Monitoring the hemostasis process through the electrical characteristics of a graphene-based field-effect transistor

Hemostatic bioactivity and mechanism of novel Rubia cordifolia L.-derived carbon dots

Background: Rubia cordifolia L. (RCL) Carbonisata is a typical calcined natural medicinal plant, which has been used for thousands of years for hemostasis. At present, some studies have shown that some components of processed RCL Carbonisata can enhance hemostasis, but the specific hemostatic material basis is still unclear. Novel carbon dots (CDs) were obtained from Rubia cordifolia L. and named RCL-CDs to explore the hemostatic effect and mechanism of RCL-CDs obtained from Rubia cordifolia L. Methods: RCL-CDs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet visible spectroscopy (UV-Vis), fluorescence spectroscopy (FL), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The hemostatic effect of RCL-CDs was evaluated in a mouse tail amputation model and liver scratch model, and the hemostatic mechanism was explored using a capillary coagulation model and coagulation parameters. Results: The particle size distribution of RCL-CDs ranged from 1.74 nm to 9.78 nm, the maximum population was 3-4 nm, and the average particle size was 3.82 nm. The RCL-CDs were approximately spherical with a lattice spacing of 0.206 nm. The quantum yield (QY) of RCL-CDs is 1.09%, and there is a distinct diffraction peak at 2θ = 24.76°. The elemental composition of RCL-CDs was mainly C (65.28%), O (30.10%), and a small amount of N (4.62%). Pharmacological experiments showed that bleeding time and bleeding volume were reduced in mice treated with RCL-CDs. It is worth noting that the low-, medium- and high-dose RCL-CD groups can significantly reduce the blood loss, while the high-dose RCL-CD group can significantly reduce the bleeding time of the mouse tail amputation model and liver scratch model. Additionally, the fibrinogen level (FIB) and platelet counts (PLT) increased and prothrombin time (PT) decreased in rats after treatment with RCL-CDs. Conclusions: RCL-CDs have a significant hemostatic effect, and the mechanism may be exogenous coagulation and activation of fibrinogen. This explains the material basis of the hemostatic effect of RCLC and opens new avenues for more in-depth investigation. In addition, new insights into the potential biomedical applications of CDs in the field of nanohemostasis are provided and a solid foundation for the discovery of novel hemostatic agents is established.

Alzheimer's Disease Biomarker Detection Using Field Effect Transistor-Based Biosensor

Alzheimer's disease (AD) is closely related to neurodegeneration, leading to dementia and cognitive impairment, especially in people aged > 65 years old. The detection of biomarkers plays a pivotal role in the diagnosis and treatment of AD, particularly at the onset stage. Field-effect transistor (FET)-based sensors are emerging devices that have drawn considerable attention due to their crucial ability to recognize various biomarkers at ultra-low concentrations. Thus, FET is broadly manipulated for AD biomarker detection. In this review, an overview of typical FET features and their operational mechanisms is described in detail. In addition, a summary of AD biomarker detection and the applicability of FET biosensors in this research field are outlined and discussed. Furthermore, the trends and future prospects of FET devices in AD diagnostic applications are also discussed.

Review on two-dimensional material-based field-effect transistor biosensors: accomplishments, mechanisms, and perspectives

Field-effect transistor (FET) is regarded as the most promising candidate for the next-generation biosensor, benefiting from the advantages of label-free, easy operation, low cost, easy integration, and direct detection of biomarkers in liquid environments. With the burgeoning advances in nanotechnology and biotechnology, researchers are trying to improve the sensitivity of FET biosensors and broaden their application scenarios from multiple strategies. In order to enable researchers to understand and apply FET biosensors deeply, focusing on the multidisciplinary technical details, the iteration and evolution of FET biosensors are reviewed from exploring the sensing mechanism in detecting biomolecules (research direction 1), the response signal type (research direction 2), the sensing performance optimization (research direction 3), and the integration strategy (research direction 4). Aiming at each research direction, forward perspectives and dialectical evaluations are summarized to enlighten rewarding investigations.

Two-Dimensional Field-Effect Transistor Sensors: The Road toward Commercialization

The evolutionary success in information technology has been sustained by the rapid growth of sensor technology. Recently, advances in sensor technology have promoted the ambitious requirement to build intelligent systems that can be controlled by external stimuli along with independent operation, adaptivity, and low energy expenditure. Among various sensing techniques, field-effect transistors (FETs) with channels made of two-dimensional (2D) materials attract increasing attention for advantages such as label-free detection, fast response, easy operation, and capability of integration. With atomic thickness, 2D materials restrict the carrier flow within the material surface and expose it directly to the external environment, leading to efficient signal acquisition and conversion. This review summarizes the latest advances of 2D-materials-based FET (2D FET) sensors in a comprehensive manner that contains the material, operating principles, fabrication technologies, proof-of-concept applications, and prototypes. First, a brief description of the background and fundamentals is provided. The subsequent contents summarize physical, chemical, and biological 2D FET sensors and their applications. Then, we highlight the challenges of their commercialization and discuss corresponding solution techniques. The following section presents a systematic survey of recent progress in developing commercial prototypes. Lastly, we summarize the long-standing efforts and prospective future development of 2D FET-based sensing systems toward commercialization.

