Biosensing based on field-effect transistors (FET): Recent progress and challenges

2D Materials in Advanced Electronic Biosensors for Point-of-Care Devices

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.

A rapid and ultrasensitive cardiac troponin I aptasensor based on an ion-sensitive field-effect transistor with extended gate

Acute myocardial infarction (AMI) is a life-threatening disease with a short course and a high mortality rate. However, it is still a great challenge to achieve the on-site diagnosis of this disease within minutes, meaning there is an urgent need to develop an efficient technology for realizing the rapid diagnosis and early warning of AMI in clinical emergencies. In this study, an ultrasensitive electrochemical aptasensor based on an extended-gate ion-sensitive field-effect transistor (EGISFET) was designed to achieve the quantitative assay of cardiac troponin I (cTnI), which is a highly sensitive and specific biomarker of AMI, within only 5 min. The EGISFET exhibits extremely high detection sensitivity due to its separated structure with a large sensing area and the surface-modified Prussian blue-gold nanoparticles (PB-AuNPs) composite, which serves as a signal magnifier and DNA loading platform for good electrocatalytic ability with a large specific area. Additionally, a target-induced strand-release strategy is proposed to shorten the recognition time of cTnI using a particular DNA strand. Under optimal conditions, the as-prepared aptasensor exhibits a wide linear range of 1-1000 pg/mL, an ultralow detection limit of 0.3 pg/mL, and reliable detection results in real serum samples. It is highly anticipated that this EGISFET-based aptasensor will have broad applications in the early warning and rapid diagnosis of AMI and other acute diseases in emergency treatment.

Label-Free Field Effect Transistors (FETs) for Fabrication of Point-of-Care (POC) Biomedical Detection Probes

Field effect transistors (FETs)-based detection probes are powerful platforms for quantification in biological media due to their sensitivity, ease of miniaturization, and ability to function in biological media. Especially, FET-based platforms have been utilized as promising probes for label-free detections with the potential for use in real-time monitoring. The integration of new materials in the FET-based probe enhances the analytical performance of the developed probes by increasing the active surface area, rejecting interfering agents, and providing the possibility for surface modification. Furthermore, the use of new materials eliminates the need for traditional labeling techniques, providing rapid and cost-effective detection of biological analytes. This review discusses the application of materials in the development of FET-based label-free systems for point-of-care (POC) analysis of different biomedical analytes from 2018 to 2024. The mechanism of action of the reported probes is discussed, as well as their pros and cons were also investigated. Also, the possible challenges and potential for the fabrication of commercial devices or methods for use in clinics were discussed.

A Portable Readout System for Biomarker Detection with Aptamer-Modified CMOS ISFET Array

Biosensors based on ion-sensitive field effect transistors (ISFETs) combined with aptamers offer a promising and convenient solution for point-of-care testing applications due to the ability for fast and label-free detection of a wide range of biomarkers. Mobile and easy-to-use readout devices for the ISFET aptasensors would contribute to further development of the field. In this paper, the development of a portable PC-controlled device for detecting aptamer-target interactions using ISFETs is described. The device assembly allows selective modification of individual ISFETs with different oligonucleotides. Ta2O5-gated ISFET structures were optimized to minimize trapped charge and capacitive attenuation. Integrated CMOS readout circuits with linear transfer function were used to minimize the distortion of the original ISFET signal. An external analog signal digitizer with constant voltage and superimposed high-frequency sine wave reference voltage capabilities was designed to increase sensitivity when reading ISFET signals. The device performance was demonstrated with the aptamer-driven detection of troponin I in both reference voltage setting modes. The sine wave reference voltage measurement method reduced the level of drift over time and enabled a lowering of the minimum detectable analyte concentration. In this mode (constant voltage 2.4 V and 10 kHz 0.1Vp-p), the device allowed the detection of troponin I with a limit of detection of 3.27 ng/mL. Discrimination of acute myocardial infarction was demonstrated with the developed device. The ISFET device provides a platform for the multiplexed detection of different biomarkers in point-of-care testing.

Gold nanostructure-enhanced immunosensing: ultra-sensitive detection of VEGF tumor marker for early disease diagnosis

We present an advanced electrochemical immunosensor designed to detect the vascular endothelial growth factor (VEGF) precisely. The sensor is constructed on a modified porous gold electrode through a fabrication process involving the deposition of silver and gold on an FTO substrate. Employing thermal annealing and a de-alloying process, the silver is eliminated from the electrode, producing a reproducible porous gold substrate. Utilizing a well-defined protocol, we immobilize the heavy-chain (VHH) antibody against VEGF on the gold substrate, facilitating VEGF detection through various electrochemical methods. Remarkably, this immunosensor performs well, featuring an impressive detection limit of 0.05 pg/mL and an extensive linear range from 0.1 pg/mL to 0.1 µg/mL. This emphasizes it's to measure biomarkers across a wide concentration spectrum precisely. The robust fabrication methodology in this research underscores its potential for widespread application, offering enhanced precision, reproducibility, and remarkable detection capabilities for the developed immunosensor.

Emerging biosensor probes for glycated hemoglobin (HbA1c) detection

Glycated hemoglobin (HbA1c), originating from the non-enzymatic glycosylation of βVal1 residues in hemoglobin (Hb), is an essential biomarker indicating average blood glucose levels over a period of 2 to 3 months without external environmental disturbances, thereby serving as the gold standard in the management of diabetes instead of blood glucose testing. The emergence of HbA1c biosensors presents affordable, readily available options for glycemic monitoring, offering significant benefits to small-scale laboratories and clinics. Utilizing nanomaterials coupled with high-specificity probes as integral components for recognition, labeling, and signal transduction, these sensors demonstrate exceptional sensitivity and selectivity in HbA1c detection. This review mainly focuses on the emerging probes and strategies integral to HbA1c sensor development. We discussed the advantages and limitations of various probes in sensor construction as well as recent advances in diverse sensing strategies for HbA1c measurement and their potential clinical applications, highlighting the critical gaps in current technologies and future needs in this evolving field.

