Search Results (145)

We developed a sensor consisting of V₂O₅ nanorods and a reduced graphene oxide (rGO) nanocomposite (V₂O₅/rGO) with immobilized DNA aptamers (Apt-NH@V₂O₅/rGO) for the sensitive electrochemical detection of Hg (II). The V₂O₅ nanorods anchored on rGO nanosheets were synthesized using a hydrothermal method. The nanocomposite was analyzed by various powerful physical methods that include X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, the Brunauer–Emmett–Teller (BET) method, and Fourier transform infrared spectroscopy (FTIR). The FE-SEM of V₂O₅ disclosed the nanorod-like structure and uniform anchoring of V₂O₅ on the rGO nanosheet. Moreover, the BET results showed that the V₂O₅/rGO nanocomposite possesses excellent porosity. Furthermore, a glassy carbon electrode (GCE) was modified with Apt-NH@V₂O₅/rGO and used for the electrochemical detection of Hg(II) by differential pulse voltammetry (DPV). The aptasensor exhibited excellent sensitivity and selectivity toward Hg(II) detection, with a limit of detection (LOD) of 5.57 nM, which is below the maximum permissible limit established by WHO for rivers (30 nM). The sensor also exhibited significant stability and good repeatability. Full article

Infectious bronchitis virus (IBV) is an enveloped, positive-sense, single-stranded RNA virus belonging to the genus Gammacoronavirus. It primarily infects avian species, causing respiratory and renal disease and irreversible damage to the oviduct, which can lead to high mortality rates in chickens. The lack of rapid and reliable diagnostic tools for on-farm IBV detection hampers timely disease management and control measures. The introduction of DNA biosensors offers a promising approach for the sensitive and specific detection of IBV, facilitating rapid identification and intervention. In this study, an electrochemical DNA biosensor with a multi-walled carbon nanotube (MWCNT)-modified gold electrode was developed for IBV detection. The biosensor targeted the target-specific 5′ untranslated region (5′-UTR) of the IBV genome. Under optimal conditions, the immobilization and hybridization efficiencies were evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), with methylene blue as a redox indicator. The developed DNA biosensor demonstrated a dynamic detection range from 2.0 × 10⁻¹² to 2.0 × 10⁻⁵ mol L⁻¹, with a limit of detection (LOD) of 2.6 nM and a limit of quantification (LOQ) of 0.79 nM. Validation using a small subset of clinical samples, including crude complementary DNA, and polymerase chain reaction products, showed high recovery rates ranging from 95.41% to 99.55%. While these findings highlight the potential of the proposed DNA biosensor as an innovative diagnostic tool for IBV detection, this study remains a proof of concept. However, further validation using a large number of clinical samples is essential to assess its feasibility, robustness, and practical application in a real-world farm setting Full article

In this study, we developed a label-free biosensor based on aptamer-modified multi-walled carbon nanotube extended gate field-effect transistor (MWCNT-EG-FET) for easy and selective detection of microcystin-LR (MC-LR), a prominent cyanotoxin associated with liver damage, bleeding, and necrosis. EG-FET had two parts: a MOSFET and an extended-gate Au/SiO₂ electrode, which serves as the sensitive membrane. A custom-designed DNA oligonucleotide (5-NH₂-C₆-AN6) was used as MC-LR-targeting aptamer (MCTA). MWCNTs were functionalized with MCTA and then stably fixed on the sensitive membrane. The detection of MC-LR in freshwater was effectively achieved within 5 min by assessing the variations in electrical resistance that occur due to the selective interactions between MC-LR and MCTA. The detection limit and analytical sensitivity of the biosensor for MC-LR were found to be 0.134 ng/mL and 0.024 ng/mL, respectively. The sensitive membrane could be readily discarded if damaged, eliminating the need to replace the main transducer MOSFET. The developed sensor exhibits features such as straightforward preparation, swift response, potential for miniaturization, and ease of use, making it an attractive candidate for future integrated lab-on-chip systems for MC-LR detection in freshwater environments. Full article

