Explore the vast range of titles available.

Since two‐dimensionalal (2D) materials have distinct chemical and physical properties, they are widely used in various sectors of modern technologies. In the domain of diagnostic biodevices, particularly for point‐of‐care (PoC) biomedical diagnostics, 2D‐based field‐effect transistor biosensors (bio‐FETs) demonstrate substantial potential. Here, in this review article, the operational mechanisms and detection capabilities of biosensing devices utilizing graphene, transition metal dichalcogenides (TMDCs), black phosphorus, and other 2D materials are addressed in detail. The incorporation of these materials into FET‐based biosensors offers significant advantages, including low detection limits (LOD), real‐time monitoring, label‐free diagnosis, and exceptional selectivity. The review also highlights the diverse applications of these biosensors, ranging from conventional to wearable devices, underscoring the versatility of 2D material‐based FET devices. Additionally, the review provides a comprehensive assessment of the limitations and challenges faced by these devices, along with insights into future prospects and advancements. Notably, a detailed comparison of FET‐based biosensors is tabulated along with various other biosensing platforms and their working mechanisms. Ultimately, this review aims to stimulate further research and innovation in this field while educating the scientific community about the latest advancements in 2D materials‐based biosensors. This article explores the working mechanism and detecting capacities of FET biosensors made from diverse 2D materials such as graphene, TMDCs, and black phosphorus. These materials enable the sensors to achieve low detection limits, real‐time monitoring, label‐free diagnostics, and great selectivity. It also discusses constraints and future directions, paving the path for advances in biosensor technology.

Extracellular vesicles (EVs) are complex biological nanoparticles endogenously secreted by all eukaryotic cells. EVs carry a specific molecular cargo of proteins, lipids, and nucleic acids derived from cells of origin and play a significant role in the physiology and pathology of cells, organs, and organisms. Upon release, they may be found in different body fluids that can be easily accessed noninvasive methodologies. Due to the unique information encoded in their molecular cargo, they may reflect the state of the parent cell and therefore EVs are recognized as a rich source of biomarkers for early diagnostics involving liquid biopsy. However, body fluids contain a mixture of EVs released by different types of healthy and diseased cells, making the detection of the EVs of interest very challenging. Recent research efforts have been focused on the detection and characterization of diagnostically relevant subpopulations of EVs, with emphasis on label-free methods that simplify sample preparation and are free of interfering signals. Therefore, in this paper, we review the recent progress of the label-free optical methods employed for the detection, counting, and morphological and chemical characterization of EVs. We will first briefly discuss the biology and functions of EVs, and then introduce different optical label-free techniques for rapid, precise, and nondestructive characterization of EVs such as nanoparticle tracking analysis, dynamic light scattering, atomic force microscopy, surface plasmon resonance spectroscopy, Raman spectroscopy, and SERS spectroscopy. In the end, we will discuss their applications in the detection of neurodegenerative diseases and cancer and provide an outlook on the future impact and challenges of these technologies to the field of liquid biopsy  EVs.

Complete blood count and differentiation of leukocytes (DIFF) belong to the most frequently performed laboratory diagnostic tests. Here, a flow cytometry‐based method for label‐free DIFF of untouched leukocytes by digital holographic microscopy on the rich phase contrast of peripheral leukocyte images, using highly controlled 2D hydrodynamic focusing conditions is reported. Principal component analysis of morphological characteristics of the reconstructed images allows classification of nine leukocyte types, in addition to different types of leukemia and demonstrates disappearance of acute myeloid leukemia cells in remission. To exclude confounding effects, the classification strategy is tested by the analysis of 20 blinded clinical samples. Here, 70% of the specimens are correctly classified with further 20% classifications close to a correct diagnosis. Taken together, the findings indicate a broad clinical applicability of the cytometry method for automated and reagent‐free diagnosis of hematological disorders. Label‐free differentiation of leukocytes is performed with a high‐throughput digital holographic microscope. The imaging‐based flow cytometry method allows to classify different types of leukemia and monitor the remission of leukemia patients. Blinded testing of clinical samples shows promising classification rates, which may lead to automated diagnosis of blood disorders without sample preparation.

