Donor effect dominated molybdenum disulfide/graphene nanostructure-based field-effect transistor for ultrasensitive DNA detection

Engineered molybdenum disulfide nanosheets as scavengers against oxidative stress inhibit ferroptosis to alleviate acute kidney injury

Acute kidney injury (AKI) is a common clinical kidney dysfunction associated with high morbidity, elevated mortality, and poor prognosis. It results from redox imbalance caused by abnormal excess production of endogenous reactive oxygen species (ROS) at the renal tubules, which in turn initiates a series of pathological processes, such as cellular apoptosis, necrosis, and ferroptosis, eventually leading to structural and functional impairment of the kidney. Thereinto, ferroptosis induced by the lethal accumulation of lipid peroxidation is extensively involved in renal damage. Nanotechnology-mediated therapeutic strategies to scavenge excessive ROS and thereby inhibit ferroptosis represents a promising strategy for AKI management. Herein, we report two engineered ultrathin molybdenum disulfide (MoS2) nanosheets (NSs) modified with polyvinylpyrrolidone (PVP) and bovine serum albumin (BSA), respectively, with excellent biocompatibility and antioxidative defense capability for AKI treatment. The engineered NSs, with a readily variable valence state of molybdenum ions, rescued cell viability by consuming various forms of cellular ROS and significantly facilitated glutathione peroxidase 4 (GPX4) expression to mitigate ferroptosis in renal tubular epithelial cells. In a glycerol-induced AKI mouse model, the PVP-MoS2 NSs were largely accumulated in the injured kidneys, where they provided robust antioxidative protection against ROS attack and suppressed the oxidative stress-induced inflammatory response, thereby maintaining normal kidney function. Of the two engineered NSs, PVP-MoS2 displayed superior biological stability and therapeutic effects and could thus serve as a powerful antioxidant platform for use in the treatment of AKI and other ROS-associated diseases. This study underscores the potential of two-dimensional nanomaterials in precisely treating AKI and other ferroptosis-related diseases.

The Versatility of Biological Field-Effect Transistor-Based Biosensors (BioFETs) in Point-of-Care Diagnostics: Applications and Future Directions for Peritoneal Dialysis Monitoring

Peritoneal dialysis (PD) is a vital treatment for end-stage renal disease patients, but its efficacy is often compromised by complications such as infections and peritoneal fibrosis. Biological field-effect transistors (BioFETs) present a promising solution for rapid, sensitive, and non-invasive detection of indicators and biomarkers associated with these complications, potentially enabling early intervention. However, BioFETs are yet to be adopted for PD monitoring. This review presents a forward-looking analysis of the capacity and potential integration of BioFETs into PD management systems, highlighting their capacity to monitor both routine indicators of dialysis efficiency and metabolic status, as well as specific biomarkers for complications such as inflammation and fibrosis. We examine the challenges in adapting BioFETs for PD applications, focusing on key areas for improvement, including sensitivity, specificity, stability, reusability, and clinical integration. Furthermore, we discuss various approaches to address these challenges, which are crucial for developing point-of-care (PoC) and multiplexed wearable devices. These advancements could facilitate continuous, precise, and user-friendly monitoring, potentially revolutionizing PD complication management and enhancing patient care.

Amplification-free detection of Mycobacterium tuberculosis using CRISPR-Cas12a and graphene field-effect transistors

Current molecular tests for tuberculosis (TB), such as whole genome sequencing and Xpert Mycobacterium tuberculosis/rifampicin resistance assay, exhibit limited sensitivity and necessitate the pre-amplification step of target DNA. This limitation greatly increases detection time and poses an increased risk of infection. Here, we present a graphene field-effect transistor (GFET) based on the CRISPR/Cas system for detecting Mycobacterium tuberculosis. The CRISPR/Cas12a system has the ability to specifically recognize and cleave target DNA. By integrating the system onto the FET platform and utilizing its electrical amplification capability, we achieve rapid and sensitive detection without requiring sample pre-amplification, with a limit of detection (LoD) as low as 2.42 × 10-18 M. Cas12a-GFET devices can differentiate 30 positive cases from 56 serum samples within 5 minutes. These findings highlight its immense potential in future biological analysis and clinical diagnosis.