Dual-channel fluorescent sensors based on chitosan-coated Mn-doped ZnS micromaterials to detect ampicillin

The global threat of antibiotic resistance has increased the importance of the detection of antibiotics. Conventional methods to detect antibiotics are time-consuming and require expensive specialized equipment. Here, we present a simple and rapid biosensor for detecting ampicillin, a commonly used antibiotic. Our method is based on the fluorescent properties of chitosan-coated Mn-doped ZnS micromaterials combined with the β-lactamase enzyme. The biosensors exhibited the highest sensitivity in a linear working range of 13.1-72.2 pM with a limit of detection of 8.24 pM in deionized water. In addition, due to the biological specificity of β-lactamase, the proposed sensors have demonstrated high selectivity over penicillin, tetracycline, and glucose through the enhancing and quenching effects at wavelengths of 510 nm and 614 nm, respectively. These proposed sensors also showed promising results when tested in various matrices, including tap water, bottled water, and milk. Our work reports for the first time the cost-effective (Mn:ZnS)Chitosan micromaterial was used for ampicillin detection. The results will facilitate the monitoring of antibiotics in clinical and environmental contexts.

Peptide-Based Flavivirus Biosensors: From Cell Structure to Virological and Serological Detection Methods

In tropical and developing countries, mosquito-borne diseases by flaviviruses pose a serious threat to public health. Early detection is critical for preventing their spread, but conventional methods are time-consuming and require skilled technicians. Biosensors have been developed to address this issue, but cross-reactivity with other flaviviruses remains a challenge. Peptides are essentially biomaterials used in diagnostics that allow virological and serological techniques to identify flavivirus selectively. This biomaterial originated as a small protein consisting of two to 50 amino acid chains. They offer flexibility in chemical modification and can be easily synthesized and applied to living cells in the engineering process. Peptides could potentially be developed as robust, low-cost, sensitive, and selective receptors for detecting flaviviruses. However, modification and selection of the receptor agents are crucial to determine the effectiveness of binding between the targets and the receptors. This paper addresses two potential peptide nucleic acids (PNAs) and affinity peptides that can detect flavivirus from another target-based biosensor as well as the potential peptide behaviors of flaviviruses. The PNAs detect flaviviruses based on the nucleotide base sequence of the target's virological profile via Watson-Crick base pairing, while the affinity peptides sense the epitope or immunological profile of the targets. Recent developments in the functionalization of peptides for flavivirus biosensors are explored in this Review by division into electrochemical, optical, and other detection methods.

Synthesis of carbon nanotubes-chitosan nanocomposite and immunosensor fabrication for myoglobin detection: An acute myocardial infarction biomarker

The use of single-walled carbon nanotubes (SWCNTs) in biomedical applications is limited due to their inability to disperse in aqueous solutions. In this study, dispersed -COOH functionalized CNTs with N-succinylated chitosan (CS), greatly increasing the water solubility of CNTs and forming a uniformly dispersed nanocomposite solution of CNTs@CS. Coupling reagent EDC/NHS was used as a linker with the -COOH groups present on the N-succinylated chitosan which significantly improved the affinity of the CNTs for biomolecules. Myoglobin (Mb) is a promising biomarker for the precise assessment of cardiovascular risk, type 2 diabetes, metabolic syndrome, hypertension and several types of cancer. A high level of Mb can be used to diagnose the mentioned pathogenic diseases. The CNTs@CS-FET demonstrates superior sensing performance for Mb antigen fortified in buffer, with a wide linear range of 1 to 4000 ng/mL. The detection limit of the developed Mb immunosensor was estimated to be 4.2 ng/mL. The novel CNTs@CS-FET immunosensor demonstrates remarkable capability in detecting Mb without being affected by interferences from nonspecific antigens. Mb spiked serum showed a recovery rate of 100.262 to 118.55 % indicating great promise for Mb detection in clinical samples. The experimental results confirmed that the CNTs@CS-FET immunosensor had excellent selectivity, reproducibility and storage stability.

Application of CRISPR/Cas13a-based biosensors in serum marker detection

The detection of serum markers is important for the early diagnosis and monitoring of diseases, but conventional detection methods have the problem of low specificity or sensitivity. CRISPR/Cas13a-based biosensors have the characteristics of simple detection methods and high sensitivity, which have a certain potential to solve the problems of conventional detection. This paper focuses on the research progress of CRISPR/Cas13a-based biosensors in serum marker detection, introduces the principles and applications of fluorescence, electrochemistry, colorimetric, and other biosensors based on CRISPR/Cas13a in the detection of serum markers, compares and analyzes the differences between the above CRISPR/Cas13a-based biosensors, and looks forward to the future development direction of CRISPR/Cas13a-based biosensors.

Label-Free Metal-Oxide Transistor Biosensors for Metabolite Detection in Human Saliva

Metabolites are essential molecules involved in various metabolic processes, and their deficiencies and excessive concentrations can trigger significant physiological consequences. The detection of multiple metabolites within a non-invasively collected biofluid could facilitate early prognosis and diagnosis of severe diseases. Here, a metal oxide heterojunction transistor (HJ-TFT) sensor is developed for the label-free, rapid detection of uric acid (UA) and 25(OH)Vitamin-D3 (Vit-D3) in human saliva. The HJ-TFTs utilize a solution-processed In2 O3 /ZnO channel functionalized with uricase enzyme and Vit-D3 antibody for the selective detection of UA and Vit-D3, respectively. The ultra-thin tri-channel architecture facilitates strong coupling between the electrons transported along the buried In2 O3 /ZnO heterointerface and the electrostatic perturbations caused by the interactions between the surface-immobilized bioreceptors and target analytes. The biosensors can detect a wide range of concentrations of UA (from 500 nm to 1000 µM) and Vit-D3 (from 100 pM to 120 nm) in human saliva within 60 s. Moreover, the biosensors exhibit good linearity with the physiological concentration of metabolites and limit of detections of ≈152 nm for UA and ≈7 pM for Vit-D3 in real saliva. The specificity is demonstrated against various interfering species, including other metabolites and proteins found in saliva, further showcasing its capabilities.

CA19-9 and CEA biosensors in pancreatic cancer

Cancer is a complex pathophysiological condition causing millions of deaths each year. Early diagnosis is essential especially for pancreatic cancer. Existing diagnostic tools rely on circulating biomarkers such as Carbohydrate Antigen 19-9 (CA19-9) and Carcinoembryonic Antigen (CEA). Unfortunately, these markers are nonspecific and may be increased in a variety of disorders. Accordingly, diagnosis of pancreatic cancer generally involves more invasive approaches such as biopsy as well as imaging studies. Recent advances in biosensor technology have allowed the development of precise diagnostic tools having enhanced analytical sensitivity and specificity. Herein we examine these advances in the detection of cancer in general and in pancreatic cancer specifically. Furthermore, we highlight novel technologies in the measurement of CA19-9 and CEA and explore their future application in the early detection of pancreatic cancer.

