The CRISPR-Cas toolbox for analytical and diagnostic assay development

A competitive aptamer binding-based CRISPR-cas biosensor for sensitive detection of tetracycline residues in biological samples

Tetracycline (TC) is widely used in veterinary medicine and animal feed; however, TC residues in food pose a risk to human health. Thus, the sensitive and selective detection of TC is needed to ensure food safety. Herein, we developed a CRISPR-Cas12a biosensor with competitive aptamer binding to detect TC residues. The aptasensor, formed by hybridizing activator DNA with TC-specific aptamers on streptavidin-modified magnetic beads, releases activator DNA in a TC concentration-dependent manner. This activated the Cas12a-crRNA complex, which cleaved single-strand DNA reporters to generate a detectable fluorescence signal. The TC signal was amplified through a two-step incubation reaction, with a detection limit as low as 9.45 × 10-5 μg L-1. The assay showed high selectivity and good recovery rates in various biological samples (e.g., honey, milk, fish), demonstrating the applicability of the biosensors in pollutant detection.

A DNA concatemer-encoded CRISPR/Cas12a fluorescence sensor for sensitive detection of Pb2+ based on DNAzymes

Lead pollution presents a significant threat to ecological systems and human health, underscoring the urgent need for highly sensitive detection methods. Herein, we introduce a novel DNA concatemer-encoded CRISPR/Cas12a fluorescence sensor (MDD-Cas12a) for sensitive detection of Pb2+ based on DNAzymes. To accomplish this, we designed a substrate strand containing a long DNA concatemer encoding multiple protospacer adjacent motifs (PAMs) and protospacer sequences for activation of the CRISPR/Cas12a system. The DNA concatemer was subsequently anchored to the surface of magnetic beads (MBs) to fabricate a MBs-DNA concatemer nanoprobe. In the presence of Pb2+, the DNAzyme structure catalyzes the cleavage of the substrate strand, leading to the release of DNA concatemers. Following magnetic separation, the released DNA concatemers significantly activate the non-specific trans-cleavage activity of the Cas12a/crRNA complex. The fluorescence reporter DNA is then completely cleaved by the activated Cas12a/crRNA complex, and the Pb2+ concentration in the sample can be quantified by measuring the fluorescence signal. By harnessing the specific recognition capability of DNAzymes for Pb2+, the programmability of DNA concatemers, and the self-amplification features of the CRISPR/Cas12a system, the MDD-Cas12a platform demonstrates high sensitivity and specificity for detecting Pb2+ in milk and lake water samples.

Programmable AIESTA: All-in-One Isothermal Enzymatic Signal Transduction Amplifier for Portable Profiling

The Argonaute (Ago) protein exhibits high specificity in nucleic acid recognition and cleavage, making it highly promising for biosensing applications. Its potential is further enhanced by its independence from protospacer adjacent motif (PAM) requirements and the cost-effectiveness of using short DNA guides. Both Ago and CRISPR/Cas systems face challenges in signal amplification, which limit their ability to detect targets at ultralow concentrations. To overcome this limitation, a thermostable quadratic amplification system (T-QAS) was constructed by integrating a thermostable nicking-enzyme-mediated amplification (NEMA) strategy with TtAgo. The system leverages the high stability of T-QAS at elevated temperatures to enhance guide-target interactions and decrease false positives caused by nonspecific amplification. Additionally, nanozyme is integrated with T-QAS to construct the AIESTA platform (all-in-one isothermal enzymatic signal transduction amplifier), which is a single-tube visual sensing platform. Within the AIESTA system, T-QAS improves specificity through high operational temperatures and offers programmable functions, enabling the sensitive detection of miRNA and foodborne toxins. The combination of T-QAS and nanozyme makes AIESTA a candidate of point-of-care testing (POCT) field, showcasing the potential for biosensing in resource-limited and complex environments.

CRISPR/Cas12a Protein Switch Powered Label-Free Electrochemical Biosensor for Sensitive Viral Protease Detection

Viral proteases are critical molecular targets in viral pathogenesis, representing pivotal biomarkers for understanding viral infection mechanisms and developing antiviral therapeutics. This study introduces a label-free electrochemical biosensor that enables sensitive viral protease detection by integrating protease-responsive CRISPR/Cas protein switches (CasPSs) with a hemin aptamer-functionalized electrochemical interface. The biosensor's mechanism relies on viral protease-mediated proteolysis, which leads to the release of active Cas12a proteins from CasPSs and generates amplified electrochemical responses through continuous cleavage of immobilized redox-active hemin/aptamer complexes. This biosensor achieved specific hepatitis C virus NS3/4A protease sensing with femtomolar sensitivity and could be readily expanded to other viral proteases by replacing the CasPS module. The feasibility of this biosensor was demonstrated by monitoring enterovirus 71 3C protease activities in virus-infected cell samples with different viral loads and postinfection times. This study provides a promising strategy for integrating CRISPR biosensing with electrochemical platforms, offering a helpful analytical tool for viral infection monitoring and antiviral drug screening.

Integrating CRISPR-Cas12a with Aptamer as a Logic Gate Biosensing Platform for the Detection of CD33 and CD123

Molecular logic gates, as biomolecule-based computational systems, are highly suitable for multitarget detection due to their programmability and modularity. However, existing systems are primarily limited to nucleic acid detection and have not been widely applied to disease-related sensing, particularly for disease antigens. CD33 and CD123 are critical biomarkers for acute myeloid leukemia (AML), yet conventional detection methods rely on expensive equipment and complex procedures, limiting their accessibility and practicality. This study designs a DNA logic gate system integrating nucleic acid aptamers, catalytic hairpin assembly (CHA), and CRISPR-Cas12a, pioneering its use for AML antigen detection. The system comprises three modules: input recognition, signal amplification, and signal transduction. Nucleic acid aptamers specifically identify CD33 and CD123, while CHA enables efficient signal amplification and CRISPR-Cas12a generates a fluorescent output via trans-cleavage activity. The system operates stably at room temperature and implements multiple logic gate models, including YES, OR, AND, NOR, and INHIBIT, enabling the simultaneous detection of CD33 and CD123. Experimental results are visually distinguishable under blue light, and the system requires only standard fluorescence detection instruments. In serum samples, it exhibits excellent selectivity and stability, with a detection limit of 0.5 ng/mL. This study pioneers the application of logic gate technology for disease antigen detection, addressing a critical gap in AML biomarker sensing. Our study indicates that this logic detection platform, characterized by its simplicity in operation, high sensitivity, and versatility in logic functions, holds promise as a potent sensing system for the intelligent multiplex target detection of disease antigens, environmental pollutants, and heavy metals.

A multi-functional synergistic platform of Cas12a split dsDNA activators

This work comprehensively explores the effects of various positions of Cas12a split activators. Based on this, a multi-functional synergistic platform was constructed. The construction of a structural dynamic network, the sensitive detection of APE1, and a time-controlled photo-activation have been achieved, demonstrating the potential for expanding Cas12a applications.

