A Highly Sensitive Electrochemical DNA Biosensor from Acrylic-Gold Nano-composite for the Determination of Arowana Fish Gender

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.

Electrochemical Biosensor Based on l-Arginine and rGO-AuNSs Deposited on the Electrode Combined with DNA Probes for Ultrasensitive Detection of the Gastric Cancer-Related PIK3CA Gene of ctDNA

Gene biomarkers of circulating tumor DNA (ctDNA) in liquid biopsies have been explored for use in the precise diagnosis of tumors. There is a great clinical need to realize the ultrasensitive detection of gene biomarkers in ctDNA. Here we reported that an ultrasensitive label-free biosensor was developed for the detection of the gastric cancer-related PIK3CA gene of ctDNA in peripheral blood. The polymeric l-arginine and graphene oxide-wrapped gold nanostars (rGO-AuNSs) were prepared and deposited on the glass electrode. The capturing DNA probes for the PIK3CA gene were prepared and successfully immobilized on the rGO-AuNS-modified electrode surface via π-π interaction among the rGO-AuNS composites and DNA probes. The resultant electrochemical sensor was effectively applied to detect the PIK3CA gene of ctDNA via the hybridization between the capturing DNA probe and ctDNA, the result of which showed that the biosensor exhibited desirable sensitivity, stability, and a wider dynamic response in a ctDNA concentration range from 1.0 × 10^-20 to 1.0 × 10^-10 M (R² = 0.997). Moreover, the low limit of detection of 1.0 × 10^-20 M (S/N = 3) indicates the biosensor owns satisfactory detection sensitivity. Fourteen PIK3CA genes and two PIK3CA gene mutations were detected in 60 clinical ctDNA samples of gastric cancer patients by using the developed biosensor. In conclusion, this ultrasensitive label-free electrochemical biosensor possesses a significant application prospect in the detection of the PIK3CA gene in ctDNA and in early screening for gastric cancer in the near future.

An electrochemical biosensor for the rapid genetic identification of Musang King durian

More than 200 different cultivars of durian exist worldwide but Durio zibethinus or Musang King (MK) is the most premium and prized durian fruit among the recommended varieties. Early identification of this premium variety is critical to protect from non-authentic MK durian cultivars. However, the MK variety's morphological traits are nearly identical to other varieties. Currently, the identification of durian varieties is mostly performed via evaluation of leaf shape, fruit shape, aroma, taste and seed shape and this requires trained personnel for the morphology observation. To enable the rapid identification of the MK variety, PCR amplification of ten durian varieties using six gene candidates from the chloroplast genome was first performed to obtain DNA probes that were specific to the MK durian variety. PCR amplification of ten durian varieties using primers designed confirmed that the nadhA gene sequence showed an obvious difference in the MK variety from other durian varieties. The unique sequence of MK was used as a DNA probe to develop an electrochemical biosensor for the direct identification of the MK durian variety. The electrochemical biosensor was based on the hybridization response of the immobilized DNA probe with the target DNA from the MK variety and was monitored via differential pulse voltammetry technique. Under optimal conditions, the DNA electrochemical biosensor showed a low detection limit at 10% of MK genomic DNA concentration with a wide linear calibration range of 0.05-1.5 µM (R² = 0.9891) and RSD value of 3.77% (n = 3). The results of the developed DNA biosensor provide high promise for the development of portable sensors employed in the determination of MK variety in the field.

Ultrasensitive electrochemical genosensors for species-specific diagnosis of malaria

The absence of reliable species-specific diagnostic tools for malaria at point-of-care (POC) remains a major setback towards effective disease management. This is partly due to the limited sensitivity and specificity of the current malaria POC diagnostic kits especially in cases of low-density parasitaemia and mixed species infections. In this study, we describe the first label-free DNA-based genosensors based on electrochemical impedance spectroscopy (EIS) for species-specific detection of P. falciparum, P. malariae and P. ovale. The limits of detection (LOD) for the three species-specific genosensors were down in attomolar concentrations ranging from 18.7 aM to 43.6 aM, which is below the detection limits of previously reported malaria genosensors. More importantly, the diagnostic performance of the three genosensors were compared to quantitative real-time polymerase chain reaction (qPCR) assays using purified genomic DNA and the paired whole blood lysates from clinical samples. Remarkably, all the qPCR-positive purified genomic DNA samples were correctly identified by the genosensors indicating 100% sensitivity for each of the three malaria species. The specificities of the three genosensors ranged from 66.7% to 100.0% with a Therapeutic Turnaround Time (TTAT) within 30 min, which is comparable to the TTAT of current POC diagnostic tools for malaria. This work represents a significant step towards the development of accurate and rapid species-specific nucleic acid-based toolkits for the diagnosis of malaria at the POC.

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.

Recent Developments of Carbon Dots in Biosensing: A Review

Early diagnosis of diseases is of great importance because it increases the chance of a cure and significantly reduces treatment costs. Thus, development of rapid, sensitive, and reliable biosensing techniques is essential for the benefits of human life and health. As such, various nanomaterials have been explored to improve performance of biosensors, among which, carbon dots (CDs) have received enormous attention due to their excellent performance. In this Review, the recent advancements of CD-based biosensors have been carefully summarized. First, biosensors are classified according to their sensing strategies, and the role of CDs in these sensors is elaborated in detail. Next, several typical CD-based biosensors (including CD-only, enzymatic, antigen-antibody, and nucleic acid biosensors) and their applications are fully discussed. Last, advantages, challenges, and perspectives on the future trends of CD-based biosensors are highlighted.