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.

Ultrasensitive Detection of PSA Using Antibodies in Crowding Polyelectrolyte Multilayers on a Silicon Nanowire Field-Effect Transistor

Immunosensors based on field-effect transistors with nanowire channels (NWFETs) provide fast and real-time detection of a variety of biomarkers without the need for additional labels. The key feature of the developed immunosensor is the coating of silicon NWs with multilayers of polyelectrolytes (polyethylenimine (PEI) and polystyrene sulfonate (PSS)). By causing a macromolecular crowding effect, it ensures the "soft fixation" of the antibodies into the 3-D matrix of the oppositely charged layers. We investigated the interaction of prostate-specific antigen (PSA), a biomarker of prostate cancer, and antibodies adsorbed in the PEI and PSS matrix. In order to visualize the formation of immune complexes between polyelectrolyte layers using SEM and AFM techniques, we employed a second clone of antibodies labeled with gold nanoparticles. PSA was able to penetrate the matrix and concentrate close to the surface layer, which is crucial for its detection on the nanowires. Additionally, this provides the optimal orientation of the antibodies' active centers for interacting with the antigen and improves their mobility. NWFETs were fabricated from SOI material using high-resolution e-beam lithography, thin film vacuum deposition, and reactive-ion etching processes. The immunosensor was characterized by a high sensitivity to pH (71 mV/pH) and an ultra-low limit of detection (LOD) of 0.04 fg/mL for PSA. The response of the immunosensor takes less than a minute, and the measurement is carried out in real time. This approach seems promising for further investigation of its applicability for early screening of prostate cancer and POC systems.

Asymmetric Schottky Barrier-Generated MoS2/WTe2 FET Biosensor Based on a Rectified Signal

Field-effect transistor (FET) biosensors can be used to measure the charge information carried by biomolecules. However, insurmountable hysteresis in the long-term and large-range transfer characteristic curve exists and affects the measurements. Noise signal, caused by the interference coefficient of external factors, may destroy the quantitative analysis of trace targets in complex biological systems. In this report, a "rectified signal" in the output characteristic curve, instead of the "absolute value signal" in the transfer characteristic curve, is obtained and analyzed to solve these problems. The proposed asymmetric Schottky barrier-generated MoS2/WTe2 FET biosensor achieved a 105 rectified signal, sufficient reliability and stability (maintained for 60 days), ultra-sensitive detection (10 aM) of the Down syndrome-related DYRK1A gene, and excellent specificity in base recognition. This biosensor with a response range of 10 aM-100 pM has significant application potential in the screening and rapid diagnosis of Down syndrome.

Synthesis and Bioapplication of Emerging Nanomaterials of Hafnium

A significant amount of progress in nanotechnology has been made due to the development of engineered nanoparticles. The use of metallic nanoparticles for various biomedical applications has been extensively investigated. Biomedical research is highly focused on them because of their inert nature, nanoscale structure, and similar size to many biological molecules. The intrinsic characteristics of these particles, including electronic, optical, physicochemical, and surface plasmon resonance, that can be altered by altering their size, shape, environment, aspect ratio, ease of synthesis, and functionalization properties, have led to numerous biomedical applications. Targeted drug delivery, sensing, photothermal and photodynamic therapy, and imaging are some of these. The promising clinical results of NBTXR3, a high-Z radiosensitizing nanomaterial derived from hafnium, have demonstrated translational potential of this metal. This radiosensitization approach leverages the dependence of energy attenuation on atomic number to enhance energy-matter interactions conducive to radiation therapy. High-Z nanoparticle localization in tumor issue differentially increases the effect of ionizing radiation on cancer cells versus nearby healthy ones and mitigates adverse effects by reducing the overall radiation burden. This principle enables material multifunctionality as contrast agents in X-ray-based imaging. The physiochemical properties of hafnium (Z = 72) are particularly advantageous for these applications. A well-placed K-edge absorption energy and high mass attenuation coefficient compared to elements in human tissue across clinical energy ranges leads to significant attenuation. Chemical reactivity allows for variety in nanoparticle synthesis, composition, and functionalization. Nanoparticles such as hafnium oxide exhibit excellent biocompatibility due to physiochemical inertness prior to incidence with ionizing radiation. Additionally, the optical and electronic properties are applicable in biosensing, optical component coatings, and semiconductors. The wide interest has prompted extensive research in design and synthesis to facilitate property fine-tuning. This review summarizes synthetic methods for hafnium-based nanomaterials and applications in therapy, imaging, and biosensing with a mechanistic focus. A discussion and future perspective section highlights clinical progress and elaborates on current challenges. By focusing on factors impacting applicational effectiveness and examining limitations this review aims to support researchers and expedite clinical translation of future hafnium-based nanomedicine.

Sensitive and rapid detection of bacterial endotoxin with a functional carbon nanotube field-effect transistor biosensor

Endotoxin in the blood can cause unexplained fever, and even death due to endotoxemia and bacteremia. Rapid and sensitive detection of endotoxin has become a priority event to intervene in the occurrence of dangerous diseases in time. In this context, a carbon nanotubes-based field-effect transistor (CNTs FET) nanosensor is developed to realize the rapid, label-free and sensitive detection of endotoxin. The CNTs FET was fabricated by assembling the polymer-sorted high-purity semiconductor CNT films onto the sensing channel. In order to improve the detection sensitivity, carboxylated graphene quantum dots (cGQDs) were coupled to the CNT surface via the poly-l-lysine (PLL). After that, polymyxin B (PMB), which is highly specific for endotoxin, was covalently combined with cGQDs, thus enabling the capture and detection of endotoxin. The method not only displayed an extremely low level of limitation of detection in PBS (4.6 fg/mL) and serum (30.3 fg/mL), respectively, with superior resistance to interference, but also enabled the analysis of Gram-negative bacterial infections in blood samples in a short duration of time. Meanwhile, the receiver operating characteristic curve (ROC) proved the superior diagnostic accuracy of this method (AUC = 0.990). Considering its excellent performance, the constructed CNTs FET biosensor is a promising tool to provide early warning of disease for clinical Gram-negative bacteremia and endotoxemia.