Cation Enrichment Effect Modulated Nafion/Graphene Field-Effect Transistor for Ultrasensitive RNA Detection

The graphene field-effect transistor (GFET) biosensor serves as a foundational platform for detecting biomolecules, offering high conductivity, label-free operation, and easy integration. These features have garnered significant attention in biomarker detection. However, the presence of free cations in solution often leads to electrostatic shielding of negatively charged biomolecules, reducing GFET detection sensitivity (LOD ≥ 1 fM). Additionally, the limited capacitance change in GFET restricts its use as a response signal. This study introduces a cation enrichment electric field modulation strategy (CEEFMS) to enhance capacitance and Dirac voltage response during detection. The cation-enriched rough Nafion/graphene FET (CENG-FET) achieves RNA detection at the aM level. Utilizing total capacitance change and Dirac voltage shift as response signals, the CENG-FET demonstrates a wide linear range from 1 aM to 1 pM. These findings advance dual-signal detection strategies, reducing accidental inaccuracies in biomolecular sensing and paving the way for further research.

Recent Advance in Single-Molecule Fluorescent Biosensors for Tumor Biomarker Detection

The construction of biosensors for specific, sensitive, and rapid detection of tumor biomarkers significantly contributes to biomedical research and early cancer diagnosis. However, conventional assays often involve large sample consumption and poor sensitivity, limiting their further application in real samples. In recent years, single-molecule biosensing has emerged as a robust tool for detecting and characterizing biomarkers due to its unique advantages including simplicity, low sample consumption, ultra-high sensitivity, and rapid assay time. This review summarizes the recent advances in the construction of single-molecule biosensors for the measurement of various tumor biomarkers, including DNAs, DNA modifications, RNAs, and enzymes. We give a comprehensive review about the working principles and practical applications of these single-molecule biosensors. Additionally, we discuss the challenges and limitations of current single-molecule biosensors, and highlight the future directions.

Synthesis, Modulation, and Application of Two-Dimensional TMD Heterostructures

Two-dimensional (2D) transition metal dichalcogenide (TMD) heterostructures have attracted a lot of attention due to their rich material diversity and stack geometry, precise controllability of structure and properties, and potential practical applications. These heterostructures not only overcome the inherent limitations of individual materials but also enable the realization of new properties through appropriate combinations, establishing a platform to explore new physical and chemical properties at micro-nano-pico scales. In this review, we systematically summarize the latest research progress in the synthesis, modulation, and application of 2D TMD heterostructures. We first introduce the latest techniques for fabricating 2D TMD heterostructures, examining the rationale, mechanisms, advantages, and disadvantages of each strategy. Furthermore, we emphasize the importance of characteristic modulation in 2D TMD heterostructures and discuss some approaches to achieve novel functionalities. Then, we summarize the representative applications of 2D TMD heterostructures. Finally, we highlight the challenges and future perspectives in the synthesis and device fabrication of 2D TMD heterostructures and provide some feasible solutions.

Sensitivity-Enhancing Strategies of Graphene Field-Effect Transistor Biosensors for Biomarker Detection

The ultrasensitive recognition of biomarkers plays a crucial role in the precise diagnosis of diseases. Graphene-based field-effect transistors (GFET) are considered the most promising devices among the next generation of biosensors. GFET biosensors possess distinct advantages, including label-free, ease of integration and operation, and the ability to directly detect biomarkers in liquid environments. This review summarized recent advances in GFET biosensors for biomarker detection, with a focus on interface functionalization. Various sensitivity-enhancing strategies have been overviewed for GFET biosensors, from the perspective of optimizing graphene synthesis and transfer methods, refinement of surface functionalization strategies for the channel layer and gate electrode, design of biorecognition elements and reduction of nonspecific adsorption. Further, this review extensively explores GFET biosensors functionalized with antibodies, aptamers, and enzymes. It delves into sensitivity-enhancing strategies employed in the detection of biomarkers for various diseases (such as cancer, cardiovascular diseases, neurodegenerative disorders, infectious viruses, etc.) along with their application in integrated microfluidic systems. Finally, the issues and challenges in strategies for the modulation of biosensing interfaces are faced by GFET biosensors in detecting biomarkers.

