A voltammetric assay for microRNA-25 based on the use of amino-functionalized graphene quantum dots and ss- and ds-DNAs as gene probes

Smart carbon-based sensors for the detection of non-coding RNAs associated with exposure to micro(nano)plastics: an artificial intelligence perspective

Micro(nano)plastics (MNPs) are pervasive environmental pollutants that individuals eventually consume. Despite this, little is known about MNP's impact on public health. In this article, we assess the evidence for potentially harmful consequences of MNPs in the human body, concentrating on molecular toxicity and exposure routes. Since MNPs are present in various consumer products, foodstuffs, and the air we breathe, exposure can occur through ingestion, inhalation, and skin contact. MNPs exposure can cause mitochondrial oxidative stress, inflammatory lesions, and epigenetic modifications, releasing specific non-coding RNAs in circulation, which can be detected to diagnose non-communicable diseases. This article examines the most fascinating smart carbon-based nanobiosensors for detecting circulating non-coding RNAs (lncRNAs and microRNAs). Carbon-based smart nanomaterials offer many advantages over traditional methods, such as ease of use, sensitivity, specificity, and efficiency, for capturing non-coding RNAs. In particular, the synthetic methods, conjugation chemistries, doping, and in silico approach for the characterization of synthesized carbon nanodots and their adaptability to identify and measure non-coding RNAs associated with MNPs exposure is discussed. Furthermore, the article provides insights into the use of artificial intelligence tools for designing smart carbon nanomaterials.

Evaluation of a biosensor-based graphene oxide-DNA nanohybrid for lung cancer

Lung cancer is nowadays among the most prevalent diseases worldwide and features the highest mortality rate among various cancers, indicating that early diagnosis of the disease is of paramount importance. Given that the conventional methods of cancer detection are expensive and time-consuming, special attention has been paid to the provision of less expensive and faster techniques. In recent years, the dramatic advances in nanotechnology and the development of various nanomaterials have led to activities in this context. Recent studies indicate that the graphene oxide (GO) nanomaterial has high potential in the design of nano biosensors for lung cancer detection owing to its unique properties. In the current article, a nano biosensor based on a DNA-GO nanohybrid is introduced to detect deletion mutations causing lung cancer. In this method, mutations were detected using a FAM-labeled DNA probe with fluorescence spectrometry. GO was synthesized according to Hummers' method and examined and confirmed using Fourier Transform Infrared (FT-IR) Spectrometry and UV-vis spectrometry methods and Transmission Electron Microscopy (TEM) images.

Bioanalytical Applications of Graphene Quantum Dots for Circulating Cell-Free Nucleic Acids: A Review

Graphene quantum dots (GQDs) are carbonaceous nanodots that are natural crystalline semiconductors and range from 1 to 20 nm. The broad range of applications for GQDs is based on their unique physical and chemical properties. Compared to inorganic quantum dots, GQDs possess numerous advantages, including formidable biocompatibility, low intrinsic toxicity, excellent dispensability, hydrophilicity, and surface grating, thus making them promising materials for nanophotonic applications. Owing to their unique photonic compliant properties, such as superb solubility, robust chemical inertness, large specific surface area, superabundant surface conjugation sites, superior photostability, resistance to photobleaching, and nonblinking, GQDs have emerged as a novel class of probes for the detection of biomolecules and study of their molecular interactions. Here, we present a brief overview of GQDs, their advantages over quantum dots (QDs), various synthesis procedures, and different surface conjugation chemistries for detecting cell-free circulating nucleic acids (CNAs). With the prominent rise of liquid biopsy-based approaches for real-time detection of CNAs, GQDs-based strategies might be a step toward early diagnosis, prognosis, treatment monitoring, and outcome prediction of various non-communicable diseases, including cancers.

Two-Dimensional Quantum Dot-Based Electrochemical Biosensors

Two-dimensional quantum dots (2D-QDs) derived from two-dimensional sheets have received increasing interest owing to their unique properties, such as large specific surface areas, abundant active sites, good aqueous dispersibility, excellent electrical property, easy functionalization, and so on. A variety of 2D-QDs have been developed based on different materials including graphene, black phosphorus, nitrides, transition metal dichalcogenides, transition metal oxides, and MXenes. These 2D-QDs share some common features due to the quantum confinement effects and they also possess unique properties owing to their structural differences. In this review, we discuss the categories, properties, and synthetic routes of these 2D-QDs and emphasize their applications in electrochemical biosensors. We deeply hope that this review not only stimulates more interest in 2D-QDs, but also promotes further development and applications of 2D-QDs in various research fields.

