Discrimination of single-point mutations in unamplified genomic DNA via Cas9 immobilized on a graphene field-effect transistor

Recent Advances in Xenes Based FET for Biosensing Applications

In recent years, monoelemental 2D materials (Xenes) such as graphene, graphdiyne, silicene, phosphorene, and tellurene, have gained significant traction in biosensing applications. Owing to their ultra-thin layered structure, exceptionally high specific surface area, unique surface electronic properties, excellent mechanical strength, flexibility, and other distinctive features, Xenes are recognized for their potential as materials with low detection limits, high speed, and exceptional flexibility in biosensing applications. In this review, the unique properties of Xenes, their synthesis, and recent theoretical and experimental advances in applications related to biosensing, including DNA/RNA biosensors, protein biosensors, small molecule biosensors, cell, and ion biosensors are comprehensively summarized. Finally, the challenges and prospects of this emerging field are discussed.

2D Materials-Based Field-Effect Transistor Biosensors for Healthcare

The need for accurate point-of-care (POC) tools, driven by increasing demands for precise medical diagnostics and monitoring, has accelerated the evolution of biosensor technology. Integrable 2D materials-based field-effect transistor (2D FET) biosensors offer label-free, rapid, and ultrasensitive detection, aligning perfectly with current biosensor trends. Given these advancements, this review focuses on the progress, challenges, and future prospects in the field of 2D FET biosensors. The distinctive physical properties of 2D materials and recent achievements in scalable synthesis are highlighted that significantly improve the manufacturing process and performance of FET biosensors. Additionally, the advancements of 2D FET biosensors are investigated in fatal disease diagnosis and screening, chronic disease management, and environmental hazards monitoring, as well as their integration in flexible electronics. Their promising capabilities shown in laboratory trials accelerate the development of prototype products, while the challenges are acknowledged, related to sensitivity, stability, and scalability that continue to impede the widespread adoption and commercialization of 2D FET biosensors. Finally, current strategies are discussed to overcome these challenges and envision future implications of 2D FET biosensors, such as their potential as smart and sustainable POC biosensors, thereby advancing human healthcare.

Detection of HPV 16 and 18 L1 genes by a nucleic acid amplification-free electrochemical biosensor powered by CRISPR/Cas9

Cervical cancer, closely linked to Human Papillomavirus (HPV) infection, remains a significant health threat for women worldwide. Conventional HPV detection methods, such as reverse transcription polymerase chain reaction (RT-PCR), rely on nucleic acid amplification (NAA), which can be costly and time-consuming. This study introduces an NAA-free electrochemical Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based biosensor designed to detect HPV 16 and HPV 18 L1 genes simultaneously. The system utilizes a Cas9-single guided RNA complex to initiate a selective cleavage reaction, releasing Methylene blue or Ferrocene-labeled fragments correlate to L1 gene concentrations. These fragments then interact with modified gold electrodes immobilized with a complementary probe, allowing precise electrochemical signal measurement during hybridization. The biosensor offers a wide detection range from 1 fM to 10 nM, with detection limits as low as 0.4 fM for HPV 16 L1 and 0.51 fM for HPV 18 L1, providing a sensitive and efficient solution for L1 gene detection. Additionally, its specificity and sensitivity closely match RT-PCR results in clinical testing, highlighting its potential for molecular diagnostics and point-of-care applications.

Nanotechnology-leveraged CRISPR/Cas systems: icebreaking in trace cancer-related nucleic acids biosensing

As promising noninvasive biomarkers, nucleic acids provide great potential to innovate cancer early detection methods and promote subsequent diagnosis to improve the survival rates of patient. Accurate, straightforward and sensitive detection of such nucleic acid-based cancer biomarkers in complex biological samples holds significant clinical importance. However, the low abundance creates huge challenges for their routine detection. As the next-generation diagnostic tool, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein (Cas) with their high programmability, sensitivity, fidelity, single-base resolution, and precise nucleic acid positioning capabilities are extremely attractive for trace nucleic acid-based cancer biomarkers (NABCBs), permitting rapid, ultra-sensitive and specific detection. More importantly, by combing with nanotechnology, it can solve the long-lasting problems of poor sensitivity, accuracy and simplicity, as well as to achieve integrated miniaturization and portable point-of-care testing (POCT) detection. However, existing literature lacks specific emphasis on this topic. Thus, we intend to propose a timely one for the readers. This review will bridge this gap by providing insights for CRISPR/Cas-based nano-biosensing development and highlighting the current state-of-art, challenges, and prospects. We expect that it can provide better understanding and valuable insights for trace NABCBs detection, thereby facilitating advancements in early cancer screening/detection/diagnostics and win practical applications in the foreseeable future.

A portable and cost-effective system for electronic nucleic acid mass measurement

This paper presents a low-cost, portable sensing platform for rapid DNA mass measurement, addressing a critical need in life science research. The platform features a novel interdigital open-gate junction field-effect transistor (ID-OGJFET) with a large sensing area that converts negatively charged DNA mass into an electrical current. The system enables DNA mass detection in under ten seconds with a resolution of less than 1 µA, demonstrating sensitivity across a range from 0.48 ng to 29.5 ng, achieving a Limit of Detection as low as 1.18-1.25 ng/µL. A custom-designed electronic reader and fluidic sample holder facilitate efficient operation. Simulation studies using molecular dynamics and finite element methods provide further insights into the sensor's DNA detection mechanism. This highly sensitive system is significantly more cost-effective than commercially available semiconductor characterization alternatives. The device's high performance and affordability make it a valuable tool for molecular biology applications, and it holds potential for advancing FET-based sensing instrumentation and measurement research.

CRISPR/RNA Aptamer System Activated by an AND Logic Gate for Biomarker-Driven Theranostics

The development of an engineered RNA device capable of detecting multiple biomarkers to evaluate pathological states and autonomously implement responsive therapies is urgently needed. Here, we report InCasApt, an integrated nano CRISPR Cas13a/RNA aptamer theranostic platform capable of achieving both biomarker detection and biomarker-driven therapy. Within this system, a Cas13a/crRNA complex, a hairpin reporter (HR), a dinitroaniline caged Ce6 photosensitizer (Ce6-DN), and a DN-binding RNA aptamer precursor (DNBApt) are coloaded onto dendritic mesoporous silicon nanoparticles (DMSN) in a controlled manner. While InCasApt remains inert in normal cells, its programmable theranostic capabilities are activated in tumor cells that have elevated expression of carcinogenic miRNA-155 and miRNA-21. These miRNAs act as an AND logic gate, generating fluorescence for disease condition evaluation and ROS for photodynamic therapy. This process also upregulates antioncogene BRG1 and suppresses tumor migration by inhibiting the function of miRNA-155 and miRNA-21. These effects underscore the versatility of InCasApt as an miRNA-targeting strategy for bridging the gap between diagnosis and therapy.