The development of electrochemical DNA biosensors occurred by applying different organically coated Mn-NPs such as MnCO₃@OAm, MnCO₃@TEG and MnO₂/Mn₂O₃@TEG, as well as naked MnCO₃ NPs (where OAm = oleylamine and TEG = tetraethylene glycol). The detection performances of PGEs were modified with different types of Mn-NPs, according to the guanine signal magnitudes obtained after double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) immobilization at these surfaces. DNA interaction studies were realized using UV-vis, circular dichroism (CD), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) techniques. In addition, a 3- to 5.4-fold increase in guanine response in the presence of dsDNA and a 2.3-fold increase in the presence of ssDNA were obtained with the developed biosensor. The increased signals in DNA immobilization at the electrode surfaces modified with Mn-NPs compared to bare PGE clearly show that the modification of Mn-NPs increases the electroactive surface area of the electrode. The detection limit (LOD) of dsDNA was calculated as 7.86 μg·L⁻¹ using the MnO₂/Mn₂O₃@TEG type of the Mn-NP-modified biosensor, while the detection limit of ssDNA was calculated as 3.49 μg·L⁻¹ with the MnCO₃@OAm type Mn-NP-modified biosensor. The proposed sensor was applied to a human DNA sample where the amount of dsDNA extract was found to be 0.62 ± 0.03 mg·L⁻¹ after applying the MnO₂/Mn₂O₃@TEG type of Mn-NP-modified biosensor. Full article

Food safety is a pressing global concern due to the risks posed by contaminants such as pesticide residues, heavy metals, allergens, mycotoxins, and pathogenic microorganisms. While accurate, traditional detection methods like ELISA, HPLC, and mass spectrometry are often time-consuming and resource-intensive, highlighting the need for innovative alternatives. Biosensors based on biological recognition elements such as enzymes, antibodies, and aptamers, offer fast, sensitive, and cost-effective solutions. Using transduction mechanisms like electrochemical, optical, piezoelectric, and thermal systems, biosensors provide versatile tools for detecting contaminants. Advances in DNAzyme- and aptamer-based technologies enable the precise detection of heavy metals, while enzyme- and protein-based biosensors monitor metal-induced changes in biological activity. Innovations like microbial biosensors and DNA-modified electrodes enhance detection accuracy. Biosensors are also highly effective in identifying pesticide residues, allergens, mycotoxins, and pathogens through immunological, enzymatic, and nucleic acid-based techniques. The integration of nanomaterials and bioelectronics has significantly improved the sensitivity and performance of biosensors. By facilitating real-time, on-site monitoring, these devices address the limitations of conventional methods to ensure food quality and regulatory compliance. This review highlights the transformative role of biosensors and how biosensors are improved by emerging technologies in food contamination detection, emphasizing their potential to mitigate public health risks and enhance food safety throughout the supply chain. Full article

Rapid, effective, and cost-effective methods for large-scale screening of pesticide residues in the environment and agricultural products are important for assessing potential environmental risks and safeguarding human health. Here, we constructed a novel aggregation-induced emission (AIE) electrochemical aptamer (Apt) sensor based on red-emissive sulfur quantum dots (SQDs), which aimed at the rapid screening and quantitative detection of malathion. SQDs were prepared using a two-step oxidation method with good electrochemiluminescence (ECL) optical properties. These SQDs were modified onto the electrode surface to serve as ECL luminophores. Subsequently, Apt was introduced and modified to form a double-helix structure with the complementary chain (cDNA). The ECL signal was reduced because the biomolecules had poor electrical conductivity and inefficient electron transfer. When the target malathion was added, the double helix structure was unraveled, the malathion Apt fell off the electrode surface, and the ECL signal was restored. The linear range of detection was 1.0 × 10⁻¹³–1.0 × 10⁻⁸ mol·L⁻¹, and the detection limit was 0.219 fM. The successful preparation of the sensor not only develops the ECL optical properties of SQDs but also expands the application of SQDs in ECL sensing. Full article

