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At least 19 recordsLinked to original sources
PubMed1990

Sampling: a critical problem in biosensing.

Biosensing is widely recognised to be of potentially major importance to medicine and related fields, but in spite of a large number of impressive and important advances, widespread practical application has lagged. We examine the thesis that 'sampling' is a process which involves all of the phenomena which are associated with the transport of analyte molecules to the active sensor site, and that problems associated with this process are now the limiting factor in further use of many existing biosensors. We conclude that an integrated process of sampling and sensing should be emphasised in developing new biosensing systems, and propose several new approaches.

Biological Transport↗
PubMed1992

[Biosensing techniques for the laboratory medicine].

Biosensing techniques are utilized in micro analysis of the biological constituents with an integrated device. Their applications to laboratory medicine are of great interest. Recently, several types of micro electrodes or ion sensitive field effect transistors (ISOFET) were developed. For fabrication of the biosensor selection of the proper bio-element and transducer to assay our sample, is important. In this article we will indicate some items on the future prospect of biosensing techniques for laboratory medicine.

Biosensing Techniques↗
PubMed2026

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↗
PubMed2026

Repeat region engineering of Cas13a crRNA enables conformational gating-based autocatalytic CRISPR biosensing.

CrRNA engineering has emerged as a pivotal strategy for extending CRISPR-Cas13a biosensing. However, structural modulation of the direct repeat (DR) region remains exceptionally challenging due to its intricate architecture and the high energetic barrier of the Cas13a-crRNA interface, which is conventionally viewed as a rigid and immutable scaffold. Here, we demonstrate that the DR region is instead a programmable topological element with unexpected structural plasticity. By systematically engineering the DR through sequence insertion and structural splitting, we identified multiple DR variants that retain robust catalytic activity. Crucially, this topological reconfiguration enables Cas13a activity to be precisely gated by unmodified nucleic acid blockers, a level of regulation unattainable with the wild-type crRNA. Building on this flexible modulation, we developed Dre-CRISPR, a DR-engineered platform that couples target-triggered DR restoration to a self-reinforcing autocatalytic loop. This self-amplifying system provides a 2 × 106-fold sensitivity enhancement over nonamplified systems. Furthermore, the Dre-CRISPR platform extends the diagnostic scope of Cas13a to a broader spectrum of analytes, ranging from microRNAs to enzymatic activities and heavy metal ions. Our findings redefine the crRNA scaffold as a versatile signaling node and provide a generalizable framework for developing high-sensitivity, self-amplifying CRISPR biosensors through topology-driven guide RNA engineering.

CRISPR-Associated Proteins↗
PubMed1988

Feasibility of continuous glutamate monitoring in perfused retinal tissue with a potentiometric biosensing probe.

A potentiometric biosensing probe for glutamate has been evaluated as a possible tool to measure the release of glutamate from the isolated retina of Bufo marinus. This probe is based on carbon dioxide detection, following enzymatic conversion of glutamate to gamma-aminobutyric acid (GABA) via glutamic acid decarboxylase (GAD). Probe response characteristics of dynamic range, limit of detection, pH dependency, and selectivity are described. Probe modifications were required for sensor operation in an upside down configuration which was demanded by the need to mount and perfuse the retinal tissue directly at the sensor tip. Overall, these results indicate that this particular potentiometric biosensor is not well suited for direct glutamate measurements in retinal tissue because of pH incompatibility between the sensor and the tissue, and because of high background carbon dioxide levels released from the retina at the pH optimum of the probe. Despite this drawback, the sensor could be utilized to provide a continuous "downstream" monitor of glutamate levels during the course of an experiment, after pH buffering of tissue perfusate. Alternative approaches to probes more compatible with direct tissue measurements are discussed.

Animals↗
PubMed1985

The development and application of biosensing devices for bioreactor monitoring and control.

Presently, few of the reported (bio)chemical sensor devices have found application in fermentation monitoring and control. Although many devices with desirable selectivities have been reported, few have demonstrated reliability sufficient to encourage significant and widespread application. Chemical sensors (ion-selective electrodes, amperometric detectors, piezoelectric, field-effect transistors, semiconductor, Optrode and optoelectronic sensors), biosensors (based on potentiometric, amperometric, field-effect transistor and conductiometric detectors) and physical detection methods are reviewed with the aim of highlighting the problems of their application in this area. Physical detection principles appear to show promise as reliable and direct monitoring principles. However, even the more reliable discrete (bio)chemical sensor devices require the development of on-line flow sampling and autocalibration methods to demonstrate the necessary reliability. Biosensor devices appear most problematical and it is concluded that continued development of more direct biosensing principles is likely to prove most fruitful.