Advances in Bioelectrode Design for Developing Electrochemical Biosensors

The critical performance factors such as selectivity, sensitivity, operational and storage stability, and response time of electrochemical biosensors are governed mainly by the function of their key component, the bioelectrode. Suitable design and fabrication strategies of the bioelectrode interface are essential for realizing the requisite performance of the biosensors for their practical utility. A multifaceted attempt to achieve this goal is visible from the vast literature exploring effective strategies for preparing, immobilizing, and stabilizing biorecognition elements on the electrode surface and efficient transduction of biochemical signals into electrical ones (i.e., current, voltage, and impedance) through the bioelectrode interface with the aid of advanced materials and techniques. The commercial success of biosensors in modern society is also increasingly influenced by their size (and hence portability), multiplexing capability, and coupling in the interface of the wireless communication technology, which facilitates quick data transfer and linked decision-making processes in real-time in different areas such as healthcare, agriculture, food, and environmental applications. Therefore, fabrication of the bioelectrode involves careful selection and control of several parameters, including biorecognition elements, electrode materials, shape and size of the electrode, detection principles, and various fabrication strategies, including microscale and printing technologies. This review discusses recent trends in bioelectrode designs and fabrications for developing electrochemical biosensors. The discussions have been delineated into the types of biorecognition elements and their immobilization strategies, signal transduction approaches, commonly used advanced materials for electrode fabrication and techniques for fabricating the bioelectrodes, and device integration with modern electronic communication technology for developing electrochemical biosensors of commercial interest.

Advances in lithographic techniques for precision nanostructure fabrication in biomedical applications

Nano-fabrication techniques have demonstrated their vital importance in technological innovation. However, low-throughput, high-cost and intrinsic resolution limits pose significant restrictions, it is, therefore, paramount to continue improving existing methods as well as developing new techniques to overcome these challenges. This is particularly applicable within the area of biomedical research, which focuses on sensing, increasingly at the point-of-care, as a way to improve patient outcomes. Within this context, this review focuses on the latest advances in the main emerging patterning methods including the two-photon, stereo, electrohydrodynamic, near-field electrospinning-assisted, magneto, magnetorheological drawing, nanoimprint, capillary force, nanosphere, edge, nano transfer printing and block copolymer lithographic technologies for micro- and nanofabrication. Emerging methods enabling structural and chemical nano fabrication are categorised along with prospective chemical and physical patterning techniques. Established lithographic techniques are briefly outlined and the novel lithographic technologies are compared to these, summarising the specific advantages and shortfalls alongside the current lateral resolution limits and the amenability to mass production, evaluated in terms of process scalability and cost. Particular attention is drawn to the potential breakthrough application areas, predominantly within biomedical studies, laying the platform for the tangible paths towards the adoption of alternative developing lithographic technologies or their combination with the established patterning techniques, which depends on the needs of the end-user including, for instance, tolerance of inherent limits, fidelity and reproducibility.

Rapid and simultaneous multiple detection of a tripledemic using a dual-gate oxide semiconductor thin-film transistor-based immunosensor

The simultaneous infection with a tripledemic-simultaneous infection with influenza A pH1N1 virus (Flu), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and respiratory syncytial virus (RSV)-necessitates the development of accurate and fast multiplex diagnostic tests. The coronavirus disease 2019 (COVID-19) pandemic has emphasized the importance of virus detection. Field-effect transistor (FET)-based immuno-biosensors have a short detection time and do not require labeling or polymerase chain reaction. This study demonstrates the rapid, sensitive detection of influenza A pH1N1, SARS-CoV-2, and RSV using a multiplex immunosensor based on a dual-gate oxide semiconductor thin-film transistor (TFT), a type of FET. The dual-gate oxide TFT was modified by adjusting both top and bottom gate insulators to improve capacitive coupling to approximately 120-fold amplification, exhibiting a high pH sensitivity of about 10 V/pH. The dual-gate oxide TFT-based immunosensor detected the target proteins (hemagglutinin (HA) protein of Flu, spike 1 (S1) protein of SARS-CoV-2, and fusion protein of RSV) of each virus, with a limit of detection of approximately 1 fg/mL. Cultured viruses in phosphate-buffered saline or artificial saliva and clinical nasopharynx samples were detected in 1-μL sample volumes within 60 s. This promising diagnosis could be potentially as point-of-care tests to facilitate a prompt response to future pandemics with high sensitivity and multiplexed detection without pretreatment.

The Application of Graphene Field-Effect Transistor Biosensors in COVID-19 Detection Technology: A Review

Coronavirus disease 2019 (COVID-19) is a disease caused by the infectious agent of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). The primary method of diagnosing SARS-CoV-2 is nucleic acid detection, but this method requires specialized equipment and is time consuming. Therefore, a sensitive, simple, rapid, and low-cost diagnostic test is needed. Graphene field-effect transistor (GFET) biosensors have become the most promising diagnostic technology for detecting SARS-CoV-2 due to their advantages of high sensitivity, fast-detection speed, label-free operation, and low detection limit. This review mainly focus on three types of GFET biosensors to detect SARS-CoV-2. GFET biosensors can quickly identify SARS-CoV-2 within ultra-low detection limits. Finally, we will outline the pros and cons of the diagnostic approaches as well as future directions.

Electrochemically-gated graphene broadband microwave waveguides for ultrasensitive biosensing

Identification of non-amplified DNA sequences and single-base mutations is essential for molecular biology and genetic diagnostics. This paper reports a novel sensor consisting of electrochemically-gated graphene coplanar waveguides coupled with a microfluidic channel. Upon exposure to analytes, propagation of electromagnetic waves in the waveguides is modified as a result of interactions with the fringing field and modulation of graphene dynamic conductivity resulting from electrostatic gating. Probe DNA sequences are immobilised on the graphene surface, and the sensor is exposed to DNA sequences which either perfectly match the probe, contain a single-base mismatch or are unrelated. By monitoring the scattering parameters at frequencies between 50 MHz and 50 GHz, unambiguous and reproducible discrimination of the different strands is achieved at concentrations as low as one attomole per litre (1 aM). By controlling and synchronising frequency sweeps, electrochemical gating, and liquid flow in the microfluidic channel, the sensor generates multidimensional datasets. Advanced data analysis techniques are utilised to take full advantage of the richness of the dataset. A classification accuracy >97% between all three sequences is achieved using different Machine Learning models, even in the presence of simulated noise and low signal-to-noise ratios. The sensor exceeds state-of-the-art sensitivity of field-effect transistors and microwave sensors for the identification of single-base mismatches.