Interplay of graphene-DNA interactions: Unveiling sensing potential of graphene materials

Graphene-based materials and DNA probes/nanostructures have emerged as building blocks for constructing powerful biosensors. Graphene-based materials possess exceptional properties, including two-dimensional atomically flat basal planes for biomolecule binding. DNA probes serve as excellent selective probes, exhibiting specific recognition capabilities toward diverse target analytes. Meanwhile, DNA nanostructures function as placement scaffolds, enabling the precise organization of molecular species at nanoscale and the positioning of complex biomolecular assays. The interplay of DNA probes/nanostructures and graphene-based materials has fostered the creation of intricate hybrid materials with user-defined architectures. This advancement has resulted in significant progress in developing novel biosensors for detecting DNA, RNA, small molecules, and proteins, as well as for DNA sequencing. Consequently, a profound understanding of the interactions between DNA and graphene-based materials is key to developing these biological devices. In this review, we systematically discussed the current comprehension of the interaction between DNA probes and graphene-based materials, and elucidated the latest advancements in DNA probe-graphene-based biosensors. Additionally, we concisely summarized recent research endeavors involving the deposition of DNA nanostructures on graphene-based materials and explored imminent biosensing applications by seamlessly integrating DNA nanostructures with graphene-based materials. Finally, we delineated the primary challenges and provided prospective insights into this rapidly developing field. We envision that this review will aid researchers in understanding the interactions between DNA and graphene-based materials, gaining deeper insight into the biosensing mechanisms of DNA-graphene-based biosensors, and designing novel biosensors for desired applications.

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.

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.

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.

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.

Nucleotide detection mechanism and comparison based on low-dimensional materials: A review

The recent pandemic has led to the fabrication of new nucleic acid sensors that can detect infinitesimal limits immediately and effectively. Therefore, various techniques have been demonstrated using low-dimensional materials that exhibit ultrahigh detection and accuracy. Numerous detection approaches have been reported, and new methods for impulse sensing are being explored. All ongoing research converges at one unique point, that is, an impetus: the enhanced limit of detection of sensors. There are several reviews on the detection of viruses and other proteins related to disease control point of care; however, to the best of our knowledge, none summarizes the various nucleotide sensors and describes their limits of detection and mechanisms. To understand the far-reaching impact of this discipline, we briefly discussed conventional and nanomaterial-based sensors, and then proposed the feature prospects of these devices. Two types of sensing mechanisms were further divided into their sub-branches: polymerase chain reaction and photospectrometric-based sensors. The nanomaterial-based sensor was further subdivided into optical and electrical sensors. The optical sensors included fluorescence (FL), surface plasmon resonance (SPR), colorimetric, and surface-enhanced Raman scattering (SERS), while electrical sensors included electrochemical luminescence (ECL), microfluidic chip, and field-effect transistor (FET). A synopsis of sensing materials, mechanisms, detection limits, and ranges has been provided. The sensing mechanism and materials used were discussed for each category in terms of length, collectively forming a fusing platform to highlight the ultrahigh detection technique of nucleotide sensors. We discussed potential trends in improving the fabrication of nucleotide nanosensors based on low-dimensional materials. In this area, particular aspects, including sensitivity, detection mechanism, stability, and challenges, were addressed. The optimization of the sensing performance and selection of the best sensor were concluded. Recent trends in the atomic-scale simulation of the development of Deoxyribonucleic acid (DNA) sensors using 2D materials were highlighted. A critical overview of the challenges and opportunities of deoxyribonucleic acid sensors was explored, and progress made in deoxyribonucleic acid detection over the past decade with a family of deoxyribonucleic acid sensors was described. Areas in which further research is needed were included in the future scope.