Electronic Sensing Platform (ESP) Based on Open-Gate Junction Field-Effect Transistor (OG-JFET) for Life Science Applications: Design, Modeling and Experimental Results

This paper presents a new field-effect sensor called open-gate junction gate field-effect transistor (OG-JFET) for biosensing applications. The OG-JFET consists of a p-type channel on top of an n-type layer in which the p-type serves as the sensing conductive layer between two ohmic contacted sources and drain electrodes. The structure is novel as it is based on a junction field-effect transistor with a subtle difference in that the top gate (n-type contact) has been removed to open the space for introducing the biomaterial and solution. The channel can be controlled through a back gate, enabling the sensor's operation without a bulky electrode inside the solution. In this research, in order to demonstrate the sensor's functionality for chemical and biosensing, we tested OG-JFET with varying pH solutions, cell adhesion (human oral neutrophils), human exhalation, and DNA molecules. Moreover, the sensor was simulated with COMSOL Multiphysics to gain insight into the sensor operation and its ion-sensitive capability. The complete simulation procedures and the physics of pH modeling is presented here, being numerically solved in COMSOL Multiphysics software. The outcome of the current study puts forward OG-JFET as a new platform for biosensing applications.

Aptamer-Based Solution-Gated Graphene Transistors for Highly Sensitive and Real-Time Detection of Thrombin Molecules

Thrombin is an important biomarker for various diseases and biochemical reactions. Rapid and real-time detection of thrombin that quickly neutralizes in early coagulation in the body has gained significant attention for its practical applications. Solution-gated graphene transistors (SGGTs) have been widely studied due to their higher sensitivity and low-cost fabrication for chemical and biological sensing applications. In this paper, the ssDNA aptamer with 29 bases was immobilized on the surface of the gate electrode to specifically recognize thrombin. The SGGT sensor achieved high sensitivity with a limit of detection (LOD) up to fM. The LOD was attributed to the amplification function of SGGTs and the suitable aptamer choice. The ssDNA configuration folding induced by thrombin molecules and the electropositivity of thrombin molecules could arouse the same electrical response of SGGTs, helping the device obtain a high sensitivity. The channel current variation of sensors had a good linear relationship with the logarithm of thrombin concentration in the range of 1 fM to 10 nM. The fabricated device also demonstrated a short response time to thrombin molecules, and the response time to the 1 fM thrombin molecules was about 150 s. In summary, the sensing strategy of aptamer-based SGGTs with high sensitivity and high selectivity has a good prospect in medical diagnosis.

Sensitive electrochemical biosensor combined with isothermal amplification for point-of-care COVID-19 tests

We report an electrochemical biosensor combined with recombinase polymerase amplification (RPA) for rapid and sensitive detection of severe acute respiratory syndrome coronavirus 2. The electrochemical biosensor based on a multi-microelectrode array allows the detection of multiple target genes by differential pulse voltammetry. The RPA reaction involves hybridization of the RPA amplicon with thiol-modified primers immobilized on the working electrodes, which leads to a reduction of current density as amplicons accumulate. The assay results in shorter "sample-to-answer" times than conventional PCR without expensive thermo-cycling equipment. The limits of detection are about 0.972 fg/μL (RdRP gene) and 3.925 fg/μL (N gene), which are slightly lower than or comparable to that of RPA assay results obtained by gel electrophoresis without post-amplification purification. The combination of electrochemical biosensors and the RPA assay is a rapid, sensitive, and convenient platform that can be potentially used as a point-of-care test for the diagnosis of COVID-19.

A Graphene-Based Enzymatic Biosensor Using a Common-Gate Field-Effect Transistor for L-Lactic Acid Detection in Blood Plasma Samples

Lactate is an important organic molecule that is produced in excess during anaerobic metabolism when oxygen is absent in the human organism. The concentration of this substance in the body can be related to several medical conditions, such as hemorrhage, respiratory failure, and ischemia. Herein, we describe a graphene-based lactate biosensor to detect the concentrations of L-lactic acid in different fluids (buffer solution and plasma). The active surface (graphene) of the device was functionalized with lactate dehydrogenase enzyme using different substances (Nafion, chitosan, and glutaraldehyde) to guarantee stability and increase selectivity. The devices presented linear responses for the concentration ranges tested in the different fluids. An interference study was performed using ascorbic acid, uric acid, and glucose, and there was a minimum variation in the Dirac point voltage during detection of lactate in any of the samples. The stability of the devices was verified at up to 50 days while kept in a dry box at room temperature, and device operation was stable until 12 days. This study demonstrated graphene performance to monitor L-lactic acid production in human samples, indicating that this material can be implemented in more simple and low-cost devices, such as flexible sensors, for point-of-care applications.