Micro- and nanosystems for the detection of hemorrhagic fever viruses

Hemorrhagic fever viruses (HFVs) are virulent pathogens that can cause severe and often fatal illnesses in humans. Timely and accurate detection of HFVs is critical for effective disease management and prevention. In recent years, micro- and nano-technologies have emerged as promising approaches for the detection of HFVs. This paper provides an overview of the current state-of-the-art systems for micro- and nano-scale approaches to detect HFVs. It covers various aspects of these technologies, including the principles behind their sensing assays, as well as the different types of diagnostic strategies that have been developed. This paper also explores future possibilities of employing micro- and nano-systems for the development of HFV diagnostic tools that meet the practical demands of clinical settings.

Advances in field-effect biosensors towards point-of-use

The future of medical diagnostics calls for portable biosensors at the point of care, aiming to improve healthcare by reducing costs, improving access, and increasing quality-what is called the 'triple aim'. Developing point-of-care sensors that provide high sensitivity, detect multiple analytes, and provide real time measurements can expand access to medical diagnostics for all. Field-effect transistor (FET)-based biosensors have several advantages, including ultrahigh sensitivity, label-free and amplification-free detection, reduced cost and complexity, portability, and large-scale multiplexing. They can also be integrated into wearable or implantable devices and provide continuous, real-time monitoring of analytesin vivo, enabling early detection of biomarkers for disease diagnosis and management. This review analyzes advances in the sensitivity, parallelization, and reusability of FET biosensors, benchmarks the limit of detection of the state of the art, and discusses the challenges and opportunities of FET biosensors for future healthcare applications.

Single-molecular protein-based bioelectronics via electronic transport: fundamentals, devices and applications

Biomolecular electronics is a rapidly growing multidisciplinary field that combines biology, nanoscience, and engineering to bridge the two important fields of life sciences and molecular electronics. Proteins are remarkable for their ability to recognize molecules and transport electrons, making the integration of proteins into electronic devices a long sought-after goal and leading to the emergence of the field of protein-based bioelectronics, also known as proteotronics. This field seeks to design and create new biomolecular electronic platforms that allow for the understanding and manipulation of protein-mediated electronic charge transport and related functional applications. In recent decades, there have been numerous reports on protein-based bioelectronics using a variety of nano-gapped electrical devices and techniques at the single molecular level, which are not achievable with conventional ensemble approaches. This review focuses on recent advances in physical electron transport mechanisms, device fabrication methodologies, and various applications in protein-based bioelectronics. We discuss the most recent progress of the single or few protein-bridged electrical junction fabrication strategies, summarise the work on fundamental and functional applications of protein bioelectronics that enable high and dynamic electron transport, and highlight future perspectives and challenges that still need to be addressed. We believe that this specific review will stimulate the interdisciplinary research of topics related to protein-related bioelectronics, and open up new possibilities for single-molecule biophysics and biomedicine.

In Situ Monitoring of Aptamer-Protein Binding on a ZnO Surface Using Spectroscopic Ellipsometry

The dissolution of zinc oxide is investigated using spectroscopic ellipsometry to investigate its suitability as a platform for biosensing applications. The results indicate that once the ZnO surface has been functionalised, it is suitably protected, and no significant dissolving of the ZnO occurs. The binding kinetics of the SARS-CoV-2 spike protein on aptamer-functionalised zinc oxide surfaces are subsequently investigated. Values are extracted for the refractive index and associated optical constants for both the aptamer layer used and the protein itself. It is shown that upon an initial exposure to the protein, a rapid fluctuation in the surface density is observed. After around 20 min, this effect stabilises, and a fixed increase in the surface density is observed, which itself increases as the concentration of the protein is increased. This technique and setup are demonstrated to have a limit-of-detection down to 1 nanomole (nM) and display a linear response to concentrations up to 100 nM.

Emerging Field-Effect Transistor Biosensors for Life Science Applications

Field-effect transistors (FETs) have gained significant interest and hold great potential as groundbreaking sensing technology in the fields of biosensing and life science research [...].

Label-Free Electrochemical Methods for Disease Detection

Label-free electrochemical biosensing leverages the advantages of label-free techniques, low cost, and fewer user steps, with the sensitivity and portability of electrochemical analysis. In this review, we identify four label-free electrochemical biosensing mechanisms: (a) blocking the electrode surface, (b) allowing greater access to the electrode surface, (c) changing the intercalation or electrostatic affinity of a redox probe to a biorecognition unit, and (d) modulating ion or electron transport properties due to conformational and surface charge changes. Each mechanism is described, recent advancements are summarized, and relative advantages and disadvantages of the techniques are discussed. Furthermore, two avenues for gaining further diagnostic information from label-free electrochemical biosensors, through multiplex analysis and incorporating machine learning, are examined.

Recent Progress in Micro- and Nanotechnology-Enabled Sensors for Biomedical and Environmental Challenges

Micro- and nanotechnology-enabled sensors have made remarkable advancements in the fields of biomedicine and the environment, enabling the sensitive and selective detection and quantification of diverse analytes. In biomedicine, these sensors have facilitated disease diagnosis, drug discovery, and point-of-care devices. In environmental monitoring, they have played a crucial role in assessing air, water, and soil quality, as well as ensured food safety. Despite notable progress, numerous challenges persist. This review article addresses recent developments in micro- and nanotechnology-enabled sensors for biomedical and environmental challenges, focusing on enhancing basic sensing techniques through micro/nanotechnology. Additionally, it explores the applications of these sensors in addressing current challenges in both biomedical and environmental domains. The article concludes by emphasizing the need for further research to expand the detection capabilities of sensors/devices, enhance sensitivity and selectivity, integrate wireless communication and energy-harvesting technologies, and optimize sample preparation, material selection, and automated components for sensor design, fabrication, and characterization.

Ultra-Scaled Si Nanowire Biosensors for Single DNA Molecule Detection

In this study, we use NEGF quantum transport simulations to study the fundamental detection limit of ultra-scaled Si nanowire FET (NWT) biosensors. A N-doped NWT is found to be more sensitive for negatively charged analytes as explained by the nature of the detection mechanism. Our results predict threshold voltage shifts due to a single-charge analyte of tens to hundreds of mV in air or low-ionic solutions. However, with typical ionic solutions and SAM conditions, the sensitivity rapidly drops to the mV/q range. Our results are then extended to the detection of a single 20-base-long DNA molecule in solution. The impact of front- and/or back-gate biasing on the sensitivity and limit of detection is studied and a signal-to-noise ratio of 10 is predicted. Opportunities and challenges to reach down to single-analyte detection in such systems are also discussed, including the ionic and oxide-solution interface-charge screening and ways to recover unscreened sensitivities.