CRISPR-Cas technology in forensic investigations: Principles, applications, and ethical considerations

CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins) systems are adaptive immune systems originally present in bacteria, where they are essential to protect against external genetic elements, including viruses and plasmids. Taking advantage of this system, CRISPR-Cas-based technologies have emerged as incredible tools for precise genome editing, thus significantly advancing several research fields. Forensic sciences represent a multidisciplinary field that explores scientific methods to investigate and resolve legal issues, particularly criminal investigations and subject identification. Consequently, it plays a critical role in the justice system, providing scientific evidence to support judicial investigations. Although less explored, CRISPR-Cas-based methodologies demonstrate strong potential in the field of forensic sciences due to their high accuracy and sensitivity, including DNA profiling and identification, interpretation of crime scene investigations, detection of food contamination or fraud, and other aspects related to environmental forensics. However, using CRISPR-Cas-based methodologies in human samples raises several ethical issues and concerns regarding the potential misuse of individual genetic information. In this manuscript, we provide an overview of potential applications of CRISPR-Cas-based methodologies in several areas of forensic sciences and discuss the legal implications that challenge their routine implementation in this research field.

Multifunctional Integrated Biosensors Based on Two-Dimensional Field-Effect Transistors

In recent years, field-effect transistor (FET) sensing technology has attracted significant attention owing to its noninvasive, label-free, real-time, and user-friendly detection capabilities. Owing to the large specific surface area, high flexibility, and excellent conductivity of two-dimensional (2D) materials, FET biosensors based on 2D materials have demonstrated unique potential in biomarker analysis and healthcare applications, driving continuous innovation and transformation in the field. Here, we review recent trends in the development of 2D FET biosensors based on key performance metrics and main characteristics, and we also discuss structural designs and modification strategies for biosensing devices utilizing graphene, transition metal dichalcogenides, black phosphorus, and other 2D materials to enhance key performance metrics. Finally, we offer insights into future directions for biosensor advancements, discuss potential improvements, and present new recommendations for practical clinical applications.

One Stone Two Birds: Anomalously Enhancing the Cross-Plane and In-Plane Heat Transfer in 2D/3D Heterostructures by Defects Engineering

This study addresses a crucial challenge in two-dimensional (2D) material-based electronic devices-inefficient heat dissipation across the van der Waals (vdW) interface connecting the 2D material to its three-dimensional (3D) substrate. The objective is to enhance the interfacial thermal conductance (ITC) of 2D/3D heterostructures without compromising the intrinsic thermal conductivities (κ) of 2D materials. Using 2D-MoS2/3D-GaN as an example, a novel strategy to enhance both the ITC across 2D/3D interface and κ of 2D material is proposed by introducing a controlled concentration (ρ) of vacancy defects to substrate's bottom surface. Molecular dynamics simulations demonstrate a notable 2.1-fold higher ITC of MoS2/GaN at ρ = 4% compared to the no-defective counterpart, along with an impressive 56% enhancement in κ of MoS2 compared to the conventional upper surface modification approaches. Phonon dynamics analysis attributes the ITC enhancement to increased phonon coupling between MoS2 and GaN, resulting from polarization conversion and hybridization of phonons at the defective surface. Spectral energy density analysis affirms that the improved κ of MoS2 directly results from the proposed strategy, effectively reducing phonon scattering at the interface. This work provides an effective approach for enhancing heat transfer in 2D/3D vdW heterostructures, promisingly advancing electronics' heat dissipation.

Overcoming Debye screening effect in field-effect transistors for enhanced biomarker detection sensitivity

Field-effect transistor (FET)-based biosensors not only enable label-free detection by measuring the intrinsic charges of biomolecules, but also offer advantages such as high sensitivity, rapid response, and ease of integration. This enables them to play a significant role in disease diagnosis, point-of-care detection, and drug screening, among other applications. However, when FET sensors detect biomolecules in physiological solutions (such as whole blood, serum, etc.), the charged molecules will be surrounded by oppositely charged ions in the solution. This causes the effective charge carried by the biomolecules to be shielded, thereby significantly weakening their ability to induce charge rearrangement at the sensing interface. Such shielding hinders the change of carriers inside the sensing material, reduces the variation of current between the source and drain electrodes of the FET, and seriously limits the sensitivity and reliability of the device. In this article, we summarize the research progress in overcoming the Debye screening effect in FET-based biosensors over the past decade. Here, we first elucidate the working principles of FET sensors for detecting biomarkers and the mechanism of the Debye screening. Subsequently, we emphasize optimization strategies to overcome the Debye screening effect. Finally, we summarize and provide an outlook on the research on FET biosensors in overcoming the Debye screening effect, hoping to help the development of FET electronic devices with high sensitivity, specificity, and stability. This work is expected to provide new ideas for next-generation biosensing technology.

A Propidium Monoazide-Assisted Digital CRISPR/Cas12a Assay for Selective Detection of Live Bacteria in Sample

Escherichia coli O157:H7 (E. coli O157:H7) is a prominent pathogenic bacterium that poses serious risks to food safety and public health. Rapid and accurate detection of live E. coli O157:H7 is of great importance in food quality monitoring and clinical diagnosis. Here, we report a propidium monoazide-assisted nonamplification digital CRISPR/Cas12a assay for sensitive and rapid detection of live E. coli O157:H7. The incorporation of propidium monoazide into the method enables the selective detection of live bacteria by eliminating 98% of interference from the dead bacterial nucleic acid. Implemented on microfluidic digital chips, this method can achieve absolute quantification of nonamplified nucleic acid. The entire detection process of live bacteria can be completed within 120 min without the need for establishing a standard curve, and the sensitivity of the method reaches 1.2 × 103 CFU/mL. The method was validated using various samples, yielding results consistent with the plate counting method (Pearson's r = 0.9490). Consequently, this method holds significant potential for applications in fields requiring live bacterial detection.