In the biosensor field, the accurate detection of contagious disease has become one of the most important research topics in the post-pandemic period. However, conventional contagious viral biosensors normally require chemical modifications to introduce the probe molecules to nucleic acids such as a redox indicator, fluorescent dye, or quencher for biosensing. To avoid this complex chemical modification, in this research, mismatched DNA with an intercalated metal ion complex (MIMIC) is employed as the probe sequence. In addition, the MIMIC is fabricated on a lithography-assisted nanostructure-modified flexible polymer electrode. On this flexible electrode, as a proof-of-concept study, a human papillomavirus (HPV-16 and -18) was detected by the MIMIC with a high accuracy. The developed biosensor exhibits an ultrasensitive ability to detect HPV in viral DNA without target amplification and chemical modifications in a simple preparation manner. Moreover, it retains its nanostructures and high conductivity after bending. In conclusion, the use of the proposed biosensor suggests a novel approach to developing an ultrasensitive and flexible biosensor for the detection of important biomarkers in a simple manner that can be applied in point-of-care testing. Full article

Objectives: The main aim of our experiments was to demonstrate the suitability of cell-based biosensors for searching for new anticancer medicinal preparations. Methods: The effect of the substance doxorubicin, doxorubicin embedded in phospholipid nanoparticles, and doxorubicin with phospholipid nanoparticles modified by targeting vectors (cRGD and folic acid) on dsDNA and breast cancer cell lines (MCF-7, MDA-MB-231) was studied. Results: In the obtained doxorubicin nanoforms, the particle size was less than 60 nm. Our study of the percentage of doxorubicin inclusion showed the almost complete embeddability of the substance into nanoparticles for all samples, with an average of 95.4 ± 4.6%. The calculation of the toxicity index of the studied doxorubicin samples showed that all substances were moderately toxic drugs in terms of adenine and guanine. The biosensor analysis using electrodes modified with carbon nanotubes showed an intercalation interaction between doxorubicin and its derivatives and dsDNA, except for the composition of doxorubicin with folic acid with a linker length of 2000 (NPh-Dox-Fol(2.0)). The results of the electroanalysis were normalized to the total cell protein (mg) and cell concentration. The highest intensity of the electrochemical signals was observed in intact control cells of the MCF-7 and MDA-MB-231 cell lines. Conclusions: The proposed electrochemical approach is useful for the analysis of cell line responses to the medicinal preparations. Full article

This review explores electrochemical sensing strategies for synthetic orange dyes, addressing the growing need for sensitive and selective detection methods in various industries. We examine the fundamental principles underlying the electrochemical detection of these compounds, focusing on their redox behavior and interaction with electrode surfaces. The review covers a range of sensor designs, from unmodified electrodes to advanced nanomaterial-based platforms. Chemically modified electrodes incorporating polymers and molecularly imprinted polymers are discussed for their enhanced selectivity. Particular attention is given to nanomaterial-based sensors, including those utilizing carbon nanotubes, graphene derivatives, and metal nanoparticles, which have demonstrated exceptional sensitivity and wide linear ranges. The potential of biological-based approaches, such as DNA interaction sensors and immunosensors, is also evaluated. Current challenges in the field are addressed, including matrix effects in complex samples and long-term stability issues. Emerging trends are highlighted, including the development of multi-modal sensing platforms and the integration of artificial intelligence for data analysis. The review concludes by discussing the commercial potential of these sensors in food safety, environmental monitoring, and smart packaging applications, emphasizing their importance in ensuring the safe use of synthetic orange dyes across industries. Full article