Point-of-need species identification using non-PCR DNA-based approaches to combat wildlife crime

Wildlife crime, defined as any unlawful exploitation and trade of wildlife, is a lucrative illegal global industry, along with narcotics and weapons trafficking. It encompasses the harvest, transport, exchange, and end use of wildlife or wildlife-derived products. Regulated internationally by the Convention on the International Trade in Endangered Species of Flora and Fauna (CITES, 1973), wildlife crime is primarily detected using morphological or DNA sequencing methods. However, there is a growing demand for rapid, portable, and cost-effective screening tools to bypass time-consuming workflows and specialist laboratory equipment. Point-of-need testing, particularly at wildlife hotspots like international borders, offers a promising solution for the swift detection of illegal activities. Isothermal amplification methods such as loop mediated isothermal amplification (LAMP), rolling circle amplification (RCA), and recombinase polymerase amplification (RPA), are favoured for their low resource needs compared to traditional PCR. These methods can be combined with target detection methods such as clustered regularly interspaced short palindromic repeats (CRISPR) and aptamers to enhance sensitivity. Integrating these methods with others, such as lateral flow assays (LFA) and microfluidic devices, simplifies sample preparation and visualisation. Already established in disease diagnosis and food safety, these innovations in genetic testing provide rapid, on-site detection. When applied to wildlife crime, they can serve as tools to complement traditional PCR and sequencing methods. This review explores how non-PCR based approaches could offer faster, simpler, and more cost-effective solutions to combat wildlife crime.

Origami Paper-Based Immunoassay Device with CRISPR/Cas12a Signal Amplification

In clinical diagnosis, the determination of target proteins at low concentration levels is generally performed by immunoassays, such as the enzyme-linked immunosorbent assay (ELISA), which is a time-consuming process. To date, paper-based ELISA platforms enabling faster and less expensive analysis have been developed, but their important issue for clinical applications is the limited sensitivity compared to conventional ELISA. To address this challenge, this paper introduces a simple, rapid, and highly sensitive detection method for non-nucleic acid targets achieved by integrating the CRISPR/Cas12a system into paper-based ELISA. An origami-type paper-based device enabling simple assay operation has been designed, and the detection of targets on the paper substrates is based on observing the fluorescence signal induced by the CRISPR/Cas12a enzyme cleaving a probe single-stranded DNA (ssDNA) labeled with fluorophore and quencher (FQ reporter). To enhance sensitivity, antibodies labeled with a network of multiple DNA activating the CRISPR/Cas12a enzyme have been utilized as detection antibodies. As a result, the developed device successfully boosted the detection sensitivity for both human IgG and the hepatitis B virus surface antigen (HBsAg). In particular, the limit of detection (LOD) for HBsAg was estimated to be 12 pg/mL, representing over 10-fold higher sensitivity compared with commercially available HBsAg ELISA kits (LOD: 200 pg/mL). In addition, the fluorescence response toward porcine whole blood samples containing different HBsAg concentrations was also confirmed by capturing images with a smartphone, followed by quantitative data analysis. These results demonstrate the potential applicability of the proposed platform for clinical tests at the point of care.

PAM-Independent CRISPR-Cas12a System for Specific Assays of Single Nucleotide Variants

The CRISPR-Cas12a system has been extensively utilized in nucleic acid detection owing to its remarkable sensitivity and specificity. Nonetheless, its strict dependency on the presence of a protospacer adjacent motif (PAM) within double-stranded DNA (dsDNA) introduces considerable limitations, thereby constraining its applicability, flexibility, and broader accessibility in molecular diagnostics. Here, we communicate a universal, robust, and high-fidelity method for a PAM-independent nucleic acid assay based on the CRISPR-Cas12a system, named TRACER (mutant target-recognized PAM-independent CRISPR-Cas12a enzyme reporting system). TRACER can effectively distinguish target nucleic acids at concentrations as low as 0.5 aM, thereby enabling it to identify the presence of a 0.1% single nucleotide variant (SNV)-included mutant-type gene in heterozygotes. Thus, TRACER exhibits comparable sensitivity, specificity, and accuracy to Sanger sequencing in analyzing the SNV-related clinical tumor samples. Overall, TRACER introduces a brand-new perspective for SNV assays by eliminating the dependency on PAM sites and significantly expands the application range of the CRISPR-Cas12a system, thus holding immense potential for clinical diagnostics, biomedical research, and drug discovery.

CRISPR/Cas System-Based Fluorescent Sensor for Analysis and Detection

Fluorescent sensor is an important tool to reliaze qualitative or quantitative detection of target analyte based on the fluorescence principle. Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) has been utilized to develop as a precise, efficient, and highly sensitive molecular diagnostic tool due to its efficient targeting and gene editing ability. At present, CRISPR/Cas system-based fluorescent sensors have shown excellent performance in the field of analysis and detection, and have received widespread attention. Therefore, this paper reviews the mechanism of the CRISPR/Cas system, the characteristics of different Cas proteins, and the principle and characteristics of the fluorescent sensor, with a focus on summarizing the application of the CRISPR/Cas system-based fluorescent sensor for analysis and detection.

Spatial double-layer hydrogels enabled visual detection of Cladobotryum mycophilum based on recombinase-aided amplification - CRISPR/Cas12a

Cladobotryum mycophilum, a pathogen responsible for cobweb disease, caused significant and irreversible losses in the mushroom industry. Effective monitoring and early prevention rely on the development of advanced diagnosis methods. This study introduced a novel hydrogel-based C. mycophilum detection method that integrates recombinase-aided amplification (RAA) with the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) system (CRISPR/Cas12a), referred as RCCH. The RAA reaction occurs within cross-linked PEG hydrogel, which is subsequently overlaid with a CRISPR/Cas12a-functionalized hydrogel. The porous network of the PEG hydrogel traps essential enzymes, facilitating spatial co-localization of target DNA and the CRISPR/Cas12a-crRNA complex. Upon activation of Cas12a's trans-cleavage activity, clear and countable fluorescent spots are generated for visual detection. RCCH demonstrates a limit of detection as low as 1 fg/μL, and exceptional selectivity against common fungi Trichoderma viride and T. harzianum and the host mushroom Lentinula edodes. The entire process is completed in under 40 min, indicating RCCH's potential as a rapid, accurate, and practical detection method for monitoring mushroom diseases. This innovative approach offers significant support for enhancing safety in the mushroom industry.

CRISPR/HCR-powered ratiometric fluorescence aptasensor for ochratoxin A detection

To address the need for highly sensitive and reliable detection of trace ochratoxin A (OTA) in food matrices, we developed a ratiometric fluorescent aptasensor by integrating CRISPR/Cas12a, hybridization chain reaction (HCR), and horseradish peroxidase (HRP)-induced inner filter effect (IFE). The mechanism involves OTA releasing an activator that initiates CRISPR/Cas12a trans-cleavage, blocking HCR assembly. This reduces HRP levels, limiting the conversion of o-phenylenediamine (OPD) to fluorescent 2,3-diaminophenazine (DAP) (emitting at 562 nm) while maintaining strong emission from 2-amino terephthalic acid (BDC-NH2) at 426 nm. The F426/F562 ratio serves as a "signal-on" indicator, enabling sensitive OTA detection over 0.1 pM to 10 nM, with a detection limit of 0.0417 pM. The method exhibits excellent reproducibility, with intra-day and inter-day relative standard deviations (RSDs) of 1.91 %-3.87 % and 1.79 %, respectively, along with recovery rates of 90.1 %-110.6 % in real samples. These advantages highlight its significant potential for CRISPR/Cas-based OTA detection.

Single-tube detection of a foodborne bacterial pathogen using user-friendly portable device

Timely and reliable detection of foodborne bacterial pathogen is crucial for reducing disease burden in low- and middle-income countries. However, laboratory-based methods are often inaccessibility in resource-limited settings. Here, we developed a single-tube assay and a low-cost palm-sized device for on-site detection of the representative foodborne bacterial pathogen, Salmonella Enteritidis. Our assay incorporates the advantages of protein-nucleic acid signal transduction, EXPonential Amplification Reaction (EXPAR), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 12a (Cas12a). After systematically investigating the compatibility of these components, we developed a "three-in-one" integration reaction, termed ST-EXPAR-CRISPR assay. This assay requires only one tube, one controlled temperature (39 °C) and simple operation, eliminating the need for bacterial isolation, nucleic acid extraction, or washing steps. ST-EXPAR-CRISPR assay is capable of detecting as few as 37 CFU/mL of target bacterium. Using our kit and portable device, untrained volunteers successfully detected contamination in food samples outdoors. The simplicity of the detection process and minimal hardware requirements make our assay highly promising for application in point-of-care and on-site scenarios. Moreover, the ST-EXPAR-CRISPR assay can be easily modified to detect other targets by changing the nucleic acid sequence with low research and development cost, potentially reducing the global disease burden.

