Electrochemical biosensors for bioprocess control.
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Biosensing Techniques↗
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Electrochemical Duplex Detection of E2 and E6 Genes of Human Papillomavirus Type 16 and Determination of Physical Status in High-Risk Cervical Carcinoma.
Human papillomavirus type 16 (HPV-16) is a key driver in the development of cervical carcinoma, with the integration of its genome into the host DNA marking a critical step in disease progression. Monitoring the physical state of HPV-16, particularly the transition from episomal to integrated forms, is essential for evaluating the risk of malignancy development in cervix. This study presents the development of a duplex electrochemical biosensor for the simultaneous detection of the E2 and E6 genes of HPV-16. Using a one-step sandwich hybridization assay, the biosensor was able to detect HPV-16 E2 and E6 genes with a sensitivity of 8 copies/mL and 12 copies/mL respectively and distinguish between the episomal and integrated forms based on the E2/E6 ratio (cut-off 0.77, 100% sensitivity/specificity). The sensor was validated with 30 clinical cervical tissue samples, providing results comparable to qPCR method. This novel biosensor offers a rapid and efficient platform for the detection and monitoring of HPV-16, with potential applications in cervical cancer screening and prognosis.
Humans↗
From host response to genomic targets: electrochemical biosensing of tuberculosis biomarkers.
Tuberculosis (TB) remains one of the leading causes of death from a single infectious agent worldwide, with timely diagnosis continuing to be a major challenge, particularly in resource-limited settings. Conventional TB diagnostic methods are limited by low sensitivity, long turnaround times, and an inability to reliably differentiate latent from active disease. Biomarker-based diagnostic strategies have therefore gained increasing attention as they offer the potential to improve early detection, disease differentiation, and treatment monitoring. Herein, we examine electrochemical biosensing strategies for TB diagnostics using a biomarker-class-driven framework, covering host-response biomarkers (IFN-γ and TNF-α), pathogen-derived antigens (ESAT6, CFP10, CFP10-ESAT6, MPT64, Ag85, HspX and LpqH), cell-wall signatures and whole-cell markers (LAM and whole cell Mtb), and genomic markers (Mtb DNA and IS6110). Through structured comparison of recognition elements, biointerface designs, signal amplification strategies, electrochemical techniques, matrices, and validation levels, this review identifies the most promising technical approaches for different TB biomarker classes. It further highlights key translational bottlenecks, including limited clinical validation, buffer-based testing, complex multistep amplification, redox-probe dependence, matrix fouling, and insufficient evidence of manufacturability. This review therefore provides practical guidance for developing electrochemical TB biosensors that are analytically sensitive, clinically relevant, and suitable for decentralized diagnostic applications.
Biosensing Techniques↗
Spatially confined electrochemical strategy with DNA-assembled nanogaps for SNP detection.
Accurate detection of low-abundance single nucleotide polymorphisms (SNPs) against a large excess of homologous wild-type sequences requires both selective molecular recognition and effective transduction of small sequence differences into measurable signals. Here, we report a spatially confined electrochemical strategy that couples sequence-selective recognition with size-dependent mass-transport gating. DNA-hybridization-driven self-assembly of gold nanoparticles (AuNPs) forms a three-dimensional self-assembled electrode (3D-SAE) with a DNA-defined interparticle architecture. Competitive probes (SP/WP) convert single-base recognition into distinct molecular-size states: the SNP-associated pathway preferentially triggers a hybridization chain reaction (HCR), generating bulky AuNP-anchored HCR/methylene blue complexes (Au@HCR/MB) with reduced electrochemical accessibility through the porous 3D-SAE, whereas the wild-type pathway does not trigger HCR and maintains a high-current response from more readily accessible MB-containing species. Thus, sequence recognition is translated into a molecular-size difference and subsequently into an electrochemical signal through differential mass transport. Under buffer conditions, the platform achieved a statistically estimated detection limit of ∼0.47 fM and a quantitative range of 1 fM-100 pM. It discriminated a 0.1% mutant abundance in a fragmented genomic-DNA background. The downstream signal-transduction chemistry is enzyme-free and isothermal. This work establishes a mechanistical recognition-size-conversion-mass-transport-gating architecture for electrochemical nucleic acid analysis.
Polymorphism, Single Nucleotide↗
[Biosensors and clinical analysis].
