Electrochemical biosensor for the detection of a sequence of the TP53 gene using a methylene blue labelled DNA probe

A double methylene blue labeled single-stranded DNA and hairpin DNA coupling biosensor for the detection of Fusarium oxysporum f. sp. cubense race 4

The DCL gene in Fusarium oxysporum f. sp. cubense Race 4 (Foc4) is a pivotal pathogenic factor causing banana fusarium wilt. Precise DCL detection is crucial for Foc4 containment. Here, we present a novel ssDNA-hDNA coupling electrochemical biosensor for highly specific DCL detection. The sensing interface was formed via electrodeposition of a composite containing reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) onto a carbon screen-printed electrode (SPE), followed by thiol-modified ssDNA functionalization. Additionally, the incorporation of hDNA, with methylene blue (MB) at both ends, binds to ssDNA through base complementarity, forming an ssDNA-hDNA coupling probe with bismethylene blue. This sensing strategy relies on DCL recognition by the hDNA probe, leading to DNA hairpin unfolding and detachment of hDNA bearing two MBs from ssDNA, generating a robust "on-off" signal. Empirical results demonstrate the sensor's amplified electrical signals, reduced background currents, and an extended detection range (6.02 × 106-3.01 × 1010 copies/μL) with a limit of detection (3.01 × 106 copies/μL) for DCL identification. We applied this sensor to analyze soil, banana leaves, and fruit samples, confirming its high specificity and stability. Moreover, post-sample detection, the sensor exhibits reusability, offering a cost-effective and rapid approach for banana wilt detection.

Advances in Bioelectrode Design for Developing Electrochemical Biosensors

The critical performance factors such as selectivity, sensitivity, operational and storage stability, and response time of electrochemical biosensors are governed mainly by the function of their key component, the bioelectrode. Suitable design and fabrication strategies of the bioelectrode interface are essential for realizing the requisite performance of the biosensors for their practical utility. A multifaceted attempt to achieve this goal is visible from the vast literature exploring effective strategies for preparing, immobilizing, and stabilizing biorecognition elements on the electrode surface and efficient transduction of biochemical signals into electrical ones (i.e., current, voltage, and impedance) through the bioelectrode interface with the aid of advanced materials and techniques. The commercial success of biosensors in modern society is also increasingly influenced by their size (and hence portability), multiplexing capability, and coupling in the interface of the wireless communication technology, which facilitates quick data transfer and linked decision-making processes in real-time in different areas such as healthcare, agriculture, food, and environmental applications. Therefore, fabrication of the bioelectrode involves careful selection and control of several parameters, including biorecognition elements, electrode materials, shape and size of the electrode, detection principles, and various fabrication strategies, including microscale and printing technologies. This review discusses recent trends in bioelectrode designs and fabrications for developing electrochemical biosensors. The discussions have been delineated into the types of biorecognition elements and their immobilization strategies, signal transduction approaches, commonly used advanced materials for electrode fabrication and techniques for fabricating the bioelectrodes, and device integration with modern electronic communication technology for developing electrochemical biosensors of commercial interest.

Designing of a unique bioreceptor and fabrication of an efficient genosensing platform for neonatal sepsis detection

We report the results of studies related to the fabrication of a nanostructured graphene oxide (GO)-based electrochemical genosensor for neonatal sepsis detection. Initially, we selected the fimA gene of E. coli for nenonatal sepsis detection and further designed a 20-mer long amine-terminated oligonucleotide. This designed oligonucleotide will work as a bioreceptor for the detection of the virulent fimA gene. An electrochemical genosensor was further developed where GO was used as an immobilization matrix. For the formation of a thin film of GO on an indium tin oxide (ITO)-coated glass electrode, an optimized DC potential of 10 V for 90 s was applied via an electrophoretic deposition unit. Thereafter, the designed oligonucleotides were immobilized through EDC-NHS chemistry. The nanomaterial and fabricated electrodes were characterized via X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and cyclic voltammetry techniques. The fabricated genosensor (BSA/pDNA/GO/ITO) has the ability to detect the target fimA gene with a linear detection range of 10-12 M to 10-6 M, a lower detection limit of 10-12 M and a sensitivity of 114.7 μA M-1 cm-2. We also investigated the biosensing ability of the developed genosensor in an artificial serum sample and the obtained electrochemical results were within the acceptable percentage relative standard deviation (% RSD), indicating that the fabricated genosensor can be used for the detection of neonatal sepsis by using a serum sample.