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.

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.

Laser-Induced Graphene-Functionalized Field-Effect Transistor-Based Biosensing: A Potent Candidate for COVID-19 Detection

Speedy and on-time detection of coronavirus disease 2019 (COVID-19) is of high importance to control the pandemic effectively and stop its disastrous consequences. A widely available, reliable, label-free, and rapid test that can recognize tiny amounts of specific biomarkers might be the solution. Nanobiosensors are one of the most attractive candidates for this purpose. Integration of graphene with biosensing devices shifts the performance of these systems to an incomparable level. Between the various arrangements using this wonder material, field-effect transistors (FETs) display a precise detection even in complex samples. The emergence of pioneering biosensors for detecting a wide range of diseases especially COVID-19 created the incentive to prepare a review of the recent graphene-FET biosensing platforms. However, the graphene fabrication and transfer to the surface of the device is an imperative factor for researchers to take into account. Therefore, we also reviewed the common methods of manufacturing graphene for biosensing applications and discuss their advantages and disadvantages. One of the most recent synthesizing techniques - laser-induced graphene (LIG) - is attracting attention owing to its extraordinary benefits which are thoroughly explained in this article. Finally, a conclusion highlighting the current challenges is presented.

Graphene oxide-graphene Van der Waals heterostructure transistor biosensor for SARS-CoV-2 protein detection

The current outbreaking of the coronavirus SARS-CoV-2 pandemic threatens global health and has caused serious concern. Currently there is no specific drug against SARS-CoV-2, therefore, a fast and accurate diagnosis method is an urgent need for the diagnosis, timely treatment and infection control of COVID-19 pandemic. In this work, we developed a field effect transistor (FET) biosensor based on graphene oxide-graphene (GO/Gr) van der Waals heterostructure for selective and ultrasensitive SARS-CoV-2 proteins detection. The GO/Gr van der Waals heterostructure was in-situ formed in the microfluidic channel through π-π stacking. The developed biosensor is capable of SARS-CoV-2 proteins detection within 20 min in the large dynamic range from 10 fg/mL to 100 pg/mL with the limit of detection of as low as ∼8 fg/mL, which shows ∼3 × sensitivity enhancement compared with Gr-FET biosensor. The performance enhancement mechanism was studied based on the transistor-based biosensing theory and experimental results, which is mainly attributed to the enhanced SARS-CoV-2 capture antibody immobilization density due to the introduction of the GO layer on the graphene surface. The spiked SARS-CoV-2 protein samples in throat swab buffer solution were tested to confirm the practical application of the biosensor for SARS-CoV-2 proteins detection. The results indicated that the developed GO/Gr van der Waals heterostructure FET biosensor has strong selectivity and high sensitivity, providing a potential method for SARS-CoV-2 fast and accurate detection.

Poly-l-Lysine-Modified Graphene Field-Effect Transistor Biosensors for Ultrasensitive Breast Cancer miRNAs and SARS-CoV-2 RNA Detection

(Mi)RNAs are important biomarkers for cancers diagnosis and pandemic diseases, which require fast, ultrasensitive, and economical detection strategies to quantitatively detect exact (mi)RNAs expression levels. The novel coronavirus disease (SARS-CoV-2) has been breaking out globally, and RNA detection is the most effective way to identify the SARS-CoV-2 virus. Here, we developed an ultrasensitive poly-l-lysine (PLL)-functionalized graphene field-effect transistor (PGFET) biosensor for breast cancer miRNAs and viral RNA detection. PLL is functionalized on the channel surface of GFET to immobilize DNA probes by the electrostatic force. The results show that PGFET biosensors can achieve a (mi)RNA detection range of five orders with a detection limit of 1 fM and an entire detection time within 20 min using 2 μL of human serum and throat swab samples, which exhibits more than 113% enhancement in terms of sensitivity compared to that of GFET biosensors. The performance enhancement mechanisms of PGFET biosensors were comprehensively studied based on an electrical biosensor theoretical model and experimental results. In addition, the PGFET biosensor was applied for the breast cancer miRNA detection in actual serum samples and SARS-CoV-2 RNA detection in throat swab samples, providing a promising approach for rapid cancer diagnosis and virus screening.