Development of an electrochemical aptasensor based on Au nanoparticles decorated on metal-organic framework nanosheets and p-biphenol electroactive label for the measurement of aflatoxin B1 in a rice flour sample

This study purposes designing a new aptasensor to detect aflatoxin B1 (AFB1). The AFB1 aptasensor was developed by growing gold nanoparticles on the surface of nickel-based metal-organic framework nanosheets (AuNPs/Ni-MOF) and an electroactive indicator (p-biphenol, PBP). The AFB1 aptamer was immobilized on the AuNPs/Ni-MOF and then hybridized with the complementary DNA (cDNA). PBP was intercalated within the double helix of the cDNA-aptamer. The difference between electrochemical responses of intercalated PBP before and after incubation of AFB1 with the immobilized aptamer was considered as an analytical response. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to monitor the construction processes of the aptasensor. By recording the differential pulse voltammograms of PBP in phosphate buffer (pH 7.0, 0.1 M), the linear range and the detection limit of AFB1 were found to be 5.0 × 10^-3-150.0 ng mL^-1 and 1.0 × 10^-3 ng mL^-1 (S/N = 3), respectively. Finally, the designed aptasensor has been successfully used to measure AFB1 in a rice flour sample with satisfying results. Schematic illustrated the different steps of constructing the electrochemical aptasensor based on Au nanoparticles decorated on Ni-metal-organic framework nanosheets and p-biphenol electroactive label for measuring aflatoxin B1 (AFB1).

Recent Progress in Nanomaterials Modified Electrochemical Biosensors for the Detection of MicroRNA

MicroRNAs (miRNAs) are important non-coding, single-stranded RNAs possessing crucial regulating roles in human body. Therefore, miRNAs have received extensive attention from various disciplines as the aberrant expression of miRNAs are tightly related to different types of diseases. Furthermore, the exceptional stability of miRNAs has presented them as biomarker with high specificity and sensitivity. However, small size, high sequence similarity, low abundance of miRNAs impose difficulty in their detection. Hence, it is of utmost importance to develop accurate and sensitive method for miRNA biosensing. Electrochemical biosensors have been demonstrated as promising solution for miRNA detection as they are highly sensitive, facile, and low-cost with ease of miniaturization. The incorporation of nanomaterials to electrochemical biosensor offers excellent prospects for converting biological recognition events to electronic signal for the development of biosensing platform with desired sensing properties due to their unique properties. This review introduces the signal amplification strategies employed in miRNA electrochemical biosensor and presents the feasibility of different strategies. The recent advances in nanomaterial-based electrochemical biosensor for the detection of miRNA were also discussed and summarized based on different types of miRNAs, opening new approaches in biological analysis and early disease diagnosis. Lastly, the challenges and future prospects are discussed.

Evolution of nucleic acids biosensors detection limit III

This review is an update of two previous ones focusing on the limit of detection of electrochemical nucleic acid biosensors allowing direct detection of nucleic acid target (miRNA, mRNA, DNA) after hybridization event. A classification founded on the nature of the electrochemical transduction pathway is established. It provides an overall picture of the detection limit evolution of the various sensor architectures developed during the last three decades and a critical report of recent strategies.

Femtomolar determination of an ovarian cancer biomarker (miR-200a) in blood plasma using a label free electrochemical biosensor based on L-cysteine functionalized ZnS quantum dots

In the present study, a label-free electrochemical genosensor was designed based on ZnS quantum dots functionalized with l-cysteine (Cys-ZnS-QDs) to detect miR-200a, as a special ovarian cancer biomarker. The Cys-ZnS-QD genosensor was characterized by transmission electron microscopy (TEM), UV-Vis absorption and fluorescence methods. Cys-ZnS-QDs are electrodeposited on the glassy carbon electrode surface and act as a suitable substrate for immobilization of the DNA probe. The effective parameters in the preparation of the genosensor are optimized to improve its analytical performance. The analytical performance of the genosensor has been investigated using electrochemical impedance spectroscopy. Under optimal conditions, the linear range and the detection limit of miR-200a were found to be 1.0 × 10-14 to 1.0 × 10-6 M and 8.4 fM. In addition, the genosensor is used to detect the target complementary miRNA strand from a single-base mismatch miRNA strand. Finally, this label-free electrochemical biosensor was used to detect miR-200a in human plasma without using any amplification method.