Fluorescent/colorimetric dual-mode for detecting of MC-LR using bidirectional RCA coupled with CdTe QDs

A fluorescent/colorimetric dual-mode biosensor was designed using CdTe QDs and CRISPR/Cas for the efficient and ultrasensitive detection of microcystin-leucine-arginine (MC-LR). The biosensor mainly activates the trans-cleavage activity of Cas12a through nucleic acid amplification technology, such as bidirectional rolling circle amplification (B-RCA), to perform signal conversion, release Ag+ from the cleaving hairpin, quench QD fluorescence, and perform signal presentation. The biosensor can perform fluorometric and colorimetric detection, enabling rapid field assays. It exhibits enhanced selectivity, increased sensitivity, and greater accuracy. The optimal conditions yield a detection range from 0.05 to 500 nM, with a minimum detectable concentration of 2.137 pM, surpassing the performance of traditional methods. The biosensor can effectively detect MC-LR in actual environmental samples. Overall, this study provided a general detection approach for the application of nucleic acid detection technology to detect trace pollutants in the environment.

From Origin to the Present: Establishment, Mechanism, Evolutions and Biomedical Applications of the CRISPR/Cas-Based Macromolecular System in Brief

Advancements in biological and medical science are intricately linked to the biological central dogma. In recent years, gene editing techniques, especially CRISPR/Cas systems, have emerged as powerful tools for modifying genetic information, supplementing the central dogma and holding significant promise for disease diagnosis and treatment. Extensive research has been conducted on the continuously evolving CRISPR/Cas systems, particularly in relation to challenging diseases, such as cancer and HIV infection. Consequently, the integration of CRISPR/Cas-based techniques with contemporary medical approaches and therapies is anticipated to greatly enhance healthcare outcomes for humans. This review begins with a brief overview of the discovery of the CRISPR/Cas system. Subsequently, using CRISPR/Cas9 as an example, a clear description of the classical molecular mechanism underlying the CRISPR/Cas system was given. Additionally, the development of the CRISPR/Cas system and its applications in gene therapy and high-sensitivity disease diagnosis were discussed. Furthermore, we address the prospects for clinical applications of CRISPR/Cas-based gene therapy, highlighting the ethical considerations associated with altering genetic information. This brief review aims to enhance understanding of the CRISPR/Cas macromolecular system and provide insight into the potential of genetic macromolecular drugs for therapeutic purposes.

A CRISPR/Cas12a-based competitive aptasensor for ochratoxin A detection

The serious contamination of ochratoxin A (OTA) in agricultural products has promoted the development of rapid, sensitive, and selective analytical methods for OTA monitoring. We demonstrated a competitive aptasensor for OTA detection using CRISPR/Cas12a as an effective signal amplifier. OTA competes with complementary DNA of the aptamer on the microplate to bind to the aptamer. Streptavidin bridges the biotinylated aptamer and biotinylated activator to convert the OTA input into Cas12a activation, which cleaves fluorescent DNA reporters. Under optimized experimental conditions, the aptasensor was demonstrated to work well for sensitive detection of OTA, with a linear range from 0.5 nM to 62.5 nM and a detection limit of 0.5 nM. Moreover, our method not only exhibits high selectivity, but also has satisfactory anti-interference ability against complex sample matrices. Taken together, the CRISPR/Cas12a-based competitive aptasensor offers a simple and sensitive platform for OTA detection, and it holds great promise for food security monitoring.

CRISPR in clinical diagnostics: bridging the gap between research and practice

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) has transformed molecular biology through its precise gene-editing capabilities. Beyond its initial applications in genetic modification, CRISPR has emerged as a powerful tool in diagnostics and biosensing. This review explores its transition from genome editing to innovative detection methods, including nucleic acid identification, single nucleotide polymorphism (SNP) analysis, and protein sensing. Advanced technologies such as SHERLOCK and DETECTR demonstrate CRISPR's potential for point-of-care diagnostics, enabling rapid and highly sensitive detection. The integration of chemical modifications, CRISPR-Chip technology, and enzymatic systems like Cas12a and Cas13a enhances signal amplification and detection efficiency. These advancements promise decentralized, real-time diagnostic solutions with significant implications for global healthcare. Furthermore, the fusion of CRISPR with artificial intelligence and digital health platforms is paving the way for more accessible, cost-effective, and scalable diagnostic approaches, ultimately revolutionizing precision medicine.

Emerging Combination of Hydrogel and Electrochemical Biosensors

Electrochemical sensors are among the most promising technologies for biomarker research, with outstanding sensitivity, selectivity, and rapid response capabilities that make them important in medical diagnostics and prognosis. Recently, hydrogels have gained attention in the domain of electrochemical biosensors because of their superior biocompatibility, excellent adhesion, and ability to form conformal contact with diverse surfaces. These features provide distinct advantages, particularly in the advancement of wearable biosensors. This review examines the contemporary utilization of hydrogels in electrochemical sensing, explores strategies for optimization and prospective development trajectories, and highlights their distinctive advantages. The objective is to provide an exhaustive overview of the foundational principles of electrochemical sensing systems, analyze the compatibility of hydrogel properties with electrochemical methodologies, and propose potential healthcare applications to further illustrate their applicability. Despite significant advances in the development of hydrogel-based electrochemical biosensors, challenges persist, such as improving material fatigue resistance, interfacial adhesion, and maintaining balanced water content across various environments. Overall, hydrogels have immense potential in flexible biosensors and provide exciting opportunities. However, resolving the current obstacles will necessitate additional research and development efforts.

Expanding Cas12a Activity Control with an RNA G-Quadruplex at the 5' end of CRISPR RNA

Precise control of Cas12a activity is essential for the improvement of the detection limit of clinical diagnostics and the minimization of errors. This study addresses the challenge of controlling Cas12a activity, especially in the context of nucleic acid detection where the inherent incompatibility between isothermal amplification and CRISPR reactions complicates accurate diagnostics. An RNA G-quadruplex (RG4) structure at the 5' end of crRNA is introduced to modulate Cas12a activity accurately without the need for chemical modifications. The results indicate that the presence of RG4 does not significantly impact Cas12a's cleavage activity but can be controlled by RG4 stabilizers, enabling the suppression and subsequent restoration of Cas12a activity with potential for precise activity control. Moreover, the use of RG4 is expanded by incorporating it into split crRNA, introducing RG4 directly at the 5' end of the direct repeat (DR) region, enabling tailored activity regulation for different targets by matching with various Spacer regions. Additionally, a light-controlled one-pot method for activating Cas12a is developed, thereby enhancing the accuracy and sensitivity of clinical samples. This study showcases the pioneering use of RG4 in manipulating Cas12a activity, streamlining diagnostics, and paving the way for advances in clinical nucleic acid testing.