Aptamer-functionalized field-effect transistor biosensors for disease diagnosis and environmental monitoring

Nano-biosensors that are composed of recognition molecules and nanomaterials have been extensively utilized in disease diagnosis, health management, and environmental monitoring. As a type of nano-biosensors, molecular specificity field-effect transistor (FET) biosensors with signal amplification capability exhibit prominent advantages including fast response speed, ease of miniaturization, and integration, promising their high sensitivity for molecules detection and identification. With intrinsic characteristics of high stability and structural tunability, aptamer has become one of the most commonly applied biological recognition units in the FET sensing fields. This review summarizes the recent progress of FET biosensors based on aptamer functionalized nanomaterials in medical diagnosis and environmental monitoring. The structure, sensing principles, preparation methods, and functionalization strategies of aptamer modified FET biosensors were comprehensively summarized. The relationship between structure and sensing performance of FET biosensors was reviewed. Furthermore, the challenges and future perspectives of FET biosensors were also discussed, so as to provide support for the future development of efficient healthcare management and environmental monitoring devices.

Odorant-responsive biological receptors and electronic noses for volatile organic compounds with aldehyde for human health and diseases: A perspective review

Volatile organic compounds (VOCs) are gaseous chemicals found in ambient air and exhaled breath. In particular, highly reactive aldehydes are frequently found in polluted air and have been linked to various diseases. Thus, extensive studies have been carried out to elucidate disease-specific aldehydes released from the body to develop potential biomarkers for diagnostic purposes. Mammals possess innate sensory systems, such as receptors and ion channels, to detect these VOCs and maintain physiological homeostasis. Recently, electronic biosensors such as the electronic nose have been developed for disease diagnosis. This review aims to present an overview of natural sensory receptors that can detect reactive aldehydes, as well as electronic noses that have the potential to diagnose certain diseases. In this regard, this review focuses on eight aldehydes that are well-defined as biomarkers in human health and disease. It offers insights into the biological aspects and technological advances in detecting aldehyde-containing VOCs. Therefore, this review will aid in understanding the role of aldehyde-containing VOCs in human health and disease and the technological advances for improved diagnosis.

The Integration of Field Effect Transistors to Microfluidic Devices

Devices that integrate field effect transistors into microfluidic channels are becoming increasingly promising in the medical, environmental, and food realms, among other applications. The uniqueness of this type of sensor lies in its ability to reduce the background signals existing in the measurements, which interfere in obtaining good limits of detection for the target analyte. This and other advantages intensify the development of selective new sensors and biosensors with coupling configuration. This review work focused on the main advances in the fabrication and application of field effect transistors integrated into microfluidic devices as a way of identifying the potentialities that exist in these systems when used in chemical and biochemical analyses. The emergence of research on integrated sensors is not a recent study, although more recently the progress of these devices is more accentuated. Among the studies that used integrated sensors with electrical and microfluidic parts, those that investigated protein binding interactions seem to be the ones that expanded the most due, among other things, to the possibility of obtaining several physicochemical parameters involved in protein-protein interactions. Studies in this area have a great possibility of advancing innovations in sensors with electrical and microfluidic interfaces in new designs and applications.

Electrokinetic Enrichment and Label-Free Electrochemical Detection of Nucleic Acids by Conduction of Ions along the Surface of Bioconjugated Beads

In this paper, we report a method to integrate the electrokinetic pre-enrichment of nucleic acids within a bed of probe-modified microbeads with their label-free electrochemical detection. In this detection scheme, hybridization of locally enriched target nucleic acids to the beads modulates the conduction of ions along the bead surfaces. This is a fundamental advancement in that this mechanism is similar to that observed in nanopore sensors, yet occurs in a bed of microbeads with microscale interstices. In application, this approach has several distinct advantages. First, electrokinetic enrichment requires only a simple DC power supply, and in combination with nonoptical detection, it makes this method amenable to point-of-care applications. Second, the sensor is easy to fabricate and comprises a packed bed of commercially available microbeads, which can be readily modified with a wide range of probe types, thereby making this a versatile platform. Finally, the sensor is highly sensitive (picomolar) despite the modest 100-fold pre-enrichment we employ here by faradaic ion concentration polarization (fICP). Further gains are anticipated under conditions for fICP focusing that are known to yield higher enrichment factors (up to 100,000-fold enrichment). Here, we demonstrate the detection of 3.7 pM single-stranded DNA complementary to the bead-bound oligoprobe, following a 30 min single step of enrichment and hybridization. Our results indicate that a shift in the slope of a current-voltage curve occurs upon hybridization and that this shift is proportional to the logarithm of the concentration of target DNA. Finally, we investigate the proposed mechanism of sensing by developing a numerical simulation that shows an increase in ion flux through the bed of insulating beads, given the changes in surface charge and zeta potential, consistent with our experimental conditions.

Modern Electrochemical Biosensing Based on Nucleic Acids and Carbon Nanomaterials

To meet the requirements of novel therapies, effective treatments should be supported by diagnostic tools characterized by appropriate analytical and working parameters. These are, in particular, fast and reliable responses that are proportional to analyte concentration, with low detection limits, high selectivity, cost-efficient construction, and portability, allowing for the development of point-of-care devices. Biosensors using nucleic acids as receptors has turned out to be an effective approach for meeting the abovementioned requirements. Careful design of the receptor layers will allow them to obtain DNA biosensors that are dedicated to almost any analyte, including ions, low and high molecular weight compounds, nucleic acids, proteins, and even whole cells. The impulse for the application of carbon nanomaterials in electrochemical DNA biosensors is rooted in the possibility to further influence their analytical parameters and adjust them to the chosen analysis. Such nanomaterials enable the lowering of the detection limit, the extension of the biosensor linear response, or the increase in selectivity. This is possible thanks to their high conductivity, large surface-to-area ratio, ease of chemical modification, and introduction of other nanomaterials, such as nanoparticles, into the carbon structures. This review discusses the recent advances on the design and application of carbon nanomaterials in electrochemical DNA biosensors that are dedicated especially to modern medical diagnostics.