Localization and discrimination of GG mismatch in duplex DNA by synthetic ligand-enhanced protein nanopore analysis

Mismatched base pairs in DNA are the basis of single-nucleotide polymorphism, one of the major issues in genetic diseases. However, the changes of physical and chemical properties of DNA caused by single-site mismatches are often influenced by the sequence and the structural flexibility of the whole duplex, resulting in a challenge of direct detection of the types and location of mismatches sensitively. In this work, we proposed a synthetic ligand-enhanced protein nanopore analysis of GG mismatch on DNA fragment, inspired by in silico investigation of the specific binding of naphthyridine dimer (ND) on GG mismatch. We demonstrated that both the importing and unzipping processes of the ligand-bound DNA duplex can be efficiently slowed down in α-hemolysin nanopore. This ligand-binding induced slow-down effect of DNA in nanopore is also sensitive to the relative location of the mismatch on DNA duplex. Especially, the GG mismatch close to the end of a DNA fragment, which is hard to be detected by either routine nanopore analysis or tedious nanopore sequencing, can be well differentiated by our ND-enhanced nanopore experiment. These findings provide a promising strategy to localize and discriminate base mismatches in duplex form directly at the single-molecule level.

CRISPR-Cas Systems Associated with Electrolyte-Gated Graphene-Based Transistors: How They Work and How to Combine Them

In this review, recent advances in the combination of CRISPR-Cas systems with graphene-based electrolyte-gated transistors are discussed in detail. In the first part, the functioning of CRISPR-Cas systems is briefly explained, as well as the most common ways to convert their molecular activity into measurable signals. Other than optical means, conventional electrochemical transducers are also developed. However, it seems that the incorporation of CRISPR/Cas systems into transistor devices could be extremely powerful, as the former provides molecular amplification, while the latter provides electrical amplification; combined, the two could help to advance in terms of sensitivity and compete with conventional PCR assays. Today, organic transistors suffer from poor stability in biological media, whereas graphene materials perform better by being extremely sensitive to their chemical environment and being stable. The need for fast and inexpensive sensors to detect viral RNA arose on the occasion of the COVID-19 crisis, but many other RNA viruses are of interest, such as dengue, hepatitis C, hepatitis E, West Nile fever, Ebola, and polio, for which detection means are needed.

CRISPR for companion diagnostics in low-resource settings

New point-of-care tests (POCTs), which are especially useful in low-resource settings, are needed to expand screening capacity for diseases that cause significant mortality: tuberculosis, multiple cancers, and emerging infectious diseases. Recently, clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostic (CRISPR-Dx) assays have emerged as powerful and versatile alternatives to traditional nucleic acid tests, revealing a strong potential to meet this need for new POCTs. In this review, we discuss CRISPR-Dx assay techniques that have been or could be applied to develop POCTs, including techniques for sample processing, target amplification, multiplex assay design, and signal readout. This review also describes current and potential applications for POCTs in disease diagnosis and includes future opportunities and challenges for such tests. These tests need to advance beyond initial assay development efforts to broadly meet criteria for use in low-resource settings.

CRISPR-enabled point-of-care genotyping for APOL1 genetic risk assessment

Detecting genetic variants enables risk factor identification, disease screening, and initiation of preventative therapeutics. However, current methods, relying on hybridization or sequencing, are unsuitable for point-of-care settings. In contrast, CRISPR-based-diagnostics offer high sensitivity and specificity for point-of-care applications. While these methods have predominantly been used for pathogen sensing, their utilization for genotyping is limited. Here, we report a multiplexed CRISPR-based genotyping assay using LwaCas13a, PsmCas13b, and LbaCas12a, enabling the simultaneous detection of six genotypes. We applied this assay to identify genetic variants in the APOL1 gene prevalent among African Americans, which are associated with an 8-30-fold increase in the risk of developing kidney disease. Machine learning facilitated robust analysis across a multicenter clinical cohort of more than 100 patients, accurately identifying their genotypes. In addition, we optimized the readout using a multi-analyte lateral-flow assay demonstrating the ability for simplified genotype determination of clinical samples. Our CRISPR-based genotyping assay enables cost-effective point-of-care genetic variant detection due to its simplicity, versatility, and fast readout.

Programmable and ultra-efficient Argonaute protein-mediated nucleic acid tests: A review

With the attributes of high sensitivity, single-base resolution, multiplex detection capability, and programmability upon nucleic acid recognition, Argonaute (Ago)-based biosensing assays are increasingly recognized as one of the most promising tools for precise identification and quantification of target analytes. Employed as highly specific sequence recognition elements of these robust diagnostic methods, Agos are revolutionizing how nucleic acid targets are detected. A systematic and comprehensive summary of this emerging and rapid-advancing technology is necessary to give play to the potential of Ago-based biosensing assays. The structure and function of Agos were briefly overviewed at the beginning of the work, followed by a review of the recent advancements in employing Agos sensing for detecting various targets with a comprehensive analysis such as viruses, tumor biomarkers, pathogens, mycoplasma, and parasite. The significance and benefits of these platforms were then deliberated. In addition, the authors shared subjective viewpoints on the existing challenges and offered relevant guidance for the future progress of Agos assays. Finally, the future research outlook regarding Ago-based sensing in this field was also outlined. As such, this review is expected to offer valuable information and fresh perspectives for a broader group of researchers.

CRISPR-Cas Systems: Programmable Nuclease Revolutionizing the Molecular Diagnosis

CRISPR-Cas system has evolved as a highly preferred genetic engineering tool to perform target gene manipulation via alteration of the guide RNA (gRNA) sequence. The ability to recognize and cleave a specific target with high precision has led to its applicability in multiple frontiers pertaining to human health and medicine. From basic research focused on understanding the molecular basis of disease to translational approach leading to early and precise disease diagnosis as well as developing effective therapeutics, the CRISPR-Cas system has proved to be a quite versatile tool. The coupling of CRISPR-Cas mediated cleavage with isothermal amplification (ISA) of target DNA, followed by a read-out using fluorescent or colorimetric reporters appears quite promising in providing a solution to the urgent need for nucleic acid-based point-of-care diagnostic. Hence, it has been recognized as a highly sophisticated molecular diagnostic tool for the detection of disease-specific biomarkers not limited to nucleic acids-based detection but also of non-nucleic acid targets such as proteins, exosomes, and other small molecules. In this review, we have presented salient features and principles of class 2 type II, V, and VI CRISPR-Cas systems represented by Cas9, Cas12, and Cas13 endonucleases which are frequently used in molecular diagnosis. The article then highlights different medical diagnostic applications of CRISPR-Cas systems focusing on the diagnosis of SARS-CoV-2, Dengue, Mycobacterium tuberculosis, and Listeria monocytogenes. Lastly, we discuss existing obstacles and potential future pathways concerning this subject in a concise manner.