Direct repeat region 3' end modifications regulate Cas12a activity and expand its applications

CRISPR-Cas12a technology has transformative potential, but as its applications grow, enhancing its inherent functionalities is essential to meet diverse demands. Here, we reveal a regulatory mechanism for LbCas12a through direct repeat (DR) region 3' end modifications and de-modifications, which can regulate LbCas12a's cis- and trans-cleavage activities. We extensively explored the effects of introducing phosphorylation, DNA, photo-cleavable linker, DNA modifications at the DR 3' end on LbCas12a's functionality. We find that the temporary inhibitory function of Cas12a can be reactivated by DR 3' end modification corresponding substances, such as alkaline phosphatase (ALP), immunoglobulin G (IgG), alpha-fetoprotein (AFP), DNA exonucleases, ultraviolet radiation, and DNA glycosylases, which greatly expand the scope of application of Cas12a. Clinical applications demonstrated promising results in ALP, AFP, and trace Epstein-Barr virus detection compared to gold standard methods. Our research provides valuable insights into regulating LbCas12a activity through direct modification of DR and significantly expands its potential clinical detection targets, paving the way for future universal clustered regularly interspaced short palindromic repeats (CRISPR) diagnostic strategies.

Developing a Versatile Arsenal: Novel Antimicrobials as Offensive Tools Against Pathogenic Bacteria

The pervasive and often indiscriminate use of antibiotics has accelerated the emergence of drug-resistant bacterial strains, thus presenting an acute threat to global public health. Despite a growing acknowledgment of the severity of this crisis, the current suite of strategies to mitigate antimicrobial resistance remains markedly inadequate. This paper asserts the paramount need for the swift development of groundbreaking antimicrobial strategies and provides a comprehensive review of an array of innovative techniques currently under scrutiny. Among these, nano-antimicrobials, antimicrobials derived from ribosomal proteins, CRISPR/Cas-based systems, agents that undermine bacterial bioenergetics, and antimicrobial polysaccharides hold particular promise. This analysis gives special attention to CRISPR/Cas-based antimicrobials, scrutinizing their underlying mechanisms, exploring their potential applications, delineating their distinct advantages, and noting their likely limitations. Furthermore, we extend our exploration by proposing theoretical advancements in antimicrobial technology and evaluating feasible methods for the effective delivery of these agents. This includes leveraging these advances for broader biomedical applications, potentially revolutionizing how we confront bacterial pathogens in the future, and laying a foundation for extended research in multimodal therapeutic strategies.

Current biosensing strategies based on in vitro T7 RNA polymerase reaction

Recently, a unique behavior of T7 RNA polymerase has expanded its functionality as a biosensing platform. Various biosensors utilizing T7 RNA polymerase, combined with fluorescent aptamers, electrochemical probes, or CRISPR/Cas systems, have been developed to detect analytes, including nucleic acids and non-nucleic acid target, with high specificity and low detection limits. Each approach demonstrates unique strengths, such as real-time monitoring and minimal interference, but also presents challenges in stability, cost, and reaction optimization. This review provides an overview of T7 RNA polymerase's role in biosensing technology, highlighting its potential to advance diagnostics and molecular detection in diverse fields.

'Splice-at-will' Cas12a crRNA engineering enabled direct quantification of ultrashort RNAs

We present a robust 'splice-at-will' CRISPR RNA (crRNA) engineering mechanism that overcomes the limitations of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system in directly detecting ultrashort RNAs. In this strategy, an intact Cas12a crRNA can be split from almost any site of the spacer region to obtain a truncated crRNA (tcrRNA) that cannot activate Cas12a even after binding an auxiliary DNA activator. While splicing tcrRNAs with a moiety of ultrashort RNA, the formed combination can work together to activate Cas12a efficiently, enabling 'splice-at-will' crRNA engineering. Importantly, the 'splice-at-will' crRNA exhibits almost the same trans-cleavage activation efficiency as that of a conventional intact crRNA. Therefore, by rationally designing a DNA auxiliary activator with a conserved tcrRNA-complementary sequence and an arbitrary short RNA-of-interest recognition domain, a general sensing system is established that directly utilizes traditional DNA-activated Cas12a to detect ultrashort RNAs. This 'splice-at-will' crRNA engineering strategy could faithfully detect ultrashort RNA sequences as short as 6-8 nt, which cannot be achieved by conventional Cas12a and Cas13a systems. Additionally, through flexible splicing site design, our method can precisely distinguish single-base differences in microRNA and other short RNA sequences. This work has significantly expanded the Cas12a-based diagnostic toolbox and opened new avenues for ultrashort RNA detection.

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.

Phase Transition of Wax Enabling CRISPR Diagnostics for Automatic At-Home Testing of Multiple Sexually Transmitted Infection Pathogens

Sexually transmitted infections (STIs) significantly impact women's reproductive health. Rapid, sensitive, and affordable detection of these pathogens is essential, especially for home-based self-testing, which is crucial for individuals who prioritize privacy or live in areas with limited access to healthcare services. Herein, an automated diagnostic system called Wax-CRISPR has been designed specifically for at-home testing of multiple STIs. This system employs a unique strategy by using the solid-to-liquid phase transition of wax to sequentially isolate and mix recombinase polymerase amplification (RPA) and CRISPR assays in a microfluidic chip. By incorporating a home-built controlling system, Wax-CRISPR achieves true one-pot multiplexed detection. The system can simultaneously detect six common critical gynecological pathogens (CT, MG, UU, NG, HPV 16, and HPV 18) within 30 min, with a detection limit reaching 10-18 M. Clinical evaluation demonstrates that the system achieves a sensitivity of 96.8% and a specificity of 97.3% across 100 clinical samples. Importantly, eight randomly recruited untrained operators performe a double-blinded test and successfully identified the STI targets in 33 clinical samples. This wax-transition-based one-pot CRISPR assay offers advantages such as low-cost, high-stability, and user-friendliness, making it a useful platform for at-home or field-based testing of multiple pathogen infections.

DNA self-assembly-boosted transcription amplification coupled with CRISPR/Cas13a system for plant microRNA analysis

MicroRNAs (miRNAs) play important roles in the growth process of plants, and some food-originated plant miRNAs have potential impacts on human health, which makes the detection of plant miRNAs of great significance. However, plant miRNAs are naturally modified with 2'-O-methyl at the 3'-terminal, which is difficult to be directly quantified by enzyme-catalyzed terminal polymerization protocols. Herein, we have proposed a simple strategy by coupling DNA self-assembly-boosted transcription amplification with CRISPR/Cas13a platform (termed as Cas13a-SATA) for the specific and sensitive detection of plant miRNA. In the Cas13a-SATA, the plant miRNA will mediate DNA self-assembly on the surface of microbeads and then trigger efficient transcription amplification to yield numerous single-stranded RNA (ssRNA) molecules, which can effectively activate the Cas13a trans-cleavage activity to generate intense fluorescence signal in a plant miRNA dosage-responsive manner. Using the Cas13a-SATA, we have realized the sensitive detection of plant miR156a with the limit of detection (LOD) down to 3.8 fM. Furthermore, Cas13a-SATA has been successfully applied to the accurate quantification of miR156a in Arabidopsis and maize, demonstrating its feasibility in analyzing plant miRNAs in real biological samples.