Biological Products↗
PubMed2026

Advances in Single-Molecule Immunoassay: From Counting Strategies to CRISPR-Enhanced Biosensing.

Single-molecule immunoassays (SMIs) overcome the sensitivity limitations of conventional bulk measurements by enabling a paradigm shift from analog to digital signal readouts, thereby facilitating highly sensitive quantification of ultra-low-abundance biomarkers for precision diagnostics. This review provides a systematic overview of recent advances in SMI technologies and the conceptual framework underlying their evolution. First, discretization strategies for single-molecule counting are classified into hard discretization, based on physical confinement, and soft discretization, based on spatiotemporal isolation, within heterogeneous and homogeneous assay systems, respectively. The fundamental mechanisms by which these strategies mitigate diffusion limitations and enhance signal-to-noise ratios are discussed. Second, the integration of SMIs with CRISPR-based diagnostic systems (CRISPR-dx) is examined, with particular emphasis on their complementary roles in target recognition and signal amplification. Finally, recent applications of SMIs in the diagnosis of oncological, neurological, infectious, and cardiovascular diseases are summarized, along with a critical discussion of current engineering challenges and future directions toward clinical translation.

Immunoassay↗
PubMed1992

A lysine dehydrogenase-based electrode for biosensing of L-lysine.

An amperometric biosensor for L-lysine based on the recently isolated enzyme lysine dehydrogenase is described. Immobilization of the enzyme onto a platinum electrode is achieved via entrapment within a gelatin support on a cellulose membrane. Anodic detection (at 0.4 V vs. Ag/AgCl) is facilitated by the presence of a redox-mediating ferricyanide ion. The effect of experimental variables such as pH, enzyme loading, applied potential, cofactor and mediator concentrations were evaluated in order to optimize the analytical performance. A detection limit of 7 x 10(-8) M, and linearity up to 7 x 10(-4) M are reported. The fast response permits adaptation for flow injection operation with good precision (RSD = 1.9%) and high sample throughout (40 samples per hour). The high specificity offered by this new enzyme is indicated by the lack of interference by other L-amino acids, alcohols or carbohydrates.

Amino Acid Oxidoreductases↗
PubMed1992

Biosensors and flow injection analysis.

Combining flow injection analysis with a biosensor is a novel biosensing process which has allowed speedy and accurate analysis. Diagnostic analysis is the most important application for biosensing flow injection analysis, but other applications include bioprocess monitoring, analysis of food and agricultural products, as well as environmental analysis. In addition, the analysis of compounds, such as explosives and abused drugs, and monitoring of Salmonella, the microorganism that causes food poisoning, have been reported.

Animals↗
PubMed2025

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↗
PubMed1990

Evaluation of neuron-based sensing with the neurotransmitter serotonin.

Results are presented on the development of a novel biosensor which will use neurons or neuronal components as both the recognition elements and primary transducers for analyte quantitation. This concept is demonstrated and evaluated by exposing identified neurons from the visceral ganglia of the pond snail Limnea stagnalis to the model analyte serotonin. Experiments reveal a reversible, concentration-dependent increase in the rate of spontaneous action potential generation, over a concentration range of four orders of magnitude. Studies with the antagonist methysergide verify that this response is mediated through serotonin-sensitive receptors. Exposure of the neurons to serotonin causes the firing frequency to rapidly increase to a maximum and then slowly diminish to a sub-optimal level. It was found that the maximum frequency provides an indication of chemical concentration that is repeatable. Data are also presented which further advance the field of neuronal biosensing by demonstrating both the effects of cell to cell variability on response reproducibility and the effects of the desensitizing response on the operation of a neuron-based sensor in both a continuous and discontinuous mode.

Action Potentials↗
PubMed1991

Current developments in optical biochemical sensors.

By combining modern fibre optics and opto-electronic instrumentation with chemical and biochemical reagent systems, it has become possible to fabricate optical biosensors. The current state of the art in this development is reviewed in this paper. Many developments describe selective and sensitive methods for sensing bioanalytes and it is likely that such a development will continue to be a very active area of analytical research. However, these biosensing devices can be regarded as successful only if their practicality and reliability can be demonstrated.

