Precise and Prompt Analyte Detection via Ordered Orientation of Receptor in WSe2-Based Field Effect Transistor

Nanomaterials-Based Field-Effect Transistor for Protein Sensing: New Advances

It is crucial for early stage medical diagnostics to identify disease biomarkers at ultralow concentrations. A wide range of analytes can be identified using low-dimensional materials to build highly sensitive, targeted, label-free, field-effect transistor (FET) biosensors. Two-dimensional (2D) materials are preferable for high-performance biosensing because of their dramatic change in resistivity upon analyte adsorption or biomarker detection, tunable electronic properties, high surface activities, adequate stability, and layer-dependent semiconducting properties. We give a succinct overview of interesting applications for protein sensing with various architectural styles, such as 2D transition metal dichalcogenides (TMDs)-based FETs that include carbon nanotubes (CNTs), graphene (Gr), reduced graphene oxide (rGr), 2D transition-metal carbides (MXene), and Gr/MXene heterostructures. Because it might enable individuals to perform better, this review will be an important contribution to the field of medical science. These achievements demonstrate point-of-care diagnostics' abilities to detect biomarkers at ultrahigh performance levels. A summary of the present opportunities and challenges appears in the conclusion.

A Novel Biosensing Approach: Improving SnS2 FET Sensitivity with a Tailored Supporter Molecule and Custom Substrate

The exclusive features of two-dimensional (2D) semiconductors, such as high surface-to-volume ratios, tunable electronic properties, and biocompatibility, provide promising opportunities for developing highly sensitive biosensors. However, developing practical biosensors that can promptly detect low concentrations of target analytes remains a challenging task. Here, a field-effect-transistor comprising n-type transition metal dichalcogenide tin disulfide (SnS2 ) is developed over the hexagonal boron nitride (h-BN) for the detection of streptavidin protein (Strep.) as a target analyte. A self-designed receptor based on the pyrene-lysine conjugated with biotin (PLCB) is utilized to maintain the sensitivity of the SnS2 /h-BN FET because of the π-π stacking. The detection capabilities of SnS2 /h-BN FET are investigated using both Raman spectroscopy and electrical characterizations. The real-time electrical measurements exhibit that the SnS2 /h-BN FET is capable of detecting streptavidin at a remarkably low concentration of 0.5 pm, within 13.2 s. Additionally, the selectivity of the device is investigated by measuring its response against a Cow-like serum egg white protein (BSA), having a comparative molecular weight to that of the streptavidin. These results indicate a high sensitivity and rapid response of SnS2 /h-BN biosensor against the selective proteins, which can have significant implications in several fields including point-of-care diagnostics, drug discovery, and environmental monitoring.

Low-Power Negative-Differential-Resistance Device for Sensing the Selective Protein via Supporter Molecule Engineering

Van der Waals (vdW) heterostructures composed of atomically thin two-dimensional (2D) materials have more potential than conventional metal-oxide semiconductors because of their tunable bandgaps, and sensitivities. The remarkable features of these amazing vdW heterostructures are leading to multi-functional logic devices, atomically thin photodetectors, and negative differential resistance (NDR) Esaki diodes. Here, an atomically thin vdW stacking composed of p-type black arsenic (b-As) and n-type tin disulfide (n-SnS2 ) to build a type-III (broken gap) heterojunction is introduced, leading to a negative differential resistance device. Charge transport through the NDR device is investigated under electrostatic gating to achieve a high peak-to-valley current ratio (PVCR), which improved from 2.8 to 4.6 when the temperature is lowered from 300 to 100 K. At various applied-biasing voltages, all conceivable tunneling mechanisms that regulate charge transport are elucidated. Furthermore, the real-time response of the NDR device is investigated at various streptavidin concentrations down to 1 pm, operating at a low biasing voltage. Such applications of NDR devices may lead to the development of cutting-edge electrical devices operating at low power that may be employed as biosensors to detect a variety of target DNA (e.g., ct-DNA) and protein (e.g., the spike protein associated with COVID-19).