A novel sandwich-type electrochemical aptasensor based on supramolecularly immobilized affinity bioreceptor was prepared via host–guest interactions. This method utilizes an adamantane-modified, target-responsive hairpin DNA aptamer as a capture molecular receptor, along with a perthiolated β-cyclodextrin (CD) covalently attached to a gold-modified electrode surface as the transduction element. The proposed sensing strategy employed an enzyme-modified aptamer as the signalling element to develop a sandwich-type aptasensor for detecting prostate-specific antigen (PSA). To achieve this, screen-printed carbon electrodes (SPCEs) with electrodeposited reduced graphene oxide (RGO) and gold nanoferns (AuNFs) were modified with the CD derivative to subsequently anchor the adamantane-modified anti-PSA aptamer via supramolecular associations. The sensing mechanism involves the affinity recognition of PSA molecules on the aptamer-enriched electrode surface, followed by the binding of an anti-PSA aptamer–horseradish peroxidase complex as a labelling element. This sandwich-type arrangement produces an analytical signal upon the addition of H₂O₂ and hydroquinone as enzyme substrates. The aptasensor successfully detected the biomarker within a concentration range of 0.5 ng/mL to 50 ng/mL, exhibiting high selectivity and a detection limit of 0.11 ng/mL in PBS. Full article

Direct detection of miRNA is currently limited by the complex amplification and reverse transcription processes of existing methods, leading to low sensitivity and high operational demands. Herein, we developed a CRISPR/Cas13a-mediated photoelectrochemical (PEC) biosensing platform for direct and sensitive detection of miRNA-21. The direct and specific recognition of target miRNA-21 by crRNA-21 eliminates the need for pre-amplification and reverse transcription of miRNA-21, thereby preventing signal distortion and enhancing the sensitivity and precision of target detection. When crRNA-21 binds to miRNA-21, it activates the trans-cleavage activity of CRISPR/Cas13a, leading to the non-specific cleavage of biotin-modified DNA with uracil bases (biotin-rU-DNA). This cleavage prevents the biotin-rU-DNA from being immobilized on the electrode surface. As a result, streptavidin cannot attach to the electrode via specific biotin binding, reducing spatial resistance and causing a positively correlated increase in the photocurrent response. This Cas-PEC biosensor has good analytical capabilities, linear responses between 10 fM and 10 nM, a minimum detection limit of 9 fM, and an excellent recovery rate in the analysis of real human serum samples. This work presented an innovative solution for detecting other biomarkers in bioanalysis and clinical diagnostics. Full article

Graphene, known for its outstanding physical and chemical properties, is widely used in various fields, including electronics and biomedicine. Reduced graphene oxide (rGO) is preferred for electrochemical applications due to its enhanced water solubility and dispersion. Electrochemically reduced graphene oxide (ErGO) is particularly advantageous as it can be prepared under mild conditions and simplifies sensor fabrication; however, ErGO-based electrochemical sensors often lack specificity. Bioreceptors like proteins, enzymes, and DNA/RNA aptamers are incorporated to provide high specificity. This study introduces a guanine (G)/cytosine (C)-modified ErGO electrode (G/C@ErGO-GCE) for the sensitive electrochemical detection of doxorubicin (DOX) with good selectivity. The G/C mixture acts as a bioreceptor and is anchored on the ErGO-GCE surface via π-π interactions. The G/C@ErGO-GCE was characterized using scanning electron microscopy, contact angle measurement, Raman spectroscopy, and electrochemical methods. The sensor demonstrated excellent dynamic range (DPV: 10 nM to 1 µM, CA: 30 nM to 1.3 µM), sensitivity (DPV: 2.17 µA/µM, CA: 6.79 µA/µM), limit of detection (DPV: 84 nM, CA: 34 nM), and selectivity for DOX detection, highlighting its potential for biomedical applications and pharmacokinetic studies. Full article