Electrochemiluminescence biosensor for microRNA determination based on AgNCs@MoS2 composite with (AuNPs-Semicarbazide)@Cu-MOF as coreaction accelerator

A novel electrochemiluminescence (ECL) biosensor was fabricated for miRNA-162a detection by using silver nanoclusters/molybdenum disulfide (AgNCs@MoS₂) as an ECL material, peroxodisulfate (S₂O₈^2-) as a co-reactant, and semicarbazide (Sem) as a co-reaction accelerator. Firstly, hairpin probe H_a modified on AgNCs@MoS₂/GCE was unfolded based on its hybridization with target microRNA. Then, the unfolded H_a can further be hybridized with another hairpin DNA of H_b on (AuNPs-semicarbazide)@Cu-MOF, resulting in the release of target microRNA, which further causes a cyclic hybridization. This creates more (AuNPs-semicarbazide)@Cu-MOF on the electrode surface, achieving cyclic hybridization signal amplification. Strikingly, due to the presence of Sem, accelerating the reduction of S₂O₈^2- and resulting in the generation of more oxidant intermediates of SO₄^2-, the amount of excited states of Agincreases to further amplify the ECL signal. The biosensor exhibited high sensitivity with a low LOD of 1.067 fM, indicating that the introduction of co-reaction accelerators can provide an effective method for signal amplification. The applicability of this method was assessed by investigating the effect of Pb(II) ion on miRNA-162a expression level in maize seedling leaves. A novel electrochemiluminescence biosensor was fabricated for miRNA-162a detection by using silver nanoclusters/molybdenum disulfide as an ECL material, peroxodisulfate as a co-reactant, and semicarbazide as a co-reaction accelerator.

Experimental and theoretical study for miR-155 detection through resveratrol interaction with nucleic acids using magnetic core-shell nanoparticles

A novel electrochemical nanobiosensor for the detection of miR-155 (as breast cancer biomarker) is introduced . Fe₃O₄NPs@Ag core-shell nanoparticles were synthesized and their shape and characteristics were confirmed by scanning electron microscope (SEM) imaging, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) methods. Synthesized nanoparticles were applied onto the magnetic bar carbon paste electrode and then the amine-modified anti-miR-155 (single-stranded probes) was applied on the modified electrode surface and upon hybridization with target miR-155, resveratrol (RSV) was eventually applied as an electrochemical label on the double-strand oligonucleotide. Differential pulse voltammetry (DPV) of the oxidation peak of RSV was assumed as the final signal by sweeping potential from 0 to 0.6 V (vs. Ag/AgCl). The fabrication process was optimized through a series of experiments and the optimized process was confirmed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The linear range of the fabricated nanobiosensor was 0.5 fM to 1.0 nM and the detection limit was 0.15 fM. The nanobiosensor was able to pass reproducibility and specificity tests using different types of mismatched target sequences.Spiked real samples of human serum were used to confirm that the nanobiosensor enables detection of miR-155 without any significant interferences from other moieties and molecules. Finally, the molecular dynamics simulation of the RSV interaction with single- and double-stranded oligonucleotide was performed and confirmed the preferential binding of RSV to double-stranded DNA; therefore, it can be used as the electrochemical label of DNA and/or miRNA hybridization-based biosensors. Graphical abstract.

Applications of Graphene Quantum Dots in Biomedical Sensors

Due to the proliferative cancer rates, cardiovascular diseases, neurodegenerative disorders, autoimmune diseases and a plethora of infections across the globe, it is essential to introduce strategies that can rapidly and specifically detect the ultralow concentrations of relevant biomarkers, pathogens, toxins and pharmaceuticals in biological matrices. Considering these pathophysiologies, various research works have become necessary to fabricate biosensors for their early diagnosis and treatment, using nanomaterials like quantum dots (QDs). These nanomaterials effectively ameliorate the sensor performance with respect to their reproducibility, selectivity as well as sensitivity. In particular, graphene quantum dots (GQDs), which are ideally graphene fragments of nanometer size, constitute discrete features such as acting as attractive fluorophores and excellent electro-catalysts owing to their photo-stability, water-solubility, biocompatibility, non-toxicity and lucrativeness that make them favorable candidates for a wide range of novel biomedical applications. Herein, we reviewed about 300 biomedical studies reported over the last five years which entail the state of art as well as some pioneering ideas with respect to the prominent role of GQDs, especially in the development of optical, electrochemical and photoelectrochemical biosensors. Additionally, we outline the ideal properties of GQDs, their eclectic methods of synthesis, and the general principle behind several biosensing techniques.