Method for the selective determination of organic compounds in biological fluids, such as blood, are very important in clinical analyses. Most analyses of organic compounds can be performed by spectrophotometric methods based on specific enzyme-catalyzed reactions. However, on account of the complicated procedure, these methods cannot be applied directly to bed-side monitoring. Alternatively, biosensors based on enzymes and electrochemical transducers possess excellent sensitivity for biological substrates and can determine directly a single compound in a biological fluid without need for a prior separation step. Therefore, in several years, many kinds of biosensors have been developed, and implantable microbiosensors for a body organ have also been reported. In the near future, an artificial pancreas fabricated by micromachine technology will be developed.
Biosensing Techniques↗
[Development and application of biosensors for medical field].
Methods for the selective determination of organic compounds in biological fluids, such as blood, are very important in clinical analyses. Most analyses of organic compounds can be performed by spectrophotometric methods, based on specific enzyme-catalyzed reactions. However, because of the complicated procedure, these methods cannot be applied directly to bed-side monitoring. Alternatively, biosensors based on enzymes and electrochemical transducers possess excellent sensitivity for biological substrates and can determine a single compound in a biological fluid directly without need for a prior separation step. Therefore, in the past several years, many kinds of biosensors have been developed, and implantable microbiosensors for a body organ have also been reported.
Biomedical Engineering↗
[Stationary kinetics of the function of multienzyme membrane sensors with electrochemical enzyme regeneration].
A theoretical analysis of the functioning of membrane biosensors based on consecutive polyenzymatic transformations of the substrate and detectable by indicator electrodes with electrochemical regeneration of the enzyme active sites, has been carried out. Correlations between the substrate concentration, diffusion-catalytic characteristics of the coating components, and rate of the indicator reaction on the one hand, and the level of the steady-state response of the polyenzymatic biosensors, on the other, have been determined for relatively low values of the polyenzymatic layer thickness. Various regimens of functioning of bienzymatic electrodes have been considered.
Binding Sites↗
Electrochemical enzyme immunoassay for detection of toxic substances.
Sensors that provide reliable, rapid measurement of toxic substances are needed to solve significant human health and safety problems. We developed a new biosensor design that combines the advantages of immunoassay with electrochemical response. We established that this enzyme-linked immunosensor measures toxic substances in biological samples. The biosensor consists of two major elements: (1) an electrical conducting layer having immobilized enzyme, polyclonal or monoclonal antibodies, and other necessary reagents, and (2) the electronic components used in the signal readout. The result is an amperometric immunoassay based on coupling the immunochemical reaction to the enzyme electrode response by using a soluble, electrochemically active mediator. The specific question addressed was: Does the system's immunochemical detection reliably respond at sufficiently low analyte concentrations? We present our results in these areas: (1) enzyme immobilization on colloidal gold; (2) colloidal gold-enzyme deposition on the electrode surface; (3) mediator-antigen conjugate synthesis; (4) antibody incorporation at the electrode surface; (5) bioelectrode characterization and optimization; and (6) immunosensor demonstration to detect antigen. Sensors that employ immunochemical detection will have broad applicability to detect/diagnose toxic substances in biological samples such as blood and urine and in environmental samples such as wastewater and drinking water.
Biosensing Techniques↗
In vivo selective monitoring of basal levels of cerebral dopamine using voltammetry with Nafion modified (NA-CRO) carbon fibre micro-electrodes.
The electrochemical technique of differential pulse voltammetry (DPV) with micro-biosensors has been used for a number of years to monitor in vivo and in situ changes in the extracellular concentration of cerebral ascorbic acid, as well as that of the metabolites of dopamine (DA) and serotonin (5-HT). We have recently prepared a carbon fibre micro-electrode (mCFE) which specifically pretreated and coated with Nafion (a negatively charged polymer which repels acids such as 3,4-dihydroxyphenylacetic acid (DOPAC)) allows the direct selective detection of the oxidation of DA and 5-HT in nanomolar concentration in vitro and that of extracellular basal levels of cerebral 5-HT in vivo (peak B at +240 mV). We describe here a modified version of this micro-biosensor now called NA-CRO mCFE as its active tip (30 microns in diameter) is coated with a 50/50 (v:v) mixture of Nafion and dibenzo-18-crown-6 (Aldrich). In vitro this newly reported electrode shows insensitivity to acids (e.g., DOPAC) up to 100 microns and sensitivity to 0.5-1 nM DA. In vivo, in the striatum of anaesthetised rats, a basal oxidation peak at +80 mV (peak A, on average 0.6 nA in height), which corresponds to the oxidation potential of DA in vitro, is consistently detectable with the NA-CRO mCFE (corresponding to an estimated concentration of 1.5 nM). Experiments performed in vivo in anaesthetised rats implanted in the striatum with uncoated (normal) mCFE to measure extracellular DOPAC or with NA-CRO mCFE have been performed in order to analyse the chemical nature of peak A in vivo. It is concluded that the addition of the crown-ether compound to the Nafion coat improves the sensitivity of the micro-biosensor for DA in vitro and allows the detection of its basal extracellular levels in vivo.