CRISPR/Cas12a Corona Nanomachine for Detecting Circulating Tumor Nucleic Acids in Serum

Circulating tumor nucleic acids (CTNAs), which consist of cell-free DNA or RNA released from tumor cells, are utilized as potential biomarkers for diagnosing and managing tumor prognosis. There is a significant demand for developing a highly sensitive and reliable assay for CTNAs detection. In this study, we engineered a CRISPR/Cas12a corona nanomachine capable of detecting circulating tumor DNA and RNA in serum. This nanomachine consists of a protein shell incorporating Cas12a/crRNA ribonucleoprotein complexes and a scaffold AuNP core decorated with substrate ssDNA strands. The protective CRISPR corona shields the nucleic acid core from degradation by nuclease DNase/RNase, thereby enhancing the stability of the CRISPR/Cas12a corona nanomachine in biological fluids, even tolerating up to undiluted human serum and FBS. Upon encountering target CTNAs, the CRISPR/Cas12a is activated through the sequence-specific hybridization between crRNA and CTNAs. Subsequently, the activated CRISPR/Cas12a autonomously cleaves the collateral ssDNA substrates on AuNPs, releasing the fluorophore-labeled fragment and generating an increasing fluorescent signal. The CRISPR corona nanomachine was successfully employed to detect various CTNAs, including circulating tumor (ct)DNA/RNA (EGFR L858R) and microRNA-21, achieving a limit of detection of 0.14 pM for ctDNA and 1.0 pM for RNA. This CRISPR corona nanomachine enables simultaneous detection of both DNA and RNA in complex biological samples, offering a promising tool for early diagnosis.

Machine Learning-Assisted, Dual-Channel CRISPR/Cas12a Biosensor-In-Microdroplet for Amplification-Free Nucleic Acid Detection for Food Authenticity Testing

The development of novel detection technology for meat species authenticity is imperative. Here, we developed a machine learning-supported, dual-channel biosensor-in-microdroplet platform for meat species authenticity detection named CC-drop (CRISPR/Cas12a digital single-molecule microdroplet biosensor). This strategy allowed us to quickly identify and analyze animal-derived components in foods. This biosensor was enabled by CRISPR/Cas12a-based fluorescence lighting-up detection, and the nucleic acid signals can be recognized by a Cas12a-crRNA binary complex to trigger the trans-cleavage of any by-stander reporter single-stranded (ss) DNA, in which nucleic acid signals can be converted and amplified to fluorescent readouts. The ultralocalized microdroplet reactor was constructed by reducing the reaction volume from up to picoliter to accommodate the aforementioned reaction to further enhance the sensitivity to even render an amplification-free nucleic acid detection. Moreover, we established a smartphone App coupled with a random forest machine learning model based on parameters such as area, fluorescent intensity, and counting number to ensure the accuracy of image recording and processing. The sample-to-result time was within 80 min. Importantly, the proposed biosensor was able to accurately detect the ND1 (pork-specific) and IL-2 (duck-specific) genes in deep processed meat-derived foods that usually had truncated DNA, and the results were more robust and practical than conventional real-time polymerase chain reaction after a side-by-side comparison. All in all, the proposed biosensor can be expected to be used for rapid food authenticity and other nucleic acid detections in the future.

CRISPR-based dual-aptamer proximity ligation coupled hybridization chain reaction for precise detection of tumor extracellular vesicles and cancer diagnosis

Tumor cell-derived extracellular vesicles (TEVs) contain numerous cellular molecules and are considered potential biomarkers for non-invasive liquid biopsy. However, due to the low abundance of TEVs secreted by tumor cells and their phenotypic heterogeneity, there is a lack of sensitive and specific methods to quantify TEVs. Here, we developed a dual-aptamer proximity ligation-coupled hybridization chain reaction (HCR) method for tracing TEVs, exploiting CRISPR to achieve highly sensitive detection. Taking advantage of the high binding affinity of aptamers, the two aptamers (AptEpCAM, AptHER2) exhibited the high selectivity for TEVs recognition. HCR generated long-repeated sequence containing multiple crRNA targetable barcodes, and the signals were further amplified by CRISPR upon recognizing the HCR sequences, thereby enhancing the sensitivity. Under optimal conditions, the developed method demonstrated a favorable linear relationship in the range of 2 × 103-107 particles/μL, with a limit of detection (LOD) of 3.3 × 102 particles/μL. We directly applied our assay to clinical plasma analysis, achieving 100 % accuracy in cancer diagnosis, thus demonstrating the potential clinical applications of TEVs. Due to its simplicity and rapidity, excellent sensitivity and specificity, this method has broad applications in clinical medicine.

A nanopore-based label-free CRISPR/Cas12a system for portable and ultrasensitive detection of zearalenone

BACKGROUND

Food safety has become a serious global concern. Therefore, there is a need for effective detection technologies in this field. Currently, the development of effective on-site detection techniques is extremely important for food safety. However, the traditional on-site detection methods currently lack effective signal amplification. Herein, the aim of this study was to construct a nanopore-based label-free CRISPR/Cas12a system for the detection of Zearalenone (ZEN). The method is expected to be highly sensitive for portable detection of ZEN in food.

RESULTS

The proposed strategy was mainly involved three steps, including the displacement of the target DNA, the triggering of the cleavage of hairpin DNA probes (probes 1) by the trans-cleavage of CRISPR/Cas12a, and the generation of a measurable nanopore current signal. The probes 1 and DNA after the cleavage of probes 1 (probes 2) produce different characteristic nanopore signals as they pass through the nanopore. The established method achieved a low limit of detection (LOD) of 6.52 fM for ZEN and a wide liner range under optimized conditions. Furthermore, the practical applicability of this method was verified in real maize samples and showed good recoveries (90.68-101.98 %) and low relative standard deviations (RSD) (9.21-9.72 %). Therefore, this method is a promising option for rapid and ultrasensitive detection of ZEN.

SIGNIFICANCE AND NOVELTY

The study presented a portable nanopore-based CRISPR/Cas12a signal amplification detection system for the detection of ZEN in food, which had a low LOD and the advantages of rapid, portability, and on-site detection potential. In conclusion, the method presented a promising prospect and universal platform for the detection of ZEN and other mycotoxins, offering a novel insight into on-site food safety detection.

CRISPR/Cas12a assay for amol level microRNA by combining enzyme-free amplification and single particle analysis

CRISPR/Cas systems are increasingly utilized for sensitive miRNA detection through enzyme-based pre-amplification. To address challenges such as high costs, non-specific amplification, and interference from primer residues in pre-amplification strategies, herein a dual amplification CRISPR miRNA assay was developed by combining enzyme-free HCR with single-particle analysis. Attomolar detection limits, excellent selectivity, and practicability were achieved by applying this method.

Unveiling Cas12j Trans-Cleavage Activity for CRISPR Diagnostics: Application to miRNA Detection in Lung Cancer Diagnosis

Cas12j, a hypercompact and efficient Cas protein, has potential for use in CRISPR diagnostics, but has not yet been used because the trans-cleavage activity of Cas12j is veiled. Here, the trans-cleavage behavior of Cas12j1, 2, and 3 variants and evaluate their suitability for nucleic acid detection is unveiled. The target preferences and mismatch specificities of the Cas12j variants are precisely investigated and the optimal Cas12j reaction conditions are determined. As a result, the EXP-J assay for miRNA detection by harnessing the robust trans-cleavage activity of Cas12j on short ssDNA is developed. The EXP-J method demonstrates exceptional detection capabilities for miRNAs, proving that Cas12j can be a pivotal component in molecular diagnostics. Furthermore, the translational potential of the EXP-J assay is validated by detecting oncogenic miRNAs in plasma samples from lung cancer patients. This investigation not only elucidates the trans-cleavage characteristics of Cas12j variants, but also advances the Cas12j-based diagnostic toolkit.

Probiotic bacterial adsorption coupled with CRISPR/Cas12a system for mercury (II) ions detection

The complex sample matrix poses significant challenges in accurately detecting heavy metals. In view of its superior performance for the biological adsorption of heavy metals, probiotic bacteria can be explored for functional unit to eliminate matrix interference. Herein, Lactobacillus rhamnosus (LGG) demonstrates a remarkable tolerance and can adsorb up to 300 μM of Hg2+, following the Freundlich isotherm model with the correlation coefficient (R2) value of 0.9881. Subsequently, by integrating the CRISPR/Cas12a system, a sensitive and specific fluorescent biosensor, "Cas12a-MB," has been developed for Hg2+ detection. Specifically, Hg2+ adsorbed onto LGG can specifically bind to the nucleic acid probe, thereby inhibiting the binding of the probe to LGG and the subsequent activation of the CRISPR/Cas12a system. Under optimal experimental conditions, with the detection time of 90 min and the detection limit of 0.44 nM, the "Cas12a-MB" biosensor offers a novel, eco-friendly approach for Hg2+ detection, showcasing the innovative application of probiotics in biosensor.

