegetables and fruits, which may be explore a new opportunity for the potential utilization in analysis field.

Electrochemical sensing of cortisol by gold nanoparticle incorporated carboxylated graphene oxide based molecularly imprinted polymer

In this work, we report a simple electrochemical biosensor for cortisol (Cor) detection using a molecularly imprinted polymer (MIP). MIP was prepared by graft copolymerization method on allylated gold nanoparticle (Au) incorporated carboxylated graphene oxide (allylated Au/GO-COOH) polymerized along with the template molecule Cor. Cor is one of the important corticosteroid hormones in human physiology. Cor, the stress hormone, is a steroid hormone that comes under the class of glucocorticoid hormones and is produced as a part of our body’s stress response. This Cor imprinted polymer (Cor-MIP) was chosen to modify the working glassy carbon electrode surface. Thereby developing a highly selective and sensitive electrochemical biosensor. Electrochemical Impedance Spectroscopy and Cyclic Voltammetry explored the electrochemical properties of the developed electrochemical biosensor. The investigation reports from the electrochemical studies revealed that the current value increases proportionally with increasing concentration of Cor. This confirmed the excellent electrocatalytic activity of the prepared Cor-MIP based biosensor toward Cor. The nanomaterials as well as the electroactive sites on Cor-MIP together enhancing the electron transfer rate and lower detection. Differential Pulse Voltammetry is used to find the limit of detection and quantification, and were obtained as, 0.61 × 10−14 M and 2.02 × 10−14 M, respectively. With excellent specificity, stability, and selectivity, this newly developed electrochemical biosensor has been successfully used for Cor measurements in human blood serum samples.

Tailored electrochemical biosensor with poly-diallydimethylammonium chloride-functionalised multiwalled carbon nanotubes/gold nanoparticles/manganese dioxide, and haemoglobin for sensitive hydrogen peroxide detection

A very sensitive electrochemical biosensor, with haemoglobin (Hb) as its basis, has been created to quantify hydrogen peroxide (H2O2), an essential marker in environmental monitoring, food safety, and medical diagnosis. The sensor uses a simple, eco-friendly preparation method. Hb was immobilised on manganese dioxide nanostructure/gold nanoparticles/poly-diallydimethylammonium chloride-functionalised multiwalled carbon nanotubes (PDDA-MWCNT/AuNP/MnO2), characterised using various techniques: amperometry, voltammetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Nafion was used as a binder membrane to preserve the biological and electrochemical properties of the protein on the modified electrode. In comparison to earlier research, the novel biosensor had a lower detection limit (1.83 μM) and a limit of quantification (6.11 μM) (S/N = 3) for H2O2. It also exhibited notable reproducibility, long-term stability, and repeatability. It was effectively used to measure the amount of H2O2 in cow milk and orange juice, yielding recoveries in the order of 98.90–99.53 % with RSDs less than 5.0 %, which makes it a promising biosensor for food control.

Nucleic acid aptamer-based electrochemical sensor for the detection of serum P-tau231 and the instant screening test of Alzheimer's disease.

The instant screening of patients with a tendency towards developing Alzheimer's disease (AD) is significant for providing preventive measures and treatment. However, the current imaging-based technology cannot meet the requirements in the early stage. Developing biosensor-based liquid biopsy technology could be overcoming this bottleneck problem. Herein, we developed a simple, low-cost, and sensitive electrochemical aptamer biosensor for detecting phosphorylated tau protein threonine 231 (P-tau231), the earliest and one of the most efficacious abnormally elevated biomarkers of AD. Gold nanoparticles (AuNPs) were electrochemically synthesized on a glassy carbon electrode as the transducer, exhibiting excellent conductivity, and were applied to amplify the electrochemical signal. A nucleic acid aptamer was designed as the receptor to capture the P-tau231 protein, specifically through the formation of an aptamer-antigen complex. The proposed biosensor showed excellent sensitivity in detecting P-tau 231, with a broad linear detection range from 10 to 107pg/mL and a limit of detection (LOD) of 2.31pg/mL. The recoveries of the biosensor in human serum ranged from 97.59 to 103.26%, demonstrating that the biosensor could be used in complex practical samples. In addition, the results showed that the developed biosensor has good repeatability, reproducibility, and stability, which provides a novel method for the early screening of AD.

Sensitive electrochemical biosensor for rapid detection of sEV-miRNA based turbo-like localized catalytic hairpin assembly

Small extracellular vesicle-associated microRNAs (sEV-miRNAs) have emerged as critical biomarkers for cancer diagnosis, yet the rapid detection of these low-abundance molecules in clinical samples remains a formidable challenge. Herein, a simple turbo-like localized catalytic hairpin assembly (TL-CHA) was proposed for sEV-miR-1246 measurement. This electrochemical sensor achieves dual localization through the ingeniously use of AuNPs and DNA nanowires, which provides rich sites for CHA cascade amplification, significantly enhancing the effective reaction and amplify the detection response. Leveraging this innovative design, this biosensor demonstrated the ability to detect sEV-miRNA at concentrations as low as 5.24 aM in a time frame of 30 min. The precision of the measurements was validated through reverse transcription quantitative polymerase chain reaction. Furthermore, the sensor was used for analyzing plasma samples from gastric cancer patients yielded AUC values of 0.973 for all stages and 0.945 for early stages. This demonstrates the sensor's robust performance in both the staging diagnosis and early screening of gastric cancer. Therefore, this platform has great potential for the clinical cancer diagnosis.