3,4-Dihydroxyphenylacetic Acid↗
Polymer membranes in clinical sensor applications. II. The design and fabrication of permselective hydrogels for electrochemical devices.
Hydrogels, particularly the tough, low water content materials, have potential advantages in the field of clinical biosensors because of their established use as medical polymers. The factors that control transport behaviour in these polymers are discussed with particular reference to ion selectivity. The nature of the transport behaviour in relation to coated wire electrode performance is presented and an extension of these permselectivity studies to the fabrication of miniaturized devices, such as ISFETs, is described. Linear soluble hydrogel polymers, coated on to sensor substrates, may be converted to insoluble membranes using solid photosensitive aromatic monomers, such as N-vinyl carbazole. Photolithographic patterning is achieved using a UV source together with appropriate masking, followed by an oxygen plasma etch process. Gas plasma etching, which selectively removes uncross-linked (masked) areas forms the basis of an all dry, low-temperature patterning process capable of giving micrometre-scale resolution. This novel photographic process, which does not damage or extract enzymes or ionophores, can advantageously be extended to the fabrication of poly(vinylchloride)-based membranes.
Biocompatible Materials↗
Artificial neural network data fusion-mediated dual-mode sensor based on Fe3O4@PdIr for Salmonellatyphimurium detection in food.
Salmonella Typhimurium (S. typhimurium) is a major foodborne pathogen that poses a serious threat to public health. In this study, a colorimetric/electrochemical dual-mode biosensor assisted by artificial neural network (ANN) was developed for the sensitive detection of S. typhimurium. Fe3O4@PdIr nanocomposites with enhanced peroxidase-like activity and electrochemical performance were prepared and conjugated with an aptamer specific to S. typhimurium to obtain Fe3O4@PdIr-Apt. Through the sandwich binding of Fe3O4@PdIr-Apt and Apt to the target, the nanocomposites were attached to microplates or Au electrodes, thereby generating colorimetric and electrochemical signals. The ANN model deeply resolved the complex nonlinear relationship between the dual signals, enabling mutual correction and ultimately performing data fusion to output a single detection result, which significantly reduced the mean square error while improving detection sensitivity and reliability. This sensor exhibited a wide linear range of 2.7-2.7 × 108 CFU/mL and a low detection limit of 1.66 CFU/mL. Additionally, this method was successfully applied to the detection of S. typhimurium in pork and milk, with a recovery rate of 95.19% ∼ 104.07%. It indicated that the constructed sensor holds great practical potential for S. typhimurium detection.
Neural Networks, Computer↗
Sensitive detection of pesticides using amperometric sensors based on cobalt phthalocyanine-modified composite electrodes and immobilized cholinesterases.
The determination of organophosphate and carbamate pesticides was carried out using cobalt phthalocyanine-modified carbon epoxy composite electrodes coupled with acetylcholinesterase or butyrylcholinesterase. Covalent immobilization of enzymes on Immobilon membranes or nylon nets was examined; the highest sensitivity to inhibitors was found for the nylon net containing low enzyme loading and this was subsequently used for the construction of an amperometric biosensor for pesticides. Analyses were done using acetyl- or butyrylthiocholine as substrates; thiocholine produced by hydrolysis in the enzyme membrane was electrochemically oxidized at +300 mV (vs. Ag/AgCl reference). The decrease of substrate steady-state current caused by the addition of pesticide was used for evaluation. With this approach, 1.5 and 8.4 micrograms l-1 of paraoxon and heptenophos, respectively, can be detected in less than 3 min. These detection limits are similar as those obtained when analyses were performed using free cholinesterase and 10 min incubation with inhibitor.
Biosensing Techniques↗
Determination of organic acids, amino acids and saccharides by high-performance liquid chromatography and a postcolumn enzyme reactor with amperometric detection.
A technique for the determination of organic acids, amino acids and sugars is described. The compounds of interest are separated by high-performance liquid chromatography (HPLC) and converted on-line by immobilized enzymes. The enzymes employed are covalently bound to a synthetic carrier. Hydrogen peroxide, which is produced in the reaction with oxidases, makes possible the application of an electrochemical detector. This arrangement combines the separation efficiency of HPLC, the substrate specificity of enzymes and the high sensitivity of electrochemical detection. The enzymes act according to known reaction mechanisms, but coupling with HPLC leads to a promising extension in the field of biosensors. The simple pretreatment of the samples (often a dilution step is sufficient) allows a rapid analysis of foodstuffs and biological or clinical extracts. The examples presented demonstrate the very high sensitivity of the method with detection limits in the nano- to picomolar range and a wide field of application.