Challenges and perspectives of multi-virus biosensing techniques: A review

In the context of globalization, individuals have an increased chance of being infected by multiple viruses simultaneously, thereby highlighting the importance of developing multiplexed devices. In addition to sufficient sensitivity and rapid response, multi-virus sensing techniques are expected to offer additional advantages including high throughput, one-time sampling for parallel analysis, and full automation with data visualization. In this paper, we review the optical, electrochemical, and mechanical platforms that enable multi-virus biosensing. The working mechanisms of each platform, including the detection principle, transducer configuration, bio-interface design, and detected signals, are reviewed. The advantages and limitations, as well as the challenges in implementing various detection strategies in real-life scenarios, were evaluated. Future perspectives on multiplexed biosensing techniques are critically discussed. Earlier access to multi-virus biosensors will efficiently serve for immediate pandemic control, such as in emerging SARS-CoV-2 and monkeypox cases.

A Brief Review of Graphene-Based Biosensors Developed for Rapid Detection of COVID-19 Biomarkers

The prevalence of mutated species of COVID-19 antigens has provided a strong impetus for identifying a cost-effective, rapid and facile strategy for identifying the viral loads in public places. The ever-changing genetic make-up of SARS-CoV-2 posts a significant challenfge for the research community to identify a robust mechanism to target, bind and confirm the presence of a viral load before it spreads. Synthetic DNA constructs are a novel strategy to design complementary DNA sequences specific for antigens of interest as in this review's case SARS-CoV-2 antigens. Small molecules, complementary DNA and protein-DNA complexes have been known to target analytes in minimal concentrations. This phenomenon can be exploited by nanomaterials which have unique electronic properties such as ballistic conduction. Graphene is one such candidate for designing a device with a very low LOD in the order of zeptomolar and attomolar concentrations. Surface modification will be the significant aspect of the device which needs to have a high degree of sensitivity at the same time as providing a rapid signaling mechanism.

PEDOT-Polyamine-Based Organic Electrochemical Transistors for Monitoring Protein Binding

The fabrication of efficient organic electrochemical transistors (OECTs)-based biosensors requires the design of biocompatible interfaces for the immobilization of biorecognition elements, as well as the development of robust channel materials to enable the transduction of the biochemical event into a reliable electrical signal. In this work, PEDOT-polyamine blends are shown as versatile organic films that can act as both highly conducting channels of the transistors and non-denaturing platforms for the construction of the biomolecular architectures that operate as sensing surfaces. To achieve this goal, we synthesized and characterized films of PEDOT and polyallylamine hydrochloride (PAH) and employed them as conducting channels in the construction of OECTs. Next, we studied the response of the obtained devices to protein adsorption, using glucose oxidase (GOx) as a model system, through two different strategies: The direct electrostatic adsorption of GOx on the PEDOT-PAH film and the specific recognition of the protein by a lectin attached to the surface. Firstly, we used surface plasmon resonance to monitor the adsorption of the proteins and the stability of the assemblies on PEDOT-PAH films. Then, we monitored the same processes with the OECT showing the capability of the device to perform the detection of the protein binding process in real time. In addition, the sensing mechanisms enabling the monitoring of the adsorption process with the OECTs for the two strategies are discussed.

Study on the Simulation of Biosensors Based on Stacked Source Trench Gate TFET

In order to detect biomolecules, a biosensor based on a dielectric-modulated stacked source trench gate tunnel field effect transistor (DM-SSTGTFET) is proposed. The stacked source structure can simultaneously make the on-state current higher and the off-state current lower. The trench gate structure will increase the tunneling area and tunneling probability. Technology computer-aided design (TCAD) is used for the sensitivity study of the proposed structured biosensor. The results show that the current sensitivity of the DM-SSTGTFET biosensor can be as high as 10⁸, the threshold voltage sensitivity can reach 0.46 V and the subthreshold swing sensitivity can reach 0.8. As a result of its high sensitivity and low power consumption, the proposed biosensor has highly promising prospects.

Two-Dimensional Transition Metal Dichalcogenide Based Biosensors: From Fundamentals to Healthcare Applications

There has been an exponential surge in reports on two-dimensional (2D) materials ever since the discovery of graphene in 2004. Transition metal dichalcogenides (TMDs) are a class of 2D materials where weak van der Waals force binds individual covalently bonded X-M-X layers (where M is the transition metal and X is the chalcogen), making layer-controlled synthesis possible. These individual building blocks (single-layer TMDs) transition from indirect to direct band gaps and have fascinating optical and electronic properties. Layer-dependent opto-electrical properties, along with the existence of finite band gaps, make single-layer TMDs superior to the well-known graphene that paves the way for their applications in many areas. Ultra-fast response, high on/off ratio, planar structure, low operational voltage, wafer scale synthesis capabilities, high surface-to-volume ratio, and compatibility with standard fabrication processes makes TMDs ideal candidates to replace conventional semiconductors, such as silicon, etc., in the new-age electrical, electronic, and opto-electronic devices. Besides, TMDs can be potentially utilized in single molecular sensing for early detection of different biomarkers, gas sensors, photodetector, and catalytic applications. The impact of COVID-19 has given rise to an upsurge in demand for biosensors with real-time detection capabilities. TMDs as active or supporting biosensing elements exhibit potential for real-time detection of single biomarkers and, hence, show promise in the development of point-of-care healthcare devices. In this review, we provide a historical survey of 2D TMD-based biosensors for the detection of bio analytes ranging from bacteria, viruses, and whole cells to molecular biomarkers via optical, electronic, and electrochemical sensing mechanisms. Current approaches and the latest developments in the study of healthcare devices using 2D TMDs are discussed. Additionally, this review presents an overview of the challenges in the area and discusses the future perspective of 2D TMDs in the field of biosensing for healthcare devices.

Recent Advances in Electrochemical Biosensors for Monitoring Animal Cell Function and Viability

Redox reactions in live cells are generated by involving various redox biomolecules for maintaining cell viability and functions. These qualities have been exploited in the development of clinical monitoring, diagnostic approaches, and numerous types of biosensors. Particularly, electrochemical biosensor-based live-cell detection technologies, such as electric cell-substrate impedance (ECIS), field-effect transistors (FETs), and potentiometric-based biosensors, are used for the electrochemical-based sensing of extracellular changes, genetic alterations, and redox reactions. In addition to the electrochemical biosensors for live-cell detection, cancer and stem cells may be immobilized on an electrode surface and evaluated electrochemically. Various nanomaterials and cell-friendly ligands are used to enhance the sensitivity of electrochemical biosensors. Here, we discuss recent advances in the use of electrochemical sensors for determining cell viability and function, which are essential for the practical application of these sensors as tools for pharmaceutical analysis and toxicity testing. We believe that this review will motivate researchers to enhance their efforts devoted to accelerating the development of electrochemical biosensors for future applications in the pharmaceutical industry and stem cell therapeutics.