Navigating the CRISPR/Cas Landscape for Enhanced Diagnosis and Treatment of Wilson's Disease

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) system continues to evolve, thereby enabling more precise detection and repair of mutagenesis. The development of CRISPR/Cas-based diagnosis holds promise for high-throughput, cost-effective, and portable nucleic acid screening and genetic disease diagnosis. In addition, advancements in transportation strategies such as adeno-associated virus (AAV), lentiviral vectors, nanoparticles, and virus-like vectors (VLPs) offer synergistic insights for gene therapeutics in vivo. Wilson's disease (WD), a copper metabolism disorder, is primarily caused by mutations in the ATPase copper transporting beta (ATP7B) gene. The condition is associated with the accumulation of copper in the body, leading to irreversible damage to various organs, including the liver, nervous system, kidneys, and eyes. However, the heterogeneous nature and individualized presentation of physical and neurological symptoms in WD patients pose significant challenges to accurate diagnosis. Furthermore, patients must consume copper-chelating medication throughout their lifetime. Herein, we provide a detailed description of WD and review the application of novel CRISPR-based strategies for its diagnosis and treatment, along with the challenges that need to be overcome.

Digitized Kinetic Analysis Enhances Genotyping Capacity of CRISPR-Based Biosensing

CRISPR/Cas systems have been widely employed for nucleic acid biosensing and have been further advanced for mutation detection by virtue of the sequence specificity of crRNA. However, existing CRISPR-based genotyping methods are limited by the mismatch tolerance of Cas effectors, necessitating a comprehensive screening of crRNAs to effectively distinguish between wild-type and point-mutated sequences. To circumvent the limitation of conventional CRISPR-based genotyping, here, we introduce Single-Molecule kinetic Analysis via a Real-Time digital CRISPR/Cas12a-assisted assay (SMART-dCRISPR). SMART-dCRISPR leverages the differential kinetics of the signal increase in CRISPR/Cas systems, which is modulated by the complementarity between crRNA and the target sequence. It employs single-molecule digital measurements to discern mutations based on kinetic profiles that could otherwise be obscured by variations in the target concentrations. We applied SMART-dCRISPR to genotype notable mutations in SARS-CoV-2, point mutation (K417N) and deletion (69/70DEL), successfully distinguishing wild-type, Omicron BA.1, and Omicron BA.2 SARS-CoV-2 strains from clinical nasopharyngeal/nasal swab samples. Additionally, we introduced a portable digital real-time sensing device to streamline SMART-dCRISPR and enhance its practicality for point-of-care settings. The combination of a rapid and sensitive isothermal CRISPR-based assay with single-molecule kinetic analysis in a portable format significantly enhances the versatility of CRISPR-based nucleic acid biosensing and genotyping.

Recent advances in enzyme-free and enzyme-mediated single-nucleotide variation assay in vitro

Single-nucleotide variants (SNVs) are the most common type variation of sequence alterations at a specific location in the genome, thus involving significant clinical and biological information. The assay of SNVs has engaged great awareness, because many genome-wide association studies demonstrated that SNVs are highly associated with serious human diseases. Moreover, the investigation of SNV expression levels in single cells are capable of visualizing genetic information and revealing the complexity and heterogeneity of single-nucleotide mutation-related diseases. Thus, developing SNV assay approaches in vitro, particularly in single cells, is becoming increasingly in demand. In this review, we summarized recent progress in the enzyme-free and enzyme-mediated strategies enabling SNV assay transition from sensing interface to the test tube and single cells, which will potentially delve deeper into the knowledge of SNV functions and disease associations, as well as discovering new pathways to diagnose and treat diseases based on individual genetic profiles. The leap of SNV assay achievements will motivate observation and measurement genetic variations in single cells, even within living organisms, delve into the knowledge of SNV functions and disease associations, as well as open up entirely new avenues in the diagnosis and treatment of diseases based on individual genetic profiles.

Sensing, Imaging, and Therapeutic Strategies Endowing by Conjugate Polymers for Precision Medicine

Conjugated polymers (CPs) have promising applications in biomedical fields, such as disease monitoring, real-time imaging diagnosis, and disease treatment. As a promising luminescent material with tunable emission, high brightness and excellent stability, CPs are widely used as fluorescent probes in biological detection and imaging. Rational molecular design and structural optimization have broadened absorption/emission range of CPs, which are more conductive for disease diagnosis and precision therapy. This review provides a comprehensive overview of recent advances in the application of CPs, aiming to elucidate their structural and functional relationships. The fluorescence properties of CPs and the mechanism of detection signal amplification are first discussed, followed by an elucidation of their emerging applications in biological detection. Subsequently, CPs-based imaging systems and therapeutic strategies are illustrated systematically. Finally, recent advancements in utilizing CPs as electroactive materials for bioelectronic devices are also investigated. Moreover, the challenges and outlooks of CPs for precision medicine are discussed. Through this systematic review, it is hoped to highlight the frontier progress of CPs and promote new breakthroughs in fundamental research and clinical transformation.

On-site detection and differentiation of African swine fever virus variants using an orthogonal CRISPR-Cas12b/Cas13a-based assay

The African swine fever virus (ASFV) and its variants have induced substantial economic losses in China, prompting a critical need for efficient detection methods. Several PCR-based methods have been developed to discriminate between wild-type ASFV and gene-deleted variants. However, the requirement for sophisticated equipment and skilled operators limits their use in field settings. Here, we developed a CRISPR-Cas12b/Cas13a-based detection assay that can identify ASFV variants with minimal equipment requirements and a short turnaround time. The assay utilizes the distinct DNA/RNA collateral cleavage preferences of Cas12b/Cas13a to detect two amplified targets from multiplex recombinase polymerase amplification (RPA) in a single tube, and the results can be visualized through fluorescent or lateral-flow readouts. When tested with clinical samples in field settings, our assay successfully detected all ASFV-positive samples in less than 60 min. This assay provides a rapid on-site surveillance tool for detecting ASFV and its emerging variants.