Advancing CRISPR-Based Solutions for COVID-19 Diagnosis and Therapeutics

Since the onset of the COVID-19 pandemic, a variety of diagnostic approaches, including RT-qPCR, RAPID, and LFA, have been adopted, with RT-qPCR emerging as the gold standard. However, a significant challenge in COVID-19 diagnostics is the wide range of symptoms presented by patients, necessitating early and accurate diagnosis for effective management. Although RT-qPCR is a precise molecular technique, it is not immune to false-negative results. In contrast, CRISPR-based detection methods for SARS-CoV-2 offer several advantages: they are cost-effective, time-efficient, highly sensitive, and specific, and they do not require sophisticated instruments. These methods also show promise for scalability, enabling diagnostic tests. CRISPR technology can be customized to target any genomic region of interest, making it a versatile tool with applications beyond diagnostics, including therapeutic development. The CRISPR/Cas systems provide precise gene targeting with immense potential for creating next-generation diagnostics and therapeutics. One of the key advantages of CRISPR/Cas-based therapeutics is the ability to perform multiplexing, where different sgRNAs or crRNAs can target multiple sites within the same gene, reducing the likelihood of viral escape mutants. Among the various CRISPR systems, CRISPR/Cas13 and CARVER (Cas13-assisted restriction of viral expression and readout) are particularly promising. These systems can target a broad range of single-stranded RNA viruses, making them suitable for the diagnosis and treatment of various viral diseases, including SARS-CoV-2. However, the efficacy and safety of CRISPR-based therapeutics must be thoroughly evaluated in pre-clinical and clinical settings. While CRISPR biotechnologies have not yet been fully harnessed to control the current COVID-19 pandemic, there is an optimism that the limitations of the CRISPR/Cas system can be overcome soon. This review discusses how CRISPR-based strategies can revolutionize disease diagnosis and therapeutic development, better preparing us for future viral threats.

Poly(vinylpyrrolidone)-Enhanced CRISPR-Cas System for Robust Nucleic Acid Diagnostics

Clustered regularly interspaced short palindromic repeats (CRISPR) technology has opened a new path for molecular diagnostics based on RNA programmed trans-cleavage activity. However, their accessibility for highly sensitive clinical diagnostics remains insufficient. In this study, we systematically investigated the impact of various surfactants on the CRISPR-Cas12a system and found that poly(vinylpyrrolidone) (PVP), a nonionic surfactant, showed the highest enhancement effect among these tested surfactants. Additionally, the enhancement effects of PVP are compatible and versatile to CRISPR-Cas12b and Cas13a systems, improving the sensitivity of these CRISPR-Cas systems toward synthetic targets by 1-2 orders of magnitude. By integrating the PVP-enhanced CRISPR system with isothermal nucleic acid amplification, both the two- and one-step assays exhibited comparable sensitivity and specificity to gold-standard quantitative polymerase chain reaction (qPCR) in the assay of clinical human papillomavirus (HPV) samples, thereby holding significant promise for advancing clinical diagnostics and biomedical research.

CRISPR-based electrochemical biosensors: an alternative for point-of-care diagnostics?

The combination of CRISPR technology and electrochemical sensors has sparked a paradigm shift in the landscape of point-of-care (POC) diagnostics. This review explores the dynamic convergence between CRISPR and electrochemical sensing, elucidating their roles in rapid and precise biosensing platforms. CRISPR, renowned for its remarkable precision in genome editing and programmability capability, has found a novel application in conjunction with electrochemical sensors, promising highly sensitive and specific detection of nucleic acids and biomarkers associated with diverse diseases. This article navigates through fundamental principles, research developments, and applications of CRISPR-based electrochemical sensors, highlighting their potential to revolutionize healthcare accessibility and patient outcomes. In addition, some key points and challenges regarding applying CRISPR-powered electrochemical sensors in real POC settings are presented. By discussing recent advancements and challenges in this interdisciplinary field, this review evaluates the potential of these innovative sensors as an alternative for decentralized, rapid, and accurate POC testing, offering some insights into their applications across clinical scenarios and their impact on the future of diagnostics.

Recombinase Polymerase Amplification and Target-Triggered CRISPR/Cas12a Assay for Sensitive and Selective Hepatitis B Virus DNA Analysis Based on Lanthanide Tagging and Inductively Coupled Plasma Mass Spectrometric Detection

Herein, we report a target-triggered CRISPR/Cas12a assay by coupling lanthanide tagging and inductively coupled plasma mass spectrometry (ICP-MS) for highly sensitive elemental detection. Hepatitis B virus (HBV) DNA was chosen as a model analyte, and recombinase polymerase amplification (RPA) was used for target amplification. The double-stranded RPA amplicons containing a 5' TTTG PAM sequence can be recognized by Cas12a through a specific CRISPR RNA, activating the trans-cleavage activity of CRISPR/Cas12a and nonspecific cleavage of terbium (Tb)-ssDNA modified on magnetic beads (MBs). Following magnetic separation and acid digestion, the released Tb3+ ions were quantitated by ICP-MS and correlated to the concentration of HBV DNA. Taking advantage of the accelerated cleavage of Tb-ssDNA attached to the MB particles, RPA for target amplification, and ICP-MS for highly selective signal readout, this method permits the detection of 1 copy/μL of HBV DNA in serum with high specificity and holds great promise in the early diagnosis of viral infections or tumor development.

Enhanced Two-Step LAMP-CRISPR Assay with an Engineered Zst Polymerase for Contamination-Free and Ultrasensitive DNA Detection

Current loop-mediated isothermal amplification (LAMP)-coupled clustered regularly interspaced short palindromic repeats (LAMP-CRISPR) biosensing in two-step or one-step formats has been applied to next-generation accurate molecular diagnosis. However, two-step LAMP-CRISPR assays intrinsically confront aerosol contamination, while one-step assays possess a compromised detection performance. To this end, we propose an enhanced two-step LAMP-CRISPR assay (ETL-CRISPR) with an engineered Zst polymerase to mediate ultrasensitive DNA detection and thoroughly eliminate aerosol contamination. Instead of supplementing any dTTP, the newly engineered Zst polymerase can efficiently polymerize four oligonucleotides (dATP, dCTP, dGTP, and dUTP), thereby enabling contamination-free and ultrasensitive ETL-CRISPR assay. By targeting the L1 gene of human papillomaviruses (HPV) 16 and the E7 gene of HPV18, our ETL-CRISPR assay achieves high specificity and single-copy level sensitivity within 1 h. Furthermore, we validated the assay by using 85 HPV clinical swab samples with an accuracy of 98.8%, which is comparable to the real-time quantitative polymerase chain reaction. Therefore, ETL-CRISPR provides a straightforward strategy for the contamination-free and ultrasensitive point-of-care diagnosis of clinical pathogens.