Design of a rapid electrochemical biosensor based on MXene/Pt/C nanocomposite and DNA/RNA hybridization for the detection of COVID-19

Since the rapid spread of the SARS-CoV-2 (2019), the need for early diagnostic techniques to control this pandemic has been highlighted. Diagnostic methods based on virus replication, such as RT-PCR, are exceedingly time-consuming and expensive. As a result, a rapid and accurate electrochemical test which is both available and cost-effective was designed in this study. MXene nanosheets (Ti₃C₂Tx) and carbon platinum (Pt/C) were employed to amplify the signal of this biosensor upon hybridization reaction of the DNA probe and the virus's specific oligonucleotide target in the RdRp gene region. By the differential pulse voltammetry (DPV) technique, the calibration curve was obtained for the target with varying concentrations ranging from 1 aM to 100 nM. Due to the increase in the concentration of the oligonucleotide target, the signal of DPV increased with a positive slope and a correlation coefficient of 0.9977. Therefore, at least a limit of detection (LOD) was obtained 0.4 aM. Furthermore, the specificity and sensitivity of the sensors were evaluated with 192 clinical samples with positive and negative RT-PCR tests, which revealed 100% accuracy and sensitivity, 97.87% specificity and limit of quantification (LOQ) of 60 copies/mL. Besides, various matrices such as saliva, nasopharyngeal swabs, and serum were assessed for detecting SARS-CoV-2 infection by the developed biosensor, indicating that this biosensor has the potential to be used for rapid Covid-19 test detection.

Electrochemical sensor based on Fe3O4/α-Fe2O3@Au magnetic nanocomposites for sensitive determination of the TP53 gene

Considering the high cost and tedious process of gene sequencing, there is an urgent need to develop portable and efficient sensors for the TP53 gene. Here, we developed a novel electrochemical sensor that detected the TP53 gene using magnetic peptide nucleic acid (PNA)-modified Fe₃O₄/α-Fe₂O₃@Au nanocomposites. Cyclic voltammetry and electrochemical impedance spectroscopy confirmed the successful stepwise construction of the sensor, especially the high-affinity binding of PNA to DNA strands, which induced different electron transfer rates and resulted in current changes. Variations in the differential pulse voltammetry current observed during hybridization at different surface PNA probe densities, hybridization times, and hybridization temperatures were explored. The biosensing strategy obtained a limit of detection of 0.26 pM, a limit of quantification of 0.85 pM, and a wide linear range (1 pM-1 μM), confirming that the Fe₃O₄/α-Fe₂O₃@Au nanocomposites and the strategy based on magnetic separation and magnetically induced self-assembly improved the binding efficiency of nucleic acid molecules. The biosensor was a label-free and enzyme-free device with excellent reproducibility and stability that could identify single-base mismatched DNA without additional DNA amplification procedures, and the serum spiked experiments revealed the feasibility of the detection approach.

Sensitive Electrochemical Biosensor for Rapid Screening of Tumor Biomarker TP53 Gene Mutation Hotspot

Rapid and sensitive detection of cancer biomarkers is crucial for cancer screening, early detection, and improving patient survival rate. The present study proposes an electrochemical gene-sensor capable of detecting tumor related TP53 gene mutation hotspots by self-assembly of sulfhydryl ended hairpin DNA probes tagged with methylene blue (MB) onto a gold electrode. By performing a hybridization reaction with the target DNA sequence, the gene-sensor can rearrange the probe’s structure, resulting in significant electrochemical signal differences by differential pulse voltammetry. When the DNA biosensor is hybridized with 1 μM target DNA, the peak current response signal can decrease more than 60%, displaying high sensitivity and specificity for the TP53 gene. The biosensor achieved rapid and sensitive detection of the TP53 gene with a detection limit of 10 nmol L⁻¹, and showed good specific recognition ability for single nucleotide polymorphism (SNP) and base sequence mismatches in the TP53 gene affecting residue 248 of the P53 protein. Moreover, the biosensor demonstrated good reproducibility, repeatability, operational stability, and anti-interference ability for target DNA molecule in the complex system of 50% fetal bovine serum. The proposed biosensor provides a powerful tool for the sensitive and specific detection of TP53 gene mutation hotspot sequences and could be used in clinical samples for early diagnosis and detection of cancer.