CRISPR/Cas9-mediated SERS/colorimetric dual-mode lateral flow platform combined with smartphone for rapid and sensitive detection of Staphylococcus aureus

Pathogenic bacteria infections pose a significant threat to global public health, making the development of rapid and reliable detection methods urgent. Here, we developed a surface-enhanced Raman scattering (SERS) and colorimetric dual-mode platform, termed smartphone-integrated CRISPR/Cas9-mediated lateral flow strip (SCC-LFS), and applied it to the ultrasensitive detection of Staphylococcus aureus (S. aureus). Strategically, functionalized silver-coated gold nanostar (AuNS@Ag) was prepared and used as the labeling material for LFS assay. In the presence of S. aureus, target gene-induced amplicons can be accurately recognized and unwound by the user-defined CRISPR/Cas9 system, forming intermediate bridges that bind many AuNS@Ag to the test line (T-line) of the strip. As a result, the T-line was colored and a recognizable SERS signal was obtained using a smartphone-integrated portable Raman spectrometer. This design not only maintains the simplicity of visual readout, but also integrates the quantitative capability of SERS, enabling the user to flexibly select the assay mode as needed. With this method, S. aureus down to 1 CFU/mL can be detected by both colorimetric and SERS modes, which is better than most existing methods. By incorporating a rapid extraction procedure, the entire assay can be completed in 45 min. The robustness and practicality of the method were further demonstrated by various real samples, indicating its considerable potential toward reliable screening of S. aureus.

Addressing Signal Drift and Screening for Detection of Biomarkers with Carbon Nanotube Transistors

Electrical biosensors, including transistor-based devices (i.e., BioFETs), have the potential to offer versatile biomarker detection in a simple, low-cost, scalable, and point-of-care manner. Semiconducting carbon nanotubes (CNTs) are among the most explored nanomaterial candidates for BioFETs due to their high electrical sensitivity and compatibility with diverse fabrication approaches. However, when operating in solutions at biologically relevant ionic strengths, CNT-based BioFETs suffer from debilitating levels of signal drift and charge screening, which are often unaccounted for or sidestepped (but not addressed) by testing in diluted solutions. In this work, we present an ultrasensitive CNT-based BioFET called the D4-TFT, an immunoassay with an electrical readout, which overcomes charge screening and drift-related limitations of BioFETs. In high ionic strength solution (1X PBS), the D4-TFT repeatedly and stably detects subfemtomolar biomarker concentrations in a point-of-care form factor by increasing the sensing distance in solution (Debye length) and mitigating signal drift effects. Debye length screening and biofouling effects are overcome using a poly(ethylene glycol)-like polymer brush interface (POEGMA) above the device into which antibodies are printed. Simultaneous testing of a control device having no antibodies printed over the CNT channel confirms successful detection of the target biomarker via an on-current shift caused by antibody sandwich formation. Drift in the target signal is mitigated by a combination of: (1) maximizing sensitivity by appropriate passivation alongside the polymer brush coating; (2) using a stable electrical testing configuration; and (3) enforcing a rigorous testing methodology that relies on infrequent DC sweeps rather than static or AC measurements. These improvements are realized in a relatively simple device using printed CNTs and antibodies for a low-cost, versatile platform for the ongoing pursuit of point-of-care BioFETs.

Ultraspecific One-Pot CRISPR-Based "Green-Yellow-Red" Multiplex Detection Strategy Integrated with Portable Cartridge for Point-of-Care Diagnosis

Versatile, informative, sensitive, and specific nucleic acid detection plays a crucial role in point-of-care pathogen testing, genotyping, and disease monitoring. In this study, we present a novel one-pot Cas12b-based method coupled with the "Green-Yellow-Red" strategy for multiplex detection. By integrating RT-LAMP amplification and Cas12b cleavage in a single tube, the entire detection process can be completed within 1 h. Our proposed method exhibits high specificity, enabling the discrimination of single-base mutations with detection sensitivity approaching single molecule levels. Additionally, the fluorescent results can be directly observed by the naked eye or automatically analyzed using our custom-designed software Result Analyzer. To realize point-of-care detection, we developed a portable cartridge capable of both heating and fluorescence excitation. In a clinical evaluation involving 20 potentially SARS-CoV-2-infected samples, our method achieved a 100% positive detection rate when compared to standard RT-PCR. Furthermore, the identification of SARS-CoV-2 variants using our method yielded results that were consistent with the sequencing results. Notably, our proposed method demonstrates excellent transferability, allowing for the simultaneous detection of various pathogens and the identification of mutations as low as 0.5% amidst a high background interference. These findings highlight the tremendous potential of our developed method for molecular diagnostics.

Chitosan modified graphene field-effect transistor biosensor for ultrasensitive procalcitonin detection

Sepsis is a systemic inflammatory response caused by a bacterial infection that often leading to tissue damage, organ failure and death. Procalcitonin (PCT), as a peptide precursor to hormones, is the main biomarker to identification of the sepsis. In this study, a chitosan modified graphene field transistor (CTS-GFET) was established and first time used for PCT ultra-sensitive detection. CTS was functionalized on the GFET channel surface to immobilized anti-PCT by glutaraldehyde. This biosensor exhibited the detection limit as low as 0.82 ag/mL in PBS, which exhibited 3 times enhancement compared with GFET biosensors. The enhancement mechanisms of CTS-GFET were studied by electrical theoretical model. In addition, the CTS-GFET biosensor was successfully applied to quantify the concentration of the PCT in human serum samples, indicating the potential use in clinical application.

Ultra-Fast Single-Nucleotide-Variation Detection Enabled by Argonaute-Mediated Transistor Platform

"Test-and-go" single-nucleotide variation (SNV) detection within several minutes remains challenging, especially in low-abundance samples, since existing methods face a trade-off between sensitivity and testing speed. Sensitive detection usually relies on complex and time-consuming nucleic acid amplification or sequencing. Here, a graphene field-effect transistor (GFET) platform mediated by Argonaute protein that enables rapid, sensitive, and specific SNV detection is developed. The Argonaute protein provides a nanoscale binding channel to preorganize the DNA probe, accelerating target binding and rapidly recognizing SNVs with single-nucleotide resolution in unamplified tumor-associated microRNA, circulating tumor DNA, virus RNA, and reverse transcribed cDNA when a mismatch occurs in the seed region. An integrated microchip simultaneously detects multiple SNVs in agreement with sequencing results within 5 min, achieving the fastest SNV detection in a "test-and-go" manner without the requirement of nucleic acid extraction, reverse transcription, and amplification.