Flexible Actuator Based on Conductive PAM Hydrogel Electrodes with Enhanced Water Retention Capacity and Conductivity

Conductive polyacrylamide (PAM) hydrogels with salts that act as electrolytes have been used as transparent electrodes with high elasticity in flexible electronic devices. Different types and contents of raw materials will affect their performance in all aspects. We tried to introduce highly hydratable salts into PAM hydrogels to improve their water retention capacity. Different salts can improve the water retention capacity of PAM hydrogels to a certain extent. In particular, PAM hydrogels containing higher concentrations of lithium chloride (LiCl) and calcium chloride (CaCl₂) showed an extremely strong water retention capacity and could retain about 90% and more than 98% of the initial water in the experimental environment at a temperature of 25 °C and a relative humidity of 60% RH, respectively. In addition, we conducted electrical conductivity tests on these PAM hydrogels with different salts. The PAM hydrogels containing LiCl also show outstanding conductivity, and the highest conductivity value can reach up to about 8 S/m. However, the PAM hydrogels containing CaCl₂, which also performed well in terms of their water retention capacity, were relatively common in terms of their electrical conductivity. On this basis, we attempted to introduce single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and graphene (GO) electronic conductors to enhance the electrical conductivity of the PAM hydrogels containing LiCl. The conductivity of the PAM hydrogels containing LiCl was improved to a certain extent after the addition of these electronic conductors. The highest electrical conductivity was about 10 S/m after we added the SWCNTs. This experimental result indicates that these electronic conductors can indeed enhance the electrical conductivity of PAM hydrogels to a certain extent. After a maximum of 5000 repeated tensile tests, the conductive hydrogel samples could still maintain their original morphological characteristics and conductivity. This means that these conductive hydrogel samples have a certain degree of system reliability. We made the PAM conductive hydrogels with high water retention and good conductivity properties into thin electrodes and applied them to an electric response flexible actuator with dielectric elastomer as the functional material. This flexible actuator can achieve a maximum area strain of 18% under an external voltage of 10 kV. This new composite hydrogels with high water retention and excellent conductivity properties will enable more possibilities for the application of hydrogels.

Hollow-Core Fiber-Based Biosensor: A Platform for Lab-in-Fiber Optical Biosensors for DNA Detection

In this paper, a novel platform for lab-in-fiber-based biosensors is studied. Hollow-core tube lattice fibers (HC-TLFs) are proposed as a label-free biosensor for the detection of DNA molecules. The particular light-guiding mechanism makes them a highly sensitive tool. Their transmission spectrum is featured by alternations of high and low transmittance at wavelength regions whose values depend on the thickness of the microstructured web composing the cladding around the hollow core. In order to achieve DNA detection by using these fibers, an internal chemical functionalization process of the fiber has been performed in five steps in order to link specific peptide nucleic acid (PNA) probes, then the functionalized fiber was used for a three-step assay. When a solution containing a particular DNA sequence is made to flow through the HC of the TLF in an ‘optofluidic’ format, a bio-layer is formed on the cladding surfaces causing a red-shift of the fiber transmission spectrum. By comparing the fiber transmission spectra before and after the flowing it is possible to identify the eventual formation of the layer and, therefore, the presence or not of a particular DNA sequence in the solution.

Aptamer-Based Sensors for Thrombin Detection Application

Thrombin facilitates the aggregation of platelet in hemostatic processes and participates in the regulation of cell signaling. Therefore, the development of thrombin sensors is conducive to comprehending the role of thrombin in the course of a disease. Biosensors based on aptamers screened by SELEX have exhibited superiority for thrombin detection. In this review, we summarized the aptamer-based sensors for thrombin detection which rely on the specific recognitions between thrombin and aptamer. Meanwhile, the unique advantages of different sensors including optical and electrochemical sensors were also highlighted. Especially, these sensors based on electrochemistry have the potential to be miniaturized, and thus have gained comprehensive attention. Furthermore, concerns about aptamer-based sensors for thrombin detection, prospects of the future and promising avenues in this field were also presented.

A Review of Transition Metal Dichalcogenides-Based Biosensors

Transition metal dichalcogenides (TMDCs) are widely used in biosensing applications due to their excellent physical and chemical properties. Due to the properties of biomaterial targets, the biggest challenge that biosensors face now is how to improve the sensitivity and stability. A lot of materials had been used to enhance the target signal. Among them, TMDCs show excellent performance in enhancing biosensing signals because of their metallic and semi-conducting electrical capabilities, tunable band gap, large specific surface area and so on. Here, we review different functionalization methods and research progress of TMDCs-based biosensors. The modification methods of TMDCs for biosensor fabrication mainly include two strategies: non-covalent and covalent interaction. The article summarizes the advantages and disadvantages of different modification strategies and their effects on biosensing performance. The authors present the challenges and issues that TMDCs need to be addressed in biosensor applications. Finally, the review expresses the positive application prospects of TMDCs-based biosensors in the future.