Albumins↗
PubMed1992

Comparison of colloidal gold electrode fabrication methods: the preparation of a horseradish peroxidase enzyme electrode.

In order to prepare biosensing electrodes which respond to hydrogen peroxide, horseradish peroxidase has been adsorbed to colloidal gold sols and electrodes prepared by deposition of these enzyme-gold sols onto glassy carbon using three methods: evaporation, electrodeposition and electrolyte deposition. In the latter method the enzyme-gold sol is applied to the surface of a glassy carbon disk electrode followed by an equal volume of 2 mM CaCl2. The electrolyte causes the sol to precipitate on the electrode surface, producing an immobilized enzyme electrode. Satisfactory electrodes which gave an electrochemical response to hydrogen peroxide in the presence of the electron transfer mediator ferrocenecarboxylic acid were produced by all three methods. Evaporation of horseradish peroxidase-gold sols produced electrodes with the best reproducibility and the widest linear amperometric response range. These electrodes can also easily be stored in a dry state. Although not as good as evaporation, electrodeposition also produced satisfactory electrodes. Electro-deposition provides the added advantage that it lends itself to the preparation of multi-enzyme/multi-analyte electrodes by the adsorption of different enzymes to separate gold sols, followed by sequential electrodeposition onto discrete areas of a multichannel electrode.

Biosensing Techniques↗
PubMed2026

Engineering bubble structures as Cas12a activators for highly sensitive monitoring of WRN helicase function.

The Werner syndrome helicase (WRN) is a critical synthetic lethal target in microsatellite instability cancers, essential for resolving complex genomic structures like replication bubbles and R-loops. However, strategies to simultaneously discriminate WRN activity on DNA versus DNA-RNA substrates in living cells are lacking. Here, we developed a structure-specific CRISPR/Cas12a biosensing strategy to visualize WRN functional activity by engineering bubble-structure probes. These probes were rationally designed to structurally mimic DNA replication bubbles and R-loop associated DNA-RNA hybrids. Upon specific unwinding by WRN, the probes release a sequestered activator strand that triggers Cas12a trans-cleavage, effectively converting the unwinding event into an amplified fluorescent signal. This assay achieves low picomolar sensitivity (LODs: 5.6-6.0 pM) and exceptional selectivity against homologous RecQ helicases. Uniquely, this strategy enables the parallel quantification of WRN activity on both substrate types, providing insights into distinct WRN-mediated pathways for resolving genomic stress. We further demonstrated the strategy's utility by visualizing endogenous WRN dynamics in living cells and profiling the efficacy of small-molecule inhibitors. This work offers a powerful molecular toolkit for dissecting WRN biology and facilitating high-throughput drug screening in targeted cancer therapy.

Werner Syndrome Helicase↗
PubMed1989

Conductometric transducers for enzyme-based biosensors.

The use of alternating current conductometric transducers in biosensing devices has been investigated for urea and D-amino acid sensors using the enzyme systems urease and D-amino acid oxidase/catalase. Transducers with copper and platinum electrodes were constructed and characterized, and two enzyme immobilization methods were tested. Detection limits of 1 x 10(-6)M and linear ranges of 2 orders of magnitude were routinely achieved for these model sensors with enzymes covalently immobilized on collagen films.

Amino Acids↗
PubMed2026

Design and optimization of a kinase-controlled allosteric switch.

Post-translational control enables rapid and precise regulation of cell behavior. Despite these advantages, general strategies to build phosphorylation-based synthetic circuits are limited. Here we reasoned that engineered allostery, a technique that has been applied to design light- and chemically gated protein switches, could also be used to engineer phosphorylation-controlled protein switches (phospho-switches). Using an allosterically controllable Gal4 transcription factor as a scaffold, we show that a classic kinase Förster resonance energy transfer biosensor architecture can be used as a starting point for phospho-switch design. We optimize all features of the phospho-switch to develop an ERK-controlled transcription factor with a 20-fold phosphorylation-dependent change in transcriptional output. The resulting synthetic ERK-responsive transcription factor responds with comparable sensitivity to the c-fos promoter and reveals spatial ERK signaling patterns in mammalian developmental organoids. We further show that our switch architecture can be generalized to other input kinases and allosterically controlled targets. This work provides a general platform for a new generation of kinase-responsive tools for biosensing and synthetic biology applications.

Allosteric Regulation↗