In the present study, a highly sensitive and simple electrochemical (EC) aptasensor for the detection of serpin A12 as a novel biomarker of diabetes was developed on a platform where flower-like gold microstructures (FLGMs) are electrodeposited onto a disposable screen-printed carbon electrode. Meanwhile, serpin A12-specific thiolated aptamer was covalently immobilized on the FLGMs. The electrochemical activity of a fabricated aptasensor under various conditions were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Aptamer concentration, deposition time, self-assembly time, and incubation time were optimized for assay of serpin A12. The differential pulse voltammetry (DPV) was implemented for quantitative detection of serpin A12 in K [Fe (CN) ]/K [Fe (CN) ] solution (redox probe). The label-free aptasensor revealed a linear range of serpin A12 concentration (0.039-10 ng/mL), detection limit of 0.020 ng/mL (S/N=3), and 0.031 ng/mL in solution buffer and plasma, respectively. The results indicate that this aptasensor has a high sensitivity, selectivity, stability, and acceptable reproducibility for detection of serpin A12 in diabetic patients.

Accurate affinity assessments play an important role in drug discovery, screening, and efficacy evaluation. Label‐free affinity biosensors are recognized as a dependable and standard technology for addressing this challenge. This study constructs a free electron density gradient‐enhanced meta‐surface plasmon resonance (FED‐MSPR) biosensor through a finite‐difference time‐domain simulation model, the biosensor demonstrates superior detection performance in accurately determining affinity and kinetic rate constants. By controlling the dielectric properties of the metal on the surface of the nanocup arrays, the plasmon resonance effects are easily tuned without changing the nanostructure design. Compared with the single‐layer gold chip, the triple‐layer FED‐MSPR chip demonstrated a four‐fold improvement in resolution at the optimal resonance peak. Additionally, the sensitivity and figure of merit (FOM) of the multi‐layer chip increased by 3.5 and 7.99 times, respectively. Following modification with high‐ and low‐staggered carboxylation, the noise‐signal ratio and baseline stability of the real‐time kinetic curves based on these chips are significantly enhanced. The developed carboxylation FED‐MSPR platform is successfully used to perform affinity assays for Adalimumab and TNF‐α protein, resulting in favorable dynamic curves. These findings validate the proposed FED‐MSPR biosensor platform as cost‐effective, rapid, sensitive, and label‐free, facilitating real‐time quality control in drug development. This study proposes a free electron density gradient‐enhanced meta‐surface plasmon resonance (FED‐MSPR) biosensor with extraordinary detection performance in accurately determining affinity and kinetic rate constants. The developed carboxylation FED‐MSPR biosensor is successfully used to perform affinity assays for adalimumab and TNF‐α protein, validate the proposed FED‐MSPR biosensor platform as cost‐effective, rapid, sensitive, and label‐free, facilitating real‐time quality control in drug development.

Adenosine 5′-triphosphate (ATP) plays a crucial role as an extracellular signaling molecule in the central nervous system and is closely related to various nerve diseases. Therefore, label-free imaging of extracellular ATP dynamics and spatiotemporal analysis is crucial for understanding brain function. To decrease the limit of detection (LOD) of imaging extracellular ATP, we fabricated a redox-type label-free ATP image sensor by immobilizing glycerol-kinase (GK), L-α-glycerophosphate oxidase (LGOx), and horseradish peroxidase (HRP) enzymes in a polymer film on a gold electrode-modified potentiometric sensor array with a 37.3 µm-pitch. Hydrogen peroxide (H2O2) is generated through the enzymatic reactions from GK to LGOx in the presence of ATP and glycerol, and ATP can be detected as changes in its concentration using an electron mediator. Using this approach, the LOD for ATP was 2.8 µM with a sensitivity of 77 ± 3.8 mV/dec., under 10 mM working buffers at physiological pH, such as in in vitro experiments, and the LOD was great superior 100 times than that of the hydrogen ion detection-based image sensor. This redox-type ATP image sensor may be successfully applied for in vitro sensitive imaging of extracellular ATP dynamics in brain nerve tissue or cells.