Electrospun EU/HPMC nanofibers decorated by ZIF-8 nanoparticle as the advanced electrochemical biosensor modifier for sensitive and selective detection of c-MET cancer biomarker in human plasma sample

This research presents a selective and sensitive electrochemical biosensor for the detection of the mesenchymal–epithelial transition factor (c-MET). The biosensing is based on a modification of the SPCE (screen-printed carbon electrode) with the electrospun nanofiber containing eudragit (EU), hydroxypropyl methylcellulose (HPMC), and Zeolite imidazolate frameworks (ZIF-8) nanoparticles. EU/HPMC/ZIF-8 nanofibers have presented a high capability of electron transfer, and more active surface area than bare SPCE due to synergistic effects between EU, HPMC, and ZIF-8. On the other hand, EU/HPMC nanofibers provided high porosity, flexible structures, high specific surface area, and good mechanical strength. The presence of ZIF-8 nanoparticles improved the immobilization of anti-c-MET on the modified SPCE and also resulted in increasing the conductivity. By c-MET incubation on the modified SPCE, c-MET was connected to anti-c-MET, and consequently the electrochemical signal of [Fe(CN)6]3-/4- as the anion redox probe was reduced. In order to investigate the structural and morphological characteristics and elemental composition of electrospun nanofibers, various characterization methods including FE-SEM, XRD, FTIR, and EDS were used. Under optimum conditions with a working potential range −0.3−0.6 V (vs. Ag/AgCl), linear range (LR), correlation coefficient (R2), sensitivity, and limit of detection (LOD) were acquired at 100 fg/mL-100 ng/mL, 0.9985, 53.28 μA/cm2.dec, and 1.28 fg/mL, respectively. Moreover, the mentioned biosensor was investigated in a human plasma sample to determine c-MET and showed ideal results including reproducibility, stability, and good selectivity against other proteins.

Electrochemical Detection of Bisphenol A Based on Gold Nanoparticles/Multi-Walled Carbon Nanotubes: Applications on Glassy Carbon and Screen Printed Electrodes.

Bisphenol A (BPA) has been classified as an endocrine-disrupting substance that may cause adverse effects on human health and the environment. The development of simple and sensitive electrochemical biosensors is crucial for the rapid and effective quantitative determination of BPA. This work presents a study on electrochemical sensors utilizing gold nanoparticle-modified multi-walled carbon nanotubes (CNT/AuNPs). Glassy carbon electrodes (GCEs) and screen-printed electrodes (SPEs) were conveniently modified and used for BPA detection. AuNPs were electrodeposited onto the CNT-modified electrodes using the galvanostatic method. The electrodes were properly modified and characterized by using Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance analysis (EIS). The electrochemical response of the sensors was studied using differential pulse voltammetry (DPV) and constant potential amperometry (CPA) for modified GCE and SPE electrodes, respectively, and the main analytical parameters were studied and optimized. Problems encountered with the use of GCEs, such as sensor degradation and high limit of detection (LOD), were overcome by using modified SPEs and a flow injection device for the measurements. Under this approach, an LOD as low as 5 nM (S/N = 3) was achieved and presented a linear range up to 20 μM. Finally, our investigation addressed interference, reproducibility, and reusability aspects, successfully identifying BPA in both spiked and authentic samples, including commercial and tap waters. These findings underscore the practical applicability of our method for accurate BPA detection in real-world scenarios. Notably, the integration of SPEs and a flow injection device facilitated simplified automation, offering an exceptionally efficient and reliable solution for precise BPA detection in water analysis laboratories.

Target-induced activation of dual DNAzyme recycling amplifications for sensitive electrochemical fat mass and obesity-associated protein assay

The fat mass and obesity-associated protein (FTO) is vital for modulating dynamic reversible process of N6-methyladenosine (m6A) level in the nucleus and the abnormal expression of FTO correlates with generation and development of Alzheimer's disease, obesity and several cancers. The sensitive detection of FTO is therefore of significance for diagnosis of FTO-related diseases. In this work, on the basis of the demethylation enzyme capability of FTO and the dual Mg2+-dependent DNAzyme recycled signal magnification strategy, establishment of a highly sensitive electrochemical FTO biosensor is described. The target FTO molecules catalyze the demethylation of m6A-modified sequences to form effective cleavage substrates for the MboI endonuclease, leading to the release of active DNAzyme sequences to trigger subsequent dual DNAzyme recycling cycles. Many methylene blue-tagged ssDNA sequences can thus be yielded via the DNAzyme amplifications and captured on the sensor electrode to generate highly amplified currents for detecting FTO in range of 0.04 pM to 10 nM with 6.11 fM detection limit. Additionally, the sensor demonstrates high selectivity and is able to be used for detecting cell lysate FTO, showing its potential for the diagnosis and study of FTO-related diseases for various application purposes.