Recent Advances, Opportunities, and Challenges in Developing Nucleic Acid Integrated Wearable Biosensors for Expanding the Capabilities of Wearable Technologies in Health Monitoring

Wearable biosensors are becoming increasingly popular due to the rise in demand for non-invasive, real-time monitoring of health and personalized medicine. Traditionally, wearable biosensors have explored protein-based enzymatic and affinity-based detection strategies. However, in the past decade, with the success of nucleic acid-based point-of-care diagnostics, a paradigm shift has been observed in integrating nucleic acid-based assays into wearable sensors, offering better stability, enhanced analytical performance, and better clinical applicability. This narrative review builds upon the current state and advances in utilizing nucleic acid-based assays, including oligonucleotides, nucleic acid, aptamers, and CRISPR-Cas, in wearable biosensing. The review also discusses the three fundamental blocks, i.e., fabrication requirements, biomolecule integration, and transduction mechanism, for creating nucleic acid integrated wearable biosensors.

Label-free and portable field-effect sensor for monitoring RT-LAMP products to detect SARS-CoV-2 in wastewater

The COVID-19 pandemic caused by the coronavirus SARS-CoV-2 has proven the need for developing reliable and affordable technologies to detect pathogens. Particularly, the detecting the genome in wastewater could be an indicator of the transmission rate to alert on new outbreaks. However, wastewater-based epidemiology remains a technological challenge to develop affordable technologies for sensing pathogens. In this work, we introduce a label-free and portable field-effect transistor (FET)-based sensor to detect N and ORF1ab genes of the SARS-CoV-2 genome. Our sensor integrates the reverse transcription loop-mediated isothermal amplification (RT-LAMP) reaction as a cost-effective molecular detection exhibiting high specificity. The detection relies upon pH changes, due to the RT-LAMP reaction products, which are detected through a simple, but effective, extended-gate FET sensor (EGFET). We evaluate the proposed device by measuring real wastewater samples to detect the presence of SARS-CoV-2 genome, achieving a limit of detection of 0.31 × 10⁻³ ng/μL for end-point measurement. Moreover, we find the ability of the sensor to perform real-time-like analysis, showing that the RT-LAMP reaction provides a good response after 15 min for concentrations as low as 0.37 ng/μL. Hence, we show that our EGFET sensor offers a powerful tool to detect the presence of the SARS-CoV-2 genome with a naked-eye method, in a straightforward way than the conventional molecular methods for wastewater analysis.

Graphitic Carbon Nitride and IGZO Bio-FET for Rapid Diagnosis of Myocardial Infarction

Acute myocardial infarction (AMI), commonly known as a heart attack, is a life-threatening condition that causes millions of deaths every year. In this study, a transistor-based biosensor is developed for rapid and sensitive detection of cardiac troponin-I (cTnI), a diagnostic biomarker of AMI. A biosensing technique based on a field effect transistor (FET), which uses indium gallium zinc oxide (IGZO) as an excellent semiconducting channel, is integrated with nanosheet materials to detect cTnI. Porous carbon nitride (PCN) decorated with gold nanoparticles (Au NPs) is used as a bridge between the solid-state device and the biorecognition element. We demonstrate that this biosensor is highly sensitive and has an experimental limit of detection of 0.0066 ng/mL and a dynamic range of 0.01 ng/mL-1000 ng/mL. This is the first report of a semiconducting metal oxide FET cardiac biomarker sensor combined with PCN for the detection of cTnI. The reported compact microsystem paves the way for rapid and inexpensive detection of cardiac biomarkers.

Sensors Based on the Carbon Nanotube Field-Effect Transistors for Chemical and Biological Analyses

Nano biochemical sensors play an important role in detecting the biomarkers related to human diseases, and carbon nanotubes (CNTs) have become an important factor in promoting the vigorous development of this field due to their special structure and excellent electronic properties. This paper focuses on applying carbon nanotube field-effect transistor (CNT-FET) biochemical sensors to detect biomarkers. Firstly, the preparation method, physical and electronic properties and functional modification of CNTs are introduced. Then, the configuration and sensing mechanism of CNT-FETs are introduced. Finally, the latest progress in detecting nucleic acids, proteins, cells, gases and ions based on CNT-FET sensors is summarized.

An Immunocolorimetric Sensing System for Highly Sensitive and High-Throughput Detection of BNP with Carbon-Gold Nanocomposites Amplification

Conventional immunocolorimetric sensing of biomolecules continues to be challenged with low sensitivity although its wide application as a diagnostic tool in medicine and biotechnology. Herein, we present a multifunctional immunocolorimetric sensing system for sensitive and high-throughput detection of B-type natriuretic peptide (BNP) with carbon-gold nanocomposite (CGNs) amplification. Using a “green” strategy, monodisperse carbon nanospheres (CNs) were successfully synthesized by glucose carbonization. A simple and efficient hydrothermal method was developed to assemble abundant gold nanoparticles (AuNPs) onto the surfaces of CNs. The resulting CGNs were characterized and utilized for biomarker detection with superior properties of easy manufacturing, good biocompatibility, satisfactory chemical stability, and high loading capacity for biomolecules. As a proof of concept, the as-prepared CGNs were conjugated with horseradish peroxidase-labeled antibody against BNP (CGNs@AntiBNP-HRP) functioning as the carrier, signal amplifier, and detector for the sensitive detection of BNP. Under optimal conditions, the established CGNs@AntiBNP-HRP immunoprobe remarkably enhanced the detection performance of BNP, achieving signal amplification of more than 9 times compared to the conventional method. Based on our self-developed bionic electronic eye (e-Eye) and CGNs@AntiBNP-HRP immunoprobe, the multifunctional sensing system displayed a wide dynamic linear range of 3.9–500 ng/mL and a LOD of 0.640 ng/mL for BNP detection with high specificity, good accuracy and reproducibility. This portable sensing system with enhanced performance demonstrates great potential for BNP detection in point of care applications, and offers a universal and reliable platform for in vitro biomarker detection.

A point-of-care biosensor for rapid and ultra-sensitive detection of SARS-CoV-2

In a recent study in Nature Biomedical Engineering, Wei's group constructed a field-effect transistor (FET) based on the "molecular electromechanical system" (MolEMS). MolEMS enabled FETs to specifically capture viral nucleic acids and efficiently transduce signals, achieving a rapid and ultra-sensitive detection of SARS-CoV-2.