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.

High-Performance Photodetectors Based on Semiconducting Graphene Nanoribbons

The inherent zero-band gap nature of graphene and its fast photocarrier recombination rate result in poor optical gain and responsivity when graphene is used as the light absorption medium in photodetectors. Here, semiconducting graphene nanoribbons with a direct bandgap of 1.8 eV are synthesized and employed to construct a vertical heterojunction photodetector. At a bias voltage of -5 V, the photodetector exhibits a responsivity of 1052 A/W, outperforming previous graphene-based heterojunction photodetectors by several orders of magnitude. The achieved detectivity of 3.13 × 1013 Jones and response time of 310 μs are also among the best values for graphene-based heterojunction photodetectors reported until date. Furthermore, even under zero bias, the photodetector demonstrates a high responsivity and detectivity of 1.04 A/W and 2.45 × 1012 Jones, respectively. The work shows a great potential of graphene nanoribbon-based photodetection technology.

CRISPR/Cas-Powered Amplification-Free Detection of Nucleic Acids: Current State of the Art, Challenges, and Futuristic Perspectives

CRISPR/Cas system is becoming an increasingly influential technology that has been repositioned in nucleic acid detection. A preamplification step is usually required to improve the sensitivity of CRISPR/Cas-based detection. The striking biological features of CRISPR/Cas, including programmability, high sensitivity and sequence specificity, and single-base resolution. More strikingly, the target-activated trans-cleavage could act as a biocatalytic signal transductor and amplifier, thereby empowering it to potentially perform nucleic acid detection without a preamplification step. The reports of such work are on the rise, which is not only scientifically significant but also promising for futuristic end-user applications. This review started with the introduction of the detection methods of nucleic acids and the CRISPR/Cas-based diagnostics (CRISPR-Dx). Next, we objectively discussed the pros and cons of preamplification steps for CRISPR-Dx. We then illustrated and highlighted the recently developed strategies for CRISPR/Cas-powered amplification-free detection that can be realized through the uses of ultralocalized reactors, cascade reactions, ultrasensitive detection systems, or others. Lastly, the challenges and futuristic perspectives were proposed. It can be expected that this work not only makes the researchers better understand the current strategies for this emerging field, but also provides insight for designing novel CRISPR-Dx without a preamplification step to win practicable use in the near future.

Rapid in situ RNA imaging based on Cas12a thrusting strand displacement reaction

RNA In situ imaging through DNA self-assembly is advantaged in illustrating its structures and functions with high-resolution, while the limited reaction efficiency and time-consuming operation hinder its clinical application. Here, we first proposed a new strand displacement reaction (SDR) model (Cas12a thrusting SDR, CtSDR), in which Cas12a could overcome the inherent reaction limitation and dramatically enhance efficiency through energy replenishment and by-product consumption. The target-initiated CtSDR amplification was established for RNA analysis, with order of magnitude lower limit of detection (LOD) than the Cas13a system. The CtSDR-based RNA in situ imaging strategy was developed to monitor intra-cellular microRNA expression change and delineate the landscape of oncogenic RNA in 66 clinic tissue samples, possessing a clear advantage over classic in situ hybridization (ISH) in terms of operation time (1 h versus 14 h) while showing comparable sensitivity and specificity. This work presents a promising approach to developing advanced molecular diagnostic tools.

A point-of-care platform for hair loss-related single nucleotide polymorphism genotyping

Rapid genotyping of single nucleotide polymorphism (SNP) is crucial for prognostics and disease management, enabling more rapid therapy selection and treatment determination. Here, we introduce a point-of-care platform for hair loss-related SNP genotyping based on allele-specific loop-mediated isothermal amplification (AS-LAMP) combined with naked-eye visualization. The specificity of the AS-LAMP assay was significantly enhanced by using mismatched allele-specific primers. AS-LAMP reaction and Schiff's reagent-based colorimetric detection were successfully performed using a thermoplastic genotyping chip. This strategy also showed potential for determining homozygotes and heterozygotes in a target sample. To assess SNP genotyping capacity, the genotyping chip was fabricated to visually detect rs6152 polymorphism of an androgen receptor gene associated with genetically induced hair loss. The genotyping platform rapidly identified the SNP within 40 min, and the detection limit was as low as 1 pg/μL of the target DNA contained in human serum. The introduced strategy showed high specificity and stability in discriminating low-abundance mutations, making it suitable as a portable and affordable point-of-care platform for rapid and accurate SNP discrimination applicable for bedside detection.

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.

CRISPR/dCas9-Mediated Specific Molecular Assembly Facilitates Genotyping of Mutant Circulating Tumor DNA

Breakthroughs in circulating tumor DNA (ctDNA) analysis are critical in tumor liquid biopsies but remain a technical challenge due to the double-stranded structure, extremely low abundance, and short half-life of ctDNA. Here, we report an electrochemical CRISPR/dCas9 sensor (E-dCas9) for sensitive and specific detection of ctDNA at a single-nucleotide resolution. The E-dCas9 design harnesses the specific capture and unzipping of target ctDNA by dCas9 to introduce a complementary reporter probe for specific molecular assembly and signal amplification. By efficient homogeneous assembly and interfacial click reaction, the assay demonstrates superior sensitivity (up to 2.86 fM) in detecting single-base mutant ctDNA and a broad dynamic range spanning 6 orders of magnitude. The sensor is also capable of measuring 10 fg/μL of a mutated target in excess of wild-type ones (1 ng/μL), equivalent to probing 0.001% of the mutation relative to the wild type. In addition, our sensor can monitor the dynamic expression of cellular genomic DNA and allows accurate analysis of blood samples from patients with nonsmall cell lung cancer, suggesting the potential of E-dCas9 as a promising tool in ctDNA-based cancer diagnosis.