Advances in CRISPR-Cas systems for kidney diseases

Recent advances in CRISPR-Cas systems have revolutionised the study and treatment of kidney diseases, including acute kidney injury (AKI), chronic kidney disease (CKD), diabetic kidney disease (DKD), lupus nephritis (LN), and polycystic kidney disease (PKD). CRISPR-Cas technology offers precise and versatile tools for genetic modification in monogenic kidney disorders such as PKD and Alport syndrome. Recent advances in CRISPR technology have also shown promise in addressing other kidney diseases like AKI, CKD, and DKD. CRISPR-Cas holds promise to edit genetic mutations underlying these conditions, potentially leading to more effective and long-lasting treatments. Furthermore, the adaptability of CRISPR-Cas systems allows for developing tailored therapeutic strategies that specifically target the genetic and molecular mechanisms contributing to different kidney diseases. Beyond DNA modifications, CRISPR-Cas technologies also enable editing noncoding RNA, such as lncRNAs and miRNAs, in kidney diseases. Despite these advancements, significant challenges persist, including delivery efficiency to specific kidney cells and potential off-target effects. However, the rapid progress in CRISPR-Cas technology suggests a transformative impact on the future management of kidney diseases, offering the potential for enhanced patient outcomes through personalised and precise therapeutic approaches. This chapter highlights the recent advancement of CRISPR-Cas systems and their potential applications in various kidney diseases.

CRISPR-Based Biosensors for Medical Diagnosis: Readout from Detector-Dependence Detection Toward Naked Eye Detection

The detection of biomarkers (such as DNA, RNA, and protein) plays a vital role in medical diagnosis. The CRISPR-based biosensors utilize the CRISPR/Cas system for biometric recognition of targets and use biosensor strategy to read out biological signals without the employment of professional operations. Consequently, the CRISPR-based biosensors demonstrate great potential for the detection of biomarkers with high sensitivity and specificity. However, the signal readout still relies on specialized detectors, limiting its application in on-site detection for medical diagnosis. In this review, we summarize the principles and advances of the CRISPR-based biosensors with a focus on medical diagnosis. Then, we review the advantages and progress of CRISPR-based naked eye biosensors, which can realize diagnosis without additional detectors for signal readout. Finally, we discuss the challenges and further prospects for the development of CRISPR-based biosensors.

A nanoparticle-assisted signal-enhancement technique for lateral flow immunoassays

Lateral flow immunoassay (LFIA), an affordable and rapid paper-based detection technology, is employed extensively in clinical diagnosis, environmental monitoring, and food safety analysis. The COVID-19 pandemic underscored the validity and adoption of LFIA in performing large-scale clinical and public health testing. The unprecedented demand for prompt diagnostic responses and advances in nanotechnology have fueled the rise of next-generation LFIA technologies. The utilization of nanoparticles to amplify signals represents an innovative approach aimed at augmenting LFIA sensitivity. This review probes the nanoparticle-assisted amplification strategies in LFIA applications to secure low detection limits and expedited response rates. Emphasis is placed on comprehending the correlation between the physicochemical properties of nanoparticles and LFIA performance. Lastly, we shed light on the challenges and opportunities in this prolific field.

Recent Advances in Microfluidics for the Early Detection of Plant Diseases in Vegetables, Fruits, and Grains Caused by Bacteria, Fungi, and Viruses

In the context of global population growth expected in the future, enhancing the agri-food yield is crucial. Plant diseases significantly impact crop production and food security. Modern microfluidics offers a compact and convenient approach for detecting these defects. Although this field is still in its infancy and few comprehensive reviews have explored this topic, practical research has great potential. This paper reviews the principles, materials, and applications of microfluidic technology for detecting plant diseases caused by various pathogens. Its performance in realizing the separation, enrichment, and detection of different pathogens is discussed in depth to shed light on its prospects. With its versatile design, microfluidics has been developed for rapid, sensitive, and low-cost monitoring of plant diseases. Incorporating modules for separation, preconcentration, amplification, and detection enables the early detection of trace amounts of pathogens, enhancing crop security. Coupling with imaging systems, smart and digital devices are increasingly being reported as advanced solutions.

CRISPR/Cas12a-Powered Amplification-Free RNA Diagnostics by Integrating T7 Exonuclease-Assisted Target Recycling and Split G-Quadruplex Catalytic Signal Output

Rapid and sensitive RNA detection is of great value in diverse areas, ranging from biomedical research to clinical diagnostics. Existing methods for RNA detection often rely on reverse transcription (RT) and DNA amplification or involve a time-consuming procedure and poor sensitivity. Herein, we proposed a CRISPR/Cas12a-enabled amplification-free assay for rapid, specific, and sensitive RNA diagnostics. This assay, which we termed T7/G4-CRISPR, involved the use of a T7-powered nucleic acid circuit to convert a single RNA target into numerous DNA activators via toehold-mediated strand displacement reaction and T7 exonuclease-mediated target recycling amplification, followed by activating Cas12a trans-cleavage of the linker strands inhibiting split G-Quadruplex (G4) assembly, thereby inducing fluorescence attenuation proportion to the input RNA target. We first performed step-by-step validation of the entire assay process and optimized the reaction parameters. Using the optimal conditions, T7/G4-CRISPR was capable of detecting as low as 3.6 pM target RNA, obtaining ∼100-fold improvement in sensitivity compared with the most direct Cas12a assays. Meanwhile, its excellent specificity could discriminate single nucleotide variants adjacent to the toehold region and allow species-specific pathogen identification. Furthermore, we applied it for analyzing bacterial 16S rRNA in 40 clinical urine samples, exhibiting a sensitivity of 90% and a specificity of 100% when validated by RT-quantitative PCR. Therefore, we envision that T7/G4-CRISPR will serve as a promising RNA sensing approach to expand the toolbox of CRISPR-based diagnostics.

Highly sensitive detection of aflatoxin B1 byCRISPR/Cas12a-assisted single nanoparticle counting

CRISPR (clustered regularly interspaced short palindromic repeats) and CRISPR-associated protein (Cas) have gained extensive applications in bioassays. However, CRISPR-based detection platforms are often hampered by limited analytical sensitivity, while nucleic acid-based amplification strategies are usually indispensable for additional signal enhancement with potential risks of amplification leakages. To address these challenges, an amplification-free CRISPR-based bioassay of aflatoxin B1 (AFB1) was proposed by applying single nanoparticle counting. Single-particle mode inductively coupled plasma mass spectrometry (Sp-ICPMS) has been regarded as a sensitive tool for nanoparticle counting since one nanoparticle can generate considerable signals above backgrounds. With AFB1, activator strands were introduced to initiate the trans-cleavage of CRISPR/Cas12a for cutting the nanoparticles-tagged-magnetic beads, which were transduced to nanoparticle count signals after separation. Finally, a pico-mole level limit-of-detections (LODs) with moderate selectivity was achieved. Certified reference materials (CRMs) analysis and recovery tests were conducted with promising results. To our best knowledge, this is the first report of the single particle counting-based CRISPR/Cas12a biosensing study.

Rapid and accurate SERS assay of disease-related nucleic acids based on isothermal cascade signal amplifications of CRISPR/Cas13a system and catalytic hairpin assembly

Developing rapid, accurate and convenient nucleic acid diagnostic techniques is essential for the prevention and control of contagious diseases that are prone to gene mutations and may have homologous sequences, especially emerging infectious diseases such as the SARS-CoV-2 pandemic. Herein, a one-pot SERS assay integrating isothermal cascade signal amplification strategy (i.e., CRISPR/Cas13a system (Cas13a) and catalytic hairpin assembly (CHA), Cas13a-CHA) and SERS-active silver nanorods (AgNRs) sensing chips was proposed for rapid and accurate detection of disease-related nucleic acids. Taking SARS-CoV-2 RNA assay as a model, the Cas13a-CHA based SERS sensing strategy can achieve ultra-high sensitivity low to 5.18 × 102 copies·mL-1 within 60 min, and excellent specificity, i.e., not only the ability to identify SARS-CoV-2 RNA from gene mutations, but also incompatibility with coronaviruses such as severe acute respiratory syndrome (SARS-CoV), Middle East respiratory syndrome (MERS-CoV), and other respiratory viruses. The proposed Cas13a-CHA based SERS assay for SARS-CoV-2 RNA has satisfactory sensitivity, specificity, uniformity, and repeatability, and can be easily expanded and universalized for screening different viruses, which is expected to promise as a crucial role for diagnosis of disease-related nucleic acids in various medical application scenarios.