Chemical Information in the L3 X-ray Absorption Spectra of Molybdenum Compounds by High-Energy-Resolution Detection and Density Functional Theory

X-ray spectroscopy using high-energy-resolution fluorescence detection (HERFD) has critically increased the information content in X-ray spectra. We extend this technique to the tender X-ray range and present a study at the L₃-edge of molybdenum. We show how information on the oxidation state, phase composition, and local environment in molybdenum-based compounds can be obtained by analyzing the HERFD L₃ X-ray absorption near-edge structure (XANES). We demonstrate that the chemical shift of the L₃-edge HERFD spectra follows a parabolic dependence on the oxidation state and show that a qualitative analysis of high-resolution spectra can help to estimate parameters such as distortion of a ligand environment and radial order of atoms around the absorber. In certain cases, the spectra allow disentangling the contributions from bond lengths and angles to the distortion of the ligand polyhedron. Comparison of the high-resolution spectra with theoretical simulations shows that the single-electron approximation is able to reproduce the spectral shape. The results of this work may be useful in every branch of physics, inorganic and organometallic chemistry, catalysis, materials science, biochemistry, and mineralogy where observed changes in performance or chemical properties of Mo-based compounds, accompanied by small changes in spectral shape, are to be related to the details of electronic structure and local atomic environment.

A sensitive platform for DNA detection based on organic electrochemical transistor and nucleic acid self-assembly signal amplification

Highly sensitive detection of DNA is of great importance for the detection of genetic damage and errors for the diagnosis of many diseases. Traditional highly sensitive organic electrochemical transistor (OECT)-based methods mainly rely on good conductivity materials, which may be limited by complex synthesis and modification steps. In this work, DNA biosensor based on OECT and hybridization chain reaction (HCR) signal amplification was demonstrated for the first time. Au nanoparticles were electrochemically deposited on the Au gate electrode to increase the surface area. Then, the HCR products, long negatively charged double-stranded DNA, were connected to the target by hybridization, which can increase the effective gate voltage offset of OECT. This sensor exhibited high sensitivity and even 0.1 pM target DNA could be directly detected with a significant voltage shift. In addition, it could discriminate target DNA from the mismatched DNA with good selectivity. This proposed method based on HCR in DNA detection exhibited an efficient amplification performance on OECT, which provided new opportunities for highly sensitive and selective detection of DNA.

A new method has been developed for DNA detection by integrating hybridization chain reaction signal amplification with organic electrochemical transistor device for the first time.

[ARTICLE WITHDRAWN] Semiconducting Polymer Dot-Based Ratiometric Fluorescence Nanoprobe for DNA Detection

THIS ARTICLE WAS WITHDRAWN BY THE PUBLISHER IN MAY 2021

Aluminum Microcomb Electrodes on Silicon Wafer for Detecting Val66Met Polymorphism in Brain-Derived Neurotrophic Factor

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) dysregulation is widely related with various psychiatric and neurological disorders, including schizophrenia, depression, Rett syndrome, and addiction, and the available evidence suggests that BDNF is also highly correlated with Parkinson's and Alzheimer's diseases.

METHODS

The BDNF target sequence was detected on a capture probe attached on aluminum microcomb electrodes on the silicon wafer surface. A capture-target-reporter sandwich-type assay was performed to enhance the detection of the BDNF target.