CRISPR/Cas and Argonaute-Based Biosensors for Pathogen Detection

Over the past few decades, pathogens have posed a threat to human security, and rapid identification of pathogens should be one of the ideal methods to prevent major public health security outbreaks. Therefore, there is an urgent need for highly sensitive and specific approaches to identify and quantify pathogens. Clustered Regularly Interspaced Short Palindromic Repeats CRISPR/Cas systems and Argonaute (Ago) belong to the Microbial Defense Systems (MDS). The guided, programmable, and targeted activation of nucleases by both of them is leading the way to a new generation of pathogens detection. We compare these two nucleases in terms of similarities and differences. In addition, we discuss future challenges and prospects for the development of the CRISPR/Cas systems and Argonaute (Ago) biosensors, especially electrochemical biosensors. This review is expected to afford researchers entering this multidisciplinary field useful guidance and to provide inspiration for the development of more innovative electrochemical biosensors for pathogens detection.

Solid-Phase Collateral Cleavage System Based on CRISPR/Cas12 and Its Application toward Facile One-Pot Multiplex Double-Stranded DNA Detection

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 12 (Cas12) system is attracting interest for its potential as a next-generation nucleic acid detection tool. The system can recognize double-stranded DNA (dsDNA) based on Cas12-CRISPR RNA (crRNA) and induce signal transduction by collateral cleavage. This property is expected to simplify comprehensive genotyping. Here, we report a solid-phase collateral cleavage (SPCC) reaction by CRISPR/Cas12 and its application toward one-pot multiplex dsDNA detection with minimal operational steps. In the sensor, Cas12-crRNA and single-stranded DNA (ssDNA) are immobilized on the sensing surface and act as enzyme and reporter substrates, respectively. We also report a dual-target dsDNA sensor prepared by immobilizing Cas12-crRNA and a fluorophore-labeled ssDNA reporter on separate spots. When a spot captures a target dsDNA sequence, it cleaves the ssDNA reporter on the same spot and reduces its fluorescence by 42.1-57.3%. Crucially, spots targeting different sequences do not show a reduction in fluorescence, thus confirming the one-pot multiplex dsDNA detection by SPCC. Furthermore, the sequence specificity has a two-base resolution, and the detectable concentration for the target dsDNA is at least 10-9 M. In the future, the SPCC-based sensor array could achieve one-pot comprehensive genotyping by using an array spotter as a reagent-immobilizing method.

sEMG Spectral Analysis and Machine Learning Algorithms Are Able to Discriminate Biomechanical Risk Classes Associated with Manual Material Liftings

Manual material handling and load lifting are activities that can cause work-related musculoskeletal disorders. For this reason, the National Institute for Occupational Safety and Health proposed an equation depending on the following parameters: intensity, duration, frequency, and geometric characteristics associated with the load lifting. In this paper, we explore the feasibility of several Machine Learning (ML) algorithms, fed with frequency-domain features extracted from electromyographic (EMG) signals of back muscles, to discriminate biomechanical risk classes defined by the Revised NIOSH Lifting Equation. The EMG signals of the multifidus and erector spinae muscles were acquired by means of a wearable device for surface EMG and then segmented to extract several frequency-domain features relating to the Total Power Spectrum of the EMG signal. These features were fed to several ML algorithms to assess their prediction power. The ML algorithms produced interesting results in the classification task, with the Support Vector Machine algorithm outperforming the others with accuracy and Area under the Receiver Operating Characteristic Curve values of up to 0.985. Moreover, a correlation between muscular fatigue and risky lifting activities was found. These results showed the feasibility of the proposed methodology-based on wearable sensors and artificial intelligence-to predict the biomechanical risk associated with load lifting. A future investigation on an enriched study population and additional lifting scenarios could confirm the potential of the proposed methodology and its applicability in the field of occupational ergonomics.

Development of Single Molecule Techniques for Sensing and Manipulation of CRISPR and Polymerase Enzymes

Clustered regularly interspaced short palindromic repeats (CRISPR) and polymerases are powerful enzymes and their diverse applications in genomics, proteomics, and transcriptomics have revolutionized the biotechnology industry today. CRISPR has been widely adopted for genomic editing applications and Polymerases can efficiently amplify genomic transcripts via polymerase chain reaction (PCR). Further investigations into these enzymes can reveal specific details about their mechanisms that greatly expand their use. Single-molecule techniques are an effective way to probe enzymatic mechanisms because they may resolve intermediary conformations and states with greater detail than ensemble or bulk biosensing techniques. This review discusses various techniques for sensing and manipulation of single biomolecules that can help facilitate and expedite these discoveries. Each platform is categorized as optical, mechanical, or electronic. The methods, operating principles, outputs, and utility of each technique are briefly introduced, followed by a discussion of their applications to monitor and control CRISPR and Polymerases at the single molecule level, and closing with a brief overview of their limitations and future prospects.

CRISPR-Cas-Based Biomonitoring for Marine Environments: Toward CRISPR RNA Design Optimization Via Deep Learning

Almost all of Earth's oceans are now impacted by multiple anthropogenic stressors, including the spread of nonindigenous species, harmful algal blooms, and pathogens. Early detection is critical to manage these stressors effectively and to protect marine systems and the ecosystem services they provide. Molecular tools have emerged as a promising solution for marine biomonitoring. One of the latest advancements involves utilizing CRISPR-Cas technology to build programmable, rapid, ultrasensitive, and specific diagnostics. CRISPR-based diagnostics (CRISPR-Dx) has the potential to allow robust, reliable, and cost-effective biomonitoring in near real time. However, several challenges must be overcome before CRISPR-Dx can be established as a mainstream tool for marine biomonitoring. A critical unmet challenge is the need to design, optimize, and experimentally validate CRISPR-Dx assays. Artificial intelligence has recently been presented as a potential approach to tackle this challenge. This perspective synthesizes recent advances in CRISPR-Dx and machine learning modeling approaches, showcasing CRISPR-Dx potential to progress as a rising molecular tool candidate for marine biomonitoring applications.

CRISPR Assays for Disease Diagnosis: Progress to and Barriers Remaining for Clinical Applications

Numerous groups have employed the special properties of CRISPR/Cas systems to develop platforms that have broad potential applications for sensitive and specific detection of nucleic acid (NA) targets. However, few of these approaches have progressed to commercial or clinical applications. This review summarizes the properties of known CRISPR/Cas systems and their applications, challenges associated with the development of such assays, and opportunities to improve their performance or address unmet assay needs using nano-/micro-technology platforms. These include rapid and efficient sample preparation, integrated single-tube, amplification-free, quantifiable, multiplex, and non-NA assays. Finally, this review discusses the current outlook for such assays, including remaining barriers for clinical or point-of-care applications and their commercial development.