Highly Sensitive Fluorescence Sensor for Carrageenan from a Composite Methylcellulose/Polyacrylate Membrane

Carrageenans are linear sulphated polysaccharides that are commonly added into confectionery products but may exert a detrimental effect to human health. A new and simpler way of carrageenan determination based on an optical sensor utilizing a methylcellulose/poly(n-butyl acrylate) (Mc/PnBA) composite membrane with immobilized methylene blue (MB) was developed. The hydrophilic Mc polymer membrane was successfully modified with a more hydrophobic acrylic polymer. This was to produce an insoluble membrane at room temperature where MB reagent could be immobilized to build an optical sensor for carrageenan analysis. The fluorescence intensity of MB in the composite membrane was found to be proportional to the carrageenan concentrations in a linear manner (1.0–20.0 mg L⁻¹, R² = 0.992) and with a detection limit at 0.4 mg L⁻¹. Recovery of spiked carrageenan into commercial fruit juice products showed percentage recoveries between 90% and 102%. The optical sensor has the advantages of improved sensitivity and better selectivity to carrageenan when compared to other types of hydrocolloids. Its sensitivity was comparable to most sophisticated techniques for carageenan analysis but better than other types of optical sensors. Thus, this sensor provides a simple, rapid, and sensitive means for carageenan analysis.

Titanium dioxide-mediated resistive nanobiosensor for E. coli O157:H7

A titanium dioxide nanoparticle (TiO₂ NP)-mediated resistive biosensor is described for the determination of DNA fragments of Escherichia coli O157:H7 (E. coli O157:H7). The sol-gel method was used to synthesize the TiO₂ NP, and microlithography was applied to fabricate the interdigitated sensor electrodes. Conventional E. coli DNA detections are facing difficulties in long-preparation-and-detection-time (more than 3 days). Hence, electronic biosensor was introduced by measuring the current-voltage (I-V) DNA probe without amplification of DNA fragments. The detection scheme is based on the interaction between the electron flow on the sensor and the introduction of negative charges from DNA probe and target DNA. The biosensor has a sensitivity of 1.67 × 10¹³ Ω/M and a wide analytical range. The limit detection is down to 1 × 10^-11 M of DNA. The sensor possesses outstanding repeatability and reproducibility and is cabable to detect DNA within 15 min in a minute-volume sample (1 μL). Graphical abstract Fig. (a) Graphical illustration of electronic biosensor set up and (b) relationship between limit of detection (LOD) and the unaffected poultry samples on E. coli O157:H7.

Electrochemical biosensors based on antibody, nucleic acid and enzyme functionalized graphene for the detection of disease-related biomolecules

The application of biomacromolecule functionalized graphene electrochemical biosensors in the detection of pathogens and disease markers was reviewed.

Rapid Catalytic Reduction of 4-Nitrophenol and Clock Reaction of Methylene Blue using Copper Nanowires

Copper nanowires (CuNWs) with a high aspect ratio of ~2600 have been successfully synthesized by using a facile hydrothermal method. The reductions of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and methylene blue (MB) to leucomethylene blue (LMB) by using sodium borohydride (NaBH4) were used as models to test the catalytic activity of CuNWs. We showed that by increasing the CuNWs content, the rate of reduction increased as well. The CuNWs showed an excellent catalytic performance where 99% reduction of 4-NP to 4-AP occurred in just 60 s by using only 0.1 pg of CuNWs after treatment with glacial acetic acid (GAA). The rate constant (kapp) and activity factor (K) of this study is 18 and ~1010 fold in comparison to previous study done with no GAA treatment applied, respectively. The CuNWs showed an outstanding catalytic activity for at least ten consecutive reusability tests with a consistent result in 4-NP reduction. In clock reaction of MB, approximately 99% of reduction of MB into LMB was achieved in ~5 s by using 2 μg CuNWs. Moreover, the addition of NaOH can improve the rate and degree of recolorization of LMB to MB.

A glucose biosensor based on the immobilization of glucose oxidase and Au nanocomposites with polynorepinephrine

The PNE/GOD/AuNPs@PNE/Au electrode exhibited a low Michaelis–Menten constant, a fast response to glucose, outstanding anti-interference ability and high sensitivity.

Recent advances in graphene-based biosensor technology with applications in life sciences

Graphene's unique physical structure, as well as its chemical and electrical properties, make it ideal for use in sensor technologies. In the past years, novel sensing platforms have been proposed with pristine and modified graphene with nanoparticles and polymers. Several of these platforms were used to immobilize biomolecules, such as antibodies, DNA, and enzymes to create highly sensitive and selective biosensors. Strategies to attach these biomolecules onto the surface of graphene have been employed based on its chemical composition. These methods include covalent bonding, such as the coupling of the biomolecules via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide reactions, and physisorption. In the literature, several detection methods are employed; however, the most common is electrochemical. The main reason for researchers to use this detection approach is because this method is simple, rapid and presents good sensitivity. These biosensors can be particularly useful in life sciences and medicine since in clinical practice, biosensors with high sensitivity and specificity can significantly enhance patient care, early diagnosis of diseases and pathogen detection. In this review, we will present the research conducted with antibodies, DNA molecules and, enzymes to develop biosensors that use graphene and its derivatives as scaffolds to produce effective biosensors able to detect and identify a variety of diseases, pathogens, and biomolecules linked to diseases.