Amino Acids↗
Aggregation-induced Electrochemiluminescence of AgNCs Enhanced with AuNPs@MXene Composites for Ultrasensitive Detection of microRNA.
MXene, a two-dimensional nanomaterial, has metal conductivity, high electronegativity, functionalized with surface groups, which make it widely applicable in catalysis and biosensing. However, studies on the principle of enhanced electrochemiluminescence (ECL) by MXene composites and the improvement of their performance in catalyzing the ECL reaction are still in their infancy. In this study, gold nanoparticles (AuNPs) are obtained by mild reductive reduction and loaded in situ on the Ti3C2Tx MXene surface to form the composites (AuNPs@MXene). In oxygenated PBS test buffer, AuNPs@MXene enhance the ECL emission of silver nanoclusters (AgNCs) with aggregation-induced electrochemiluminescence (AIECL) properties as luminophore. Approximately 7.5-fold enhancement of ECL signals is obtained by using two ECL enhancement strategies: an efficient AIECL emitter and a co-reaction accelerator. The special nucleic acid structure with "Three Way Junction (TWJ)" enables an ultra-sensitive detection of microRNA, providing an efficient and ultra-sensitive method for microRNA detection. The biosensor achieves a wide detection range of microRNA-21 from 100 aM to 1 nM, with a low detection limit of 31 aM, and exhibits excellent stability, selectivity and high reproducibility in real samples.
MicroRNAs↗
Reagentless enzyme electrode for the determination of manganese through biocatalytic enhancement.
An amperometric enzyme electrode is described for the detection and determination of manganese(II). The biosensor is based on the stimulation by manganese of the aerobic oxidation of substrates by horseradish peroxidase. A mediator, 1,2-naphthoquinone, is used as the substrate and is incorporated with the enzyme into a carbon-paste electrode. The resulting electrode acts as an enzyme-based oxygen sensor, which is sensitive to manganese. Electrochemical control of enzyme activity is achieved through substrate promotion of catalysis. Enzyme modulation by manganese can be switched on and off or adjusted through the appropriate selection of the applied potential. Currents are generated due to the bioelectrocatalytic reduction of oxygen in response to the introduction of manganese sulfate. A sustained current is achieved which is dependent on manganese concentration. Concentrations of 0.5 microM manganese or greater can be measured, and the sensor is reversible, as demonstrated by manganese removal. Biological selectivity for manganese provides a sensor which does not respond to other divalent cations tested, with the possible exception of cobalt. Reagentless, continuous sensing is achieved through substrate cycling.
Catalysis↗
Surface-bound biomembranes incorporating receptors: electrochemical and structural characterization.
A generic method is described for forming surface-bound structures that incorporate protein receptors in a membrane-like environment. Silane reagents (octadecyltrichlorosilane and dimethyloctadecylchlorosilane) were used to produce primed substrates bearing full and partial monolayers, respectively. Biomembranes were formed by dialysis of detergent-solubilized membranes in the presence of two different alkylsilanized substrates: Si/SiO2 electrodes and glass microspheres. Electrochemical analysis of the capacitance was used to determine apparent thickness and degree of surface coverage at each stage in the deposition process. Elemental analysis on glass beads gave the hydrocarbon incorporation. Glass bead substrates were also examined by Fourier transform infrared spectroscopy to evaluate the alkylsilanized substrate before and after dialysis. Both vertebrate rhodopsin and the nicotinic acetylcholine receptor could be incorporated into structures with composition and dimensions similar to natural bilayer membranes. The techniques reported here are applicable for coupling membrane receptors to a variety of transducing substrates used in biosensors.
Animals↗
[Measurement of dopamine in rat striatum in vivo with a biomicroelectrode made from mixed plant tissue-carbon paste].
The mixed plant tissue-carbon paste electrode was prepared and their electrochemical characteristics were investigated. The sensitivity and selectivity of this bioelectrode were found to be good because of the utility in biocatalysis. It may work continuously with high stability for 10 h in vivo. The principal advantages of the new bioelectrodes are shorter in response time and longer in stability. These advantages meet the requirements of in vivo determination. Using these electrodes, the dopamine contents in rat striatum were measured by anodic stripping voltammetry. The drug-induced changes in dopamine levels were monitored. From the results, we can conclude that the biomicroelectrode is a very economic biosensor for its low cost and easiness to prepare and is a valuable tool for studying dopamine function. It will provide a good method for the evaluation of drug actions on dopamine neurones.
Animals↗