Protein–ligand interactions are central to understanding biological mechanisms and drug discovery, yet conventional assays often rely on labeling or immobilization that can alter natural binding. Here, we introduce ultraviolet transient absorption microscopy (UV‐TAM), which directly detects binding through ligand‐induced changes in the excited‐state dynamics of tryptophan residues. Using a femtosecond deep‐UV pump and a near‐UV probe, UV‐TAM enables label‐free, in‐solution measurements with only microliter sample volumes. We demonstrate its capability using plasma proteins—bovine serum albumin and hemoglobin—with alkaloid ligands, berberine and palmatine. Binding events are clearly identified through time‐resolved spectral changes. Quantitative analysis of hemoglobin–alkaloid interactions yields dissociation constants in close agreement with isothermal titration calorimetry. UV‐TAM thus provides a robust, calibration‐free platform for studying protein interactions in solution, with significant potential for biochemical research and high‐throughput drug discovery. A femtosecond UV pump–probe microscope resolves binding‐induced changes in protein excited‐state dynamics and converts these intrinsic contrasts into an equilibrium affinity readout. By probing tryptophan responses directly in solution, the approach enables quantitative determination of dissociation constants without labeling or immobilization, offering a minimally perturbative platform for protein–ligand interaction analysis.

We developed a new label-free assay to evaluate the inhibition capacity of AX-024 by means of a new Point-of-Care (PoC) device for application in the development of new drugs in autoimmune diseases. The technology of PoC is based on interferometric optical detection method (IODM). For this purpose, we have optimized and developed an assay protocol whereby a Glutathione S-Transferase modified protein (GST-SH3.1), which contains a functional domain of a protein involved in T-cell activation, together with the AX-024 inhibitor has been studied. The chips used are a sensing surface based on nitrocellulose. We used streptavidin and a biotinylated peptide as links for the immobilization process on the sensing surface. The biotinylated peptide and AX-024 inhibitor compete for the same functional group of the GST-SH3.1 modified protein. When the inhibitor binds its binding site on GST-SH3.1, the biotinylated peptide cannot bind to its pocket on the protein. This competition reduces the total molecular mass of protein fixed onto the biosensor. In order to quantify the inhibition capacity of AX-024, several Ax-024:GST-SH3.1 ratios have been studied. We have compared the read-out signal for GST-SH3.1 protein not interfered by the drug, which served as a positive blank, and the response of the GST-SH3.1 modified protein blocked by the inhibitor. The technology has been correlated with confocal fluorescence microscopy.

Detection of tumor markers is important for cancer diagnosis. Field-effect transistors (FETs) are a promising method for the label-free detection of trace amounts of biomolecules. However, detection of electrically charged proteins using antibody-immobilized FETs is limited by ionic screening by the large probe molecules adsorbed to the transistor gate surface, reducing sensor responsiveness. Here, we investigated the effect of probe molecule size on the detection of a tumor marker, α-fetoprotein (AFP) using a FET biosensor. We demonstrated that the small receptor antigen binding fragment (Fab), immobilized on a sensing surface as small as 2–3 nm, offers a higher degree of sensitivity and a wider concentration range (100 pg/mL–1 μg/mL) for the FET detection of AFP in buffer solution, compared to the whole antibody. Therefore, the use of a small Fab probe molecule instead of a whole antibody is shown to be effective for improving the sensitivity of AFP detection in FET biosensors. Furthermore, we also demonstrated that a Fab-immobilized FET subjected to a blocking treatment, to avoid non-specific interactions, could sensitively and selectively detect AFP in human serum.

Establishing low‐cost, high‐throughput, simple, and accurate single nucleotide polymorphism (SNP) genotyping techniques is beneficial for understanding the intrinsic relationship between individual genetic variations and their biological functions on a genomic scale. Here, a straightforward and reliable single‐molecule approach is demonstrated for precise SNP authentication by directly measuring the fluctuations in electrical signals in an electronic circuit, which is fabricated from a high‐gain field‐effect silicon nanowire decorated with a single hairpin DNA, in the presence of different target DNAs. By simply comparing the proportion difference of a probe‐target duplex structure throughout the process, this study implements allele‐specific and accurate SNP detection. These results are supported by the statistical analyses of different dynamic parameters such as the mean lifetime and the unwinding probability of the duplex conformation. In comparison with conventional polymerase chain reaction and optical methods, this convenient and label‐free method is complementary to existing optical methods and also shows several advantages, such as simple operation and no requirement for fluorescent labeling, thus promising a futuristic route toward the next‐generation genotyping technique. A straightforward and reliable single‐molecule approach for precise single nucleotide polymorphism detection is developed through directly measuring the fluctuation of electrical signals in an electronic circuit, which is fabricated from a high‐gain field‐effect silicon nanowire decorated by a single hairpin DNA, in the presence of different target DNAs, promising a futuristic route toward the next‐generation genotyping technique.