Heavy metals constitute pollutants that are particularly common in air, water, and soil. They are present in both urban and rural environments, on land, and in marine ecosystems, where they cause serious environmental problems since they do not degrade easily, remain almost unchanged for long periods, and bioaccumulate. The detection and especially the quantification of metals require a systematic process. Regular monitoring is necessary because of seasonal variations in metal levels. Consequently, there is a significant need for rapid and low-cost metal determination methods. In this study, we compare and analytically validate absorption spectrometry with a sensitive voltammetric method, which uses a bismuth film-plated electrode surface and applies stripping voltammetry. Atomic absorption spectroscopy (AAS) represents a well-established analytical technique, while the applicability of anodic stripping voltammetry (ASV) in complicated sample matrices such as soil samples is currently unknown. This sample-handling challenge is investigated in the present study. The results show that the AAS and ASV methods were satisfactorily correlated and showed that the metal concentration in soils was lower than the limit values but with an increasing trend. Therefore, continuous monitoring of metal levels in the urban complex of a city is necessary and a matter of great importance. The limits of detection of cadmium (Cd) were lower when using the stripping voltammetry (SWASV) graphite furnace technique compared with those obtained with AAS when using the graphite furnace. However, when using flame atomic absorption spectroscopy (flame-AAS), the measurements tended to overestimate the concentration of Cd compared with the values found using SWASV. This highlights the differences in sensitivity and accuracy between these analytical methods for detecting Cd. The SWASV method has the advantage of being cheaper and faster, enabling the simultaneous determination of heavy elements across the range of concentrations that these elements can occur in Mediterranean soils. Additionally, a dsDNA biosensor is suggested for the discrimination of Cu(I) along with Cu(II) based on the oxidation peak of guanine, and adenine residues can be applied in the redox speciation analysis of copper in soil, which represents an issue of great importance. Full article

Massive use of antibiotics in veterinary medicine has led to their accumulation in meat and dairy products. Consumption of antibiotic-contaminated food can trigger the development of antibiotic-resistant bacteria, endangering human lives. Among antibiotics, the oxytetracycline (OTC) family of antibiotics is most widely used in veterinary medicine. Strict control of the antibiotics in food necessitates the development of fast and effective methods for OTC detection, for instance, in milk. One of the most promising approaches to OTC detection is based on the use of specially designed DNA aptamers. These DNA aptamers are relatively short, 15–60 bases, nucleotides folded in the solution in a 3D structure, forming a binding site for the target antibiotic. Aptamers can be chemically modified for attachment to sensor electrodes. In this work, we investigated the electrochemical detection of OTC using DNA aptamers specific to OTC that have been covalently immobilized onto the nanocomposite surface of a glassy carbon electrode with electrodeposited reduced graphene oxide and multiwalled carbon nanotubes. Differential pulse voltammetry, DPV, in the presentence of a ferri/ferrocyanide redox couple was used as an internal standard and to monitor the redox current. In the presence of OTC, the amplitude of DPV decreased, evidencing the blocking of charge transfer. After system optimization, we reached the limit of detection of 0.45 ng OTC/mL, which is 200 times lower than the maximum residue limit established by the European Commission of 100 ng OTC/mg. Full article

In this work, we conducted a study of the interaction between DNA and favipiravir (FAV). This chemotherapeutic compound is an antiviral drug for the treatment of COVID-19 and other infections caused by RNA viruses. This paper examines the electroanalytical characteristics of FAV. The determined concentrations correspond to therapeutically significant ones in the range of 50–500 µM (R² = 0.943). We have shown that FAV can be electro-oxidized around the potential of +0.96 V ÷ +0.98 V (vs. Ag/AgCl). A mechanism for electrochemical oxidation of FAV was proposed. The effect of the drug on DNA was recorded as changes in the intensity of electrochemical oxidation of heterocyclic nucleobases (guanine, adenine and thymine) using screen-printed graphite electrodes modified with single-walled carbon nanotubes and titanium oxide nanoparticles. In this work, the binding constants (Kb) of FAV/dsDNA complexes for guanine, adenine and thymine were calculated. The values of the DNA-mediated electrochemical decline coefficient were calculated as the ratio of the intensity of signals for the electrochemical oxidation of guanine, adenine and thymine in the presence of FAV to the intensity of signals for the electro-oxidation of these bases without drug (S, %). Based on the analysis of electrochemical parameters, values of binding constants and spectral data, intercalation was proposed as the principal mechanism of the antiviral drug FAV interaction with DNA. The interaction with calf thymus DNA also confirmed the intercalation mechanism. However, an additional mode of interaction, such as a damage effect together with electrostatic interactions, was revealed in a prolonged exposure of DNA to FAV. Full article