Electrochemical sandwich aptasensor for the carcinoembryonic antigen using graphene quantum dots, gold nanoparticles and nitrogen doped graphene modified electrode and exploiting the peroxidase-mimicking activity of a G-quadruplex DNAzyme

A sandwich-type electrochemical aptasensor has been constructed and applied for sensitive and selective detection of the carcinoembryonic antigen (CEA). The surface of a glassy carbon electrode (GCE) was first modified with nitrogen-doped graphene and then gold nanoparticles and graphene quantum dots electrodeposited on it to obtain an architecture of type GQD/AuNP/NG/GCE. In the next step, the CEA-binding aptamer was immobilized on the modified GCE. Hemin intercalates in the amino-modified hemin aptamer to form a hemin-G-quadruplex (hemin-G4) DNAzyme. The amino modified CEA aptamer II is connected to hemin-G4 by glutaraldehyde (GA) as a linker to produce CEAaptamerII/GA/hemin-G4 (=ApII/GA/DNAzyme). Through a sandwich mode, the ApII/GA/DNAzyme bioconjugates are captured on the modified GCE. Subsequently, the hemin-G4 acts as peroxidase-mimicking DNAzyme and rapidly catalyzes the electroreduction of hydrogen peroxide. The quantitative determination of CEA was achieved by differential pulse voltammetry, best at a working potential of around -0.27 V vs. Ag/AgCl. Under optimized conditions, the assay has a linear response in the 10.0 fg mL^-1 to 200.0 ng mL^-1 CEA concentration range and a lower detection limit of 3.2 fg mL^-1. Graphical abstract Schematic presentation of a sandwich-type electrochemical aptasensor based on nitrogen doped graphene (NG), gold nanoparticles (AuNPs) and graphene quantum dots (GQDs) modified glassy carbon electrode, and the hemin-G4 DNAzyme for femtomolar detection of the carcinoembryonic antigen.

Biomarkers-based Biosensing and Bioimaging with Graphene for Cancer Diagnosis

At the onset of cancer, specific biomarkers get elevated or modified in body fluids or tissues. Early diagnosis of these biomarkers can greatly improve the survival rate or facilitate effective treatment with different modalities. Potential nanomaterial-based biosensing and bioimaging are the main techniques in nanodiagnostics because of their ultra-high selectivity and sensitivity. Emerging graphene, including two dimensional (2D) graphene films, three dimensional (3D) graphene architectures and graphene hybrids (GHs) nanostructures, are attracting increasing interests in the field of biosensing and bioimaging. Due to their remarkable optical, electronic, and thermal properties; chemical and mechanical stability; large surface area; and good biocompatibility, graphene-based nanomaterials are applicable alternatives as versatile platforms to detect biomarkers at the early stage of cancer. Moreover, currently, extensive applications of graphene-based biosensing and bioimaging has resulted in promising prospects in cancer diagnosis. We also hope this review will provide critical insights to inspire more exciting researches to address the current remaining problems in this field.

Graphene oxide with in-situ grown Prussian Blue as an electrochemical probe for microRNA-122

An electrochemical biosensor for microRNA was constructed on the basis of direct growth of electroactive Prussian Blue (PB) on graphene oxide (GO). A mercapto-modified probe DNA that is complementary to the hepatocellular carcinoma biomarker microRNA-122 was firstly anchored on a gold electrode (AuE). Then, GO (with its large surface and multiple active sites) was adsorbed on probe DNA through π-interaction. Subsequently, the PB nanoparticles were directly grown on GO via alternative dipping the electrode in solutions of FeCl₃ and hexacyanoferrate(III). Upon incubation of the resulting electrode with a solution of microRNA-122, the probe DNA on the electrode interacts with microRNA-122 to form a rigid duplex. This results in the release of electroactive PB/GO from the sensing interface and a decrease in current, typically measured at 0.18 V (vs. Ag/AgCl (3 M KCl)). The sensor covers the 10 fM to 10 nM microRNA-122 concentration range and has a 1.5 fM detection limit. The method was successfully applied to the determination of microRNA-122 in real biological samples. Graphical abstract Graphene oxide with in-situ grown Prussian Blue is applied as an electrochemical probe for the analysis of microRNA-122.