RESULTS

The limit of detection was noticed to be 100 aM. Input of a reporter sequence at concentrations >10 aM improved the detection of the target sequence by enhancing changes in the generated currents. Control experiments with noncomplementary and single- and triple-mismatches of target and reporter sequences did not elicit changes in current levels, indicating the selective detection of the BDNF gene sequence.

CONCLUSION

The above detection strategy will be useful for the detection and quantification of BDNF, thereby aiding in the provision of suitable treatments for BDNF-related disorders.

Graphene for Biosensing Applications in Point-of-Care Testing

Graphene and graphene-related materials (GRMs) exhibit a unique combination of electronic, optical, and electrochemical properties, which make them ideally suitable for ultrasensitive and selective point-of-care testing (POCT) devices. POCT device-based applications in diagnostics require test results to be readily accessible anywhere to produce results within a short analysis timeframe. This review article provides a summary of methods and latest developments in the field of graphene and GRM-based biosensing in POCT and an overview of the main applications of the latter in nucleic acids and enzymatic biosensing, cell detection, and immunosensing. For each application, we discuss scientific and technological advances along with the remaining challenges, outlining future directions for widespread use of this technology in biomedical applications.

Graphene field-effect transistors as bioanalytical sensors: design, operation and performance

Graphene field-effect transistors (GFETs) are emerging as bioanalytical sensors, in which their responsive electrical conductance is used to perform quantitative analyses of biologically-relevant molecules such as DNA, proteins, ions and small molecules. This review provides a detailed evaluation of reported approaches in the design, operation and performance assessment of GFET biosensors. We first dissect key design elements of these devices, along with most common approaches for their fabrication. We compare possible modes of operation of GFETs as sensors, including transfer curves, output curves and time series as well as their integration in real-time or a posteriori protocols. Finally, we review performance metrics reported for the detection and quantification of bioanalytes, and discuss limitations and best practices to optimize the use of GFETs as bioanalytical sensors.

Cytochrome c light-up graphene oxide nanosensor for the targeted self-monitoring of mitochondria-mediated tumor cell death

Targeting mitochondria-mediated apoptosis has emerged as a promising strategy for tumor therapy. However, technologies used to treat tumors that enable the direct visualization of mitochondria-mediated apoptosis in living cells have not been developed to date. Cytochrome c (Cyt c) translocation from mitochondria is a central mediating event in cell apoptosis. In this study, we developed a multifunctional nanosensor that can monitor the real-time translocation of Cyt c from mitochondria in living cells to evaluate the antitumor effect of dihydroartemisinin (DHA). A fluorophore-tagged DNA aptamer is loaded on a graphene oxide (GO)-based nanovehicle, and the cytosolic release of Cyt c causes the dissociation of the aptamer from the GO nanovehicle and triggers the emission of a red fluorescence signal. Furthermore, DHA linked with a coumarin derivative is loaded on GO as a mitochondria-targeting ligand to improve its antitumor activity. This DHA prodrug also emits a green fluorescence signal when delivered to mitochondria. This nanosensor provides a convenient mechanism to monitor mitochondrial targeting by drugs and mitochondria-induced therapeutic efficacy, which may be possible to diagnose the drug efficacy to optimize the treatment for patients with cancer.

Review of fabrication methods of large-area transparent graphene electrodes for industry

Graphene is a two-dimensional material showing excellent properties for utilization in transparent electrodes; it has low sheet resistance, high optical transmission and is flexible. Whereas the most common transparent electrode material, tin-doped indium-oxide (ITO) is brittle, less transparent and expensive, which limit its compatibility in flexible electronics as well as in low-cost devices. Here we review two large-area fabrication methods for graphene based transparent electrodes for industry: liquid exfoliation and low-pressure chemical vapor deposition (CVD). We discuss the basic methodologies behind the technologies with an emphasis on optical and electrical properties of recent results. State-of-the-art methods for liquid exfoliation have as a figure of merit an electrical and optical conductivity ratio of 43.5, slightly over the minimum required for industry of 35, while CVD reaches as high as 419.