Ultrasensitive protein and exosome analysis based on a rolling circle amplification assisted-CRISPR/Cas12a strategy

CRISPR/Cas12a system has attracted extensive concern in biosensing due to its high specificity and programmability. Nevertheless, existing Cas12a-based assays mainly focus on nucleic acid detection and have limitations in non-nucleic acid biomarker analysis. To broaden the application prospect of the CRISPR/Cas technology, a cascade Cas12a biosensing platform is reported by combining dual-functionalized gold nanoparticles (FGNPs)-assisted rolling circle amplification (RCA) and Cas12a trans-cleavage activity (GAR-Cas) for ultrasensitive protein and exosome analysis. FGNPs serve as a critical component in the transduction of protein or exosome recognition information into nucleic acid amplification events to produce Cas12a activators. In the GAR-Cas assay, by integrating the triple cascade amplification of FGNPs-assisted transduction, RCA, and Cas12a signal amplification, ultralow abundance of target molecules can arouse numerous concatemers to activate Cas12a trans-cleavage activity to release intense fluorescence, allowing the ultrasensitive detection of as low as 1 fg/mL (∼41 aM) cTnI and 5 exosomes per μL. Furthermore, the presented strategy can be applied to detect exosome levels from clinical samples, showing excellent performance in distinguishing cancer patients from healthy individuals. The GAR-Cas sensing platform exhibits great potential in clinical diagnosis and enlarges biosensing toolboxes based on CRISPR/Cas technology for non-nucleic acid target analysis.

Dual CRISPR/Cas13a Cascade Strand Displacement-Triggered Transcription for Point-of-Care Detection of Plasmodium in Asymptomatic Malaria

Asymptomatic infections of Plasmodium parasites are major obstacles to malaria control and elimination. A sensitive, specific, and user-friendly method is urgently needed for point-of-care (POC) Plasmodium diagnostics in asymptomatic malaria, especially in resource-limited settings. In this work, we present a POC method (termed Cas13a-SDT) based on the cascade sequence recognition and signal amplification of dual Cas13a trans-cleavage and strand displacement-triggered transcription (SDT). Cas13a-SDT not only achieves exceptional specificity in discriminating the target RNA from nontarget RNAs with any cross-interaction but also meets the sensitivity criterion set by the World Health Organization (WHO) for effective malaria detection. Remarkably, this novel method was successfully applied to screen malaria in asymptomatic infections from clinical samples. The proposed method provides a user-friendly and visually interpretable output mode while maintaining high accuracy and reliability comparable to RT-PCR. These excellent features demonstrate the significant potential of Cas13a-SDT for POC diagnosis of Plasmodium infections, laying a vital foundation for advancing malaria control and elimination efforts.

A high-fidelity DNAzyme-assisted CRISPR/Cas13a system with single-nucleotide resolved specificity

A CRISPR/Cas system represents an innovative tool for developing a new-generation biosensing and diagnostic strategy. However, the off-target issue (i.e., mistaken cleavage of nucleic acid targets and reporters) remains a great challenge for its practical applications. We hypothesize that this issue can be overcome by taking advantage of the site-specific cleavage ability of RNA-cleaving DNAzymes. To test this idea, we propose a DNAzyme Operation Enhances the Specificity of CRISPR/Cas13a strategy (termed DOES-CRISPR) to overcome the problem of relatively poor specificity that is typical of the traditional CRISPR/Cas13a system. The key to the design is that the partial hybridization of the CRISPR RNA (crRNA) with the cleavage fragment of off-target RNA was not able to activate the collateral cleavage activity of Cas13a. We showed that DOES-CRISPR can significantly improve the specificity of traditional CRISPR/Cas13a-based molecular detection by up to ∼43-fold. The broad utility of the strategy is illustrated through engineering three different systems for the detection of microRNAs (miR-17 and let-7e), CYP2C19*17 gene, SARS-Cov-2 variants (Gamma, Delta, and Omicron) and Omicron subtypes (BQ.1 and XBB.1) with single-nucleotide resolved specificity. Finally, clinical evaluation of this assay using 10 patient blood samples demonstrated a clinical sensitivity of 100% and specificity of 100% for genotyping CYP2C19*17, and analyzing 20 throat swab samples provided a diagnostic sensitivity of 95% and specificity of 100% for Omicron detection, and a clinical sensitivity of 92% and specificity of 100% for XBB.1 detection.

CRISPR-Cas System: A New Dawn to Combat Antibiotic Resistance

Antimicrobial resistance (AMR) can potentially harm global public health. Horizontal gene transfer (HGT), which speeds up the emergence of AMR and increases the burden of drug resistance in mobile genetic elements (MGEs), is the primary method by which AMR genes are transferred across bacterial pathogens. New approaches are urgently needed to halt the spread of bacterial diseases and antibiotic resistance. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), an RNA-guided adaptive immune system, protects prokaryotes from foreign DNA like plasmids and phages. This approach may be essential in limiting horizontal gene transfer and halting the spread of antibiotic resistance. The CRISPR-Cas system has been crucial in identifying and understanding resistance mechanisms and developing novel therapeutic approaches. This review article investigates the CRISPR-Cas system's potential as a tool to combat bacterial AMR. Antibiotic-resistant bacteria can be targeted and eliminated by the CRISPR-Cas system. It has been proven to be an efficient method for removing carbapenem-resistant plasmids and regaining antibiotic susceptibility. The CRISPR-Cas system has enormous potential as a weapon against bacterial AMR. It precisely targets and eliminates antibiotic-resistant bacteria, facilitates resistance mechanism identification, and offers new possibilities in diagnostics and therapeutics.

CRISPR/Cas12a-Amplified Aptamer Switch Microplate Assay for Small Molecules

The presence of small molecule contaminants such as mycotoxins and heavy metals in foods and the environment causes a serious threat to human health and huge economic losses. The development of simple, rapid, sensitive, and on-site methods for small molecule pollutant detection is highly demanded. Here, combining the advantages of structure-switchable aptamer-mediated signal conversion and CRISPR/Cas12a-based signal amplification, we developed a CRISPR/Cas12a-amplified aptamer switch assay on a microplate for sensitive small molecule detection. In this assay, a short DNA strand complementary to the aptamer (cDNA) is immobilized on a microplate, which can capture the aptamer-linked active DNA probe (Apt-acDNA) in the sample solution when the target is absent. With the addition of the Cas12a reporter system, the captured Apt-acDNA probes activate Cas12a to indiscriminately cleave fluorescent DNA substrates, producing a high fluorescence signal. When the target is present, the Apt-acDNA probe specifically binds to the target rather than hybridizing with cDNA on the microplate, and the fluorescence signal is reduced. The analytical performance of our method was demonstrated by the detection of two highly toxic pollutants, aflatoxin B1 (AFB1) and cadmium ion (Cd2+), as examples. The assay exhibited good selectivity and high sensitivity, with detection limits of 31 pM AFB1 and 3.9 nM Cd2+. It also allowed the detection of targets in the actual sample matrix. With the general signal conversion strategy, this method can be used to detect other targets by simply changing the aptamer and cDNA, showing potential practical applications in broad fields.