A sensitive electrochemical biosensor for detection of carbaryl based on hollow covalent-organic frameworks-gold nanoparticles nanospheres

Carbaryl as an important insecticide is always used in agricultures to achieve higher yields. So, rapid detection of carbaryl residues in agricultural products is very necessary due to its potential harm to human beings. Herein, a hollow covalent-organic frameworks (HCOFTFPB-DBD) gold nanoparticles (AuNPs) nanospheres was used to construct a sensitive electrochemical carbaryl biosensor. The surface of electrode modified by HCOFTFPB-DBD-AuNPs nanospheres was negatively charged and repelled the [Fe(CN)6]3-/4-. The acetylcholinesterase (AChE) immobilized on HCOFTFPB-DBD-AuNPs nanospheres catalyzed the hydrolysis of acetylcholine chloride to thiocholine (TCh). The obtained positively charged TCh was adsorbed on the electrode surface by Au-S, which made the electrode surface positively charged to adsorb the negatively charged [Fe(CN)6]3-/4-, showing enhanced oxidation current of [Fe(CN)6]3-/4-. After carbaryl was added, the oxidation current of [Fe(CN)6]3-/4- deceased because ChE activity were inhibited by carbaryl. So, the sensitive detection of carbaryl was achieved at a low potential, which resulted in a high selectivity. The biosensor had a detection limit of 0.38 μM, a linear range of 1.10 μM-40.0 μM, a sensitivity of 0.00863 mA μM−1 and better performance in actual sample.

Ultrahigh peroxidase-like catalytic performance of Cu–N4 and Cu–N4S active sites-containing reduced graphene oxide for sensitive electrochemical biosensing

Carbon-based nanozymes possessing peroxidase-like activity have attracted significant interest because of their potential to replace native peroxidases in biotechnology. Although various carbon-based nanozymes have been developed, their relatively low catalytic efficiency needs to be overcome to realize their practical utilization. Here, inspired by the elemental uniqueness of Cu and the doped elements N and S, as well as the active site structure of Cu-centered oxidoreductases, we developed a new carbon-based peroxidase-mimicking nanozyme, single-atom Cu-centered N- and S-codoped reduced graphene oxide (Cu-NS-rGO), which preserved many Cu–N4 and Cu–N4S active sites and showed dramatically high peroxidase-like activity without any oxidase-like activity, yielding up to 2500-fold higher catalytic efficiency (kcat/Km) than that of pristine rGO. The high catalytic activity of Cu-NS-rGO might be attributed to the acceleration of electron transfer from Cu single atom as well as synergistic effects from both Cu–N4 and Cu–N4S active sites, which was theoretically confirmed by Gibbs free energy calculations using density functional theory. The prepared Cu-NS-rGO was then used to construct an electrochemical bioassay system for detecting choline and acetylcholine by coupling with the corresponding oxidases. Using this system, both target molecules were selectively determined with high sensitivity that was sufficient to clinically determine their levels in physiological fluids. Overall, this study will facilitate the development of nanocarbon-based nanozymes and their electrochemical biosensing applications, which can be extended to the development of miniaturized devices in point-of-care testing environments.

Sensitive electrochemical biosensor for Ustilaginoidea Virens short-stranded DNA segment via higher-ordered G-quadruplex multimerization induced by LAMP/H+-responsive i-motif folding

By using variable loop-mediated isothermal amplification byproduct H+ ions (vLAMP/H+) as signal transducer, exploring the electrochemical assay of short-stranded DNA segment related to U. virens (uDNA, 21-nt) is intriguing. Herein, we report the first design of a sensitive electrochemical biosensor for uDNA as targeting input promoter of vLAMP, for which a discernible template hairpin and a precursor hairpin are well-designed. The specific recognition and complementary hybridization among them form a double-dumbbell DNA structure tethering two stem-loop motifs that is served as template precursor to operate vLAMP for DNA+1 polymerization via nucleotide incorporation, generating vLAMP/H+ to modulate pH-responsive i-motif folding of a C-rich strand. A ferrocene-tagged G-rich strand is dehybridized and incubated in modified electrode surface including an amino-labeled G-rich strand that adopts compact G-quadruplex (G4) conformation. This G4, as an initiator, guides the ‘head-to-tail’ π-π stacking of electroactive tags for developing higher-ordered wire-like G4 multimers (G4W), which are stably held together via interquadruplex multimerization. No involving additional nucleic acid amplifiers, numerous electroactive mediators are repetitively cascaded, thereby significantly amplifying the current readout signal and achieving sensitive electrochemical detection of U. virens. Benefited from simple and rapid vLAMP/H+-G4W route, our assay strategy would provide a new paradigm to create applicable electrochemical biosensors for diverse short-stranded DNA biomarkers by altering LAMP operation modes readily.