CRISPR-Based Biosensing Strategies: Technical Development and Application Prospects

Biosensing based on CRISPR-Cas systems is a young but rapidly evolving technology. The unprecedented properties of the CRISPR-Cas system provide an innovative tool for developing new-generation biosensing strategies. To date, a series of nucleic acid and non-nucleic acid detection methods have been developed based on the CRISPR platform. In this review, we first introduce the core biochemical properties underpinning the development of CRISPR bioassays, such as diverse reaction temperatures, programmability in design, high reaction efficiency, and recognition specificity, and highlight recent efforts to improve these parameters. We then introduce the technical developments, including how to improve sensitivity and quantification capabilities, develop multiplex assays, achieve convenient one-pot assays, create advanced sensors, and extend the applications of detection. Finally, we analyze obstacles to the commercial application of CRISPR detection technology and explore development opportunities and directions.

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.

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.

Progress and bioapplication of CRISPR-based one-step, quantitative and multiplexed infectious disease diagnostics

In Vitro Diagnosis (IVD) technology is able to accurately detect pathogens or biomarkers at an initial stage of disease, which works as an important toolbox for disease diagnosis. Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) system, as an emerging IVD method, plays a crucial role in the field of infectious disease detection due to its superior sensitivity and specificity. Recently, an increasing number of scientists have been devoted to improving the performance of CRISPR-based detection and on-site point-of-care testing (POCT) from extraction-free detection, amplification-free, modified Cas/crRNA complexes, quantitative assays, one-pot detection, and multiplexed platform. In this review, we describe the potential roles of these novel approaches and platforms in one-pot methods, quantitative molecular diagnostics as well as multiplexed detection. This review will not only help guide the full use of the CRISPR-Cas tools for quantification, multiplexed detection, POCT and as next-generation diagnostic biosensing platforms but also inspire new ideas, technological advances, and engineering strategies to address real-world challenges like the ongoing COVID-19 pandemic.

Electrochemical biosensors for analysis of DNA point mutations in cancer research

Cancer is a genetic disease induced by mutations in DNA, in particular point mutations in important driver genes that lead to protein malfunctioning and ultimately to tumorigenesis. Screening for the most common DNA point mutations, especially in such genes as TP53, BRCA1 and BRCA2, EGFR, KRAS, or BRAF, is crucial to determine predisposition risk for cancer or to predict response to therapy. In this review, we briefly depict how these genes are involved in cancer, followed by a description of the most common techniques routinely applied for their analysis, including high-throughput next-generation sequencing technology and less expensive low-throughput options, such as real-time PCR, restriction fragment length polymorphism, or high resolution melting analysis. We then introduce benefits of electrochemical biosensors as interesting alternatives to the standard methods in terms of cost, speed, and simplicity. We describe most common strategies involved in electrochemical biosensing of point mutations, relying mostly on PCR or isothermal amplification techniques, and critically discuss major challenges and obstacles that, until now, prevented their more widespread application in clinical settings.

Attomolar detection of hepatitis C virus core protein powered by molecular antenna-like effect in a graphene field-effect aptasensor

Biosensors based on graphene field-effect transistors have become a promising tool for detecting a broad range of analytes. However, their performance is substantially affected by the functionalization protocol. In this work, we use a controlled in-vacuum physical method for the covalent functionalization of graphene to construct ultrasensitive aptamer-based biosensors (aptasensors) able to detect hepatitis C virus core protein. These devices are highly specific and robust, achieving attomolar detection of the viral protein in human blood plasma. Such an improved sensitivity is rationalized by theoretical calculations showing that induced polarization at the graphene interface, caused by the proximity of covalently bound molecular probe, modulates the charge balance at the graphene/aptamer interface. This charge balance causes a net shift of the Dirac cone providing enhanced sensitivity for the attomolar detection of the target proteins. Such an unexpected effect paves the way for using this kind of graphene-based functionalized platforms for ultrasensitive and real-time diagnostics of different diseases.

CASMART, a one-step CRISPR Cas12a-mediated isothermal amplification for rapid and high-resolution digital detection of rare mutant alleles

Convenient, ultrasensitive, and accurate detection of rare variants is essential for early cancer diagnosis and precision medicine, however, despite years of efforts, tools that have all these qualities remain elusive. Here, we developed a one-step CRISPR/Cas12a-based digital diagnostic platform for accurately quantifying mutant alleles, referred to as the CRISPR ASsoaciated Mutation Allele Rapid Test (CASMART). The platform accurately quantifies the variant allele frequency of EGFR L858R within 1 h at 42 °C and can detect mutant targets as low as 0.3 copies/μL (0.498 aM) in mock multiplex cfDNA samples. We further investigated the applicability of CASMART using human genomic samples with confirmed EGFR L858R mutations previously measured variant allele frequency by next-generation sequencing. Comparison across platforms revealed equivalent detection performance (Pearson's correlation coefficient, R² = 0.9208) and high quantification accuracy for mutation allele frequency (intraclass correlation coefficient = 0.959). Our one-step approach enables easy and accurate variant allele frequency measurement of rare mutant alleles without PCR instrumentation, while the assay time was reduced by approximately half compared to the digital PCR with the shortest turnaround. The CASMART is an alternative to conventional single nucleotide polymorphism detection methods with great potential as a next-generation biosensor for rapidly quantifying the variant allele fraction, especially in resource-limited settings.

Amplification-free CRISPR/Cas detection technology: challenges, strategies, and perspectives

Rapid and accurate molecular diagnosis is a prerequisite for precision medicine, food safety, and environmental monitoring. The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas)-based detection, as a cutting-edged technique, has become an immensely effective tool for molecular diagnosis because of its outstanding advantages including attomolar level sensitivity, sequence-targeted single-base specificity, and rapid turnover time. However, the CRISPR/Cas-based detection methods typically require a pre-amplification step to elevate the concentration of the analyte, which may produce non-specific amplicons, prolong the detection time, and raise the risk of carryover contamination. Hence, various strategies for target amplification-free CRISPR/Cas-based detection have been developed, aiming to minimize the sensitivity loss due to lack of pre-amplification, enable detection for non-nucleic acid targets, and facilitate integration in portable devices. In this review, the current status and challenges of target amplification-free CRISPR/Cas-based detection are first summarized, followed by highlighting the four main strategies to promote the performance of target amplification-free CRISPR/Cas-based technology. Furthermore, we discuss future perspectives that will contribute to developing more efficient amplification-free CRISPR/Cas detection systems.