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Therapeutics based on clustered regularly interspaced short palindromic repeats (CRISPR) have gained significant attention as a promising synthetic biology technique, but there are concerns about the potential for persistent activation of CRISPR-associated protein (Cas) and subsequent off-target effects. This forum focuses on advances in anti-CRISPR studies based on non-protein substances in the hope of developing effective anti-CRISPR strategies to mitigate these concerns. [ABSTRACT FROM AUTHOR]

Cadmium ion (Cd(II)) is a pernicious environmental pollutant that has been shown to contaminate agricultural lands, accumulate through the food chain, and seriously threaten human health. At present, Cd(II) monitoring is dependent on centralized instruments, necessitating the development of rapid and on-site detection platforms. Against this backdrop, the present study reports on the development of a fluorometric aptasensor designed to target Cd(II), which is achieved through the integration of strand displacement amplification (SDA) and CRISPR/Cas12a. In the absence of Cd(II), the aptamer initiates SDA, resulting in the generation of a profusion of ssDNA that activates Cas12a, leading to a substantial increase in fluorescence output. Conversely, the presence of Cd(II) curtails the SDA efficiency, culminating in a significant reduction in fluorescence output. The proposed approach has been demonstrated to enable the selective detection of Cd(II) at concentrations of 60 pM, with the performance of the aptasensor validated in real water and rice samples. The proposed platform based on aptamer-target interaction holds immense promise as a signal-amplified and precise method for the detection of Cd(II) and has the potential to transform current hazard detection practices in food samples. [ABSTRACT FROM AUTHOR]

Transcription factors (TFs) are critical proteins that regulate the expression of genes, and the abnormal change of TFs levels is directly related to physical dysfunctions. Herein, we developed a clustered regularly interspaced short palindromic repeats (CRISPR)-based biosensor for the measurement of TFs level with the assistance of exonuclease protection assay. A dsDNA (activator) with the ability to activate Cas12a was engineered to contain TFs binding domain, and the binding between TFs and the activator can protect the dsDNA from being digested by exonuclease III (Exo III). The reserved activator then triggered a CRISPR/Cas12a reporting reaction to produce fluorescent signal for detection. In the detection of nuclear factor-kappa B (NF-κB) p50 subunit, the limit of detection of 0.2 pM and limit of quantification of 0.6 pM were obtained respectively, and the performance of this biosensor has been challenged by cell nucleoprotein extracts. Additionally, this method can be applied in the screening and evaluation of TFs inhibitors, calculating the IC50 of oridonin. Integrating merits including high sensitivity, low cost, and good portability, this method may enrich the arsenal for TFs-related applications. [Display omitted] • A CRISPR/Cas12a-based biosensor targeting TFs was developed. • Exonuclease protection and Cas12a were integrated for TFs sensing. • Convenient detection of NF-κB p50 with LOD of 0.2 pM was realized. • This sensor can be applied in the screening and evaluation of TFs inhibitors. [ABSTRACT FROM AUTHOR]

Transcription factors (TFs) are the key proteins for the decision of cell fates, and they have been recognized as potent markers for diagnostic and treatment of diseases. Herein, we report on a highly sensitive biosensor for the detection of TFs based on the CRISPR/Cas12a system. This biosensor was accomplished based on the competitive binding of the Cas12a-crRNA and TFs towards a dsDNA referred to as activator. Without TFs, the activator can be recognized by Cas12a-crRNA and cause the activation of the DNase activity of Cas12a. When TFs were added, the TFs can bind with the activator because the activator was designed to contain the specific binding sites of target TFs. We find that this binding can inhibit the association between Cas12a-crRNA and the activator, which hinders the activation of Cas12a. As a proof-of-concept, the rapid detection of five kinds of TFs was presented, and the detection was extended to the analysis of TFs expression in xenograft solid tumors from mice. This investigation is the first attempt to apply CRISPR technology in the sensing of TFs, and it discloses that the blocking of activator can be applied as a new sensing mechanism for the development of CRISPR-based biosensor. • It is found that TFs can compete and inhibit the dsDNA-induced activation of Cas12a. • CRISPR technology is first applied in the biosensing of transcription factors. • The inhibition-based sensing mechanism for CRISPR is proposed. • Rapid sensing of multiple TFs with picomolar sensitivity is realized. [ABSTRACT FROM AUTHOR]

High mannose is overexpressed on the cell surface during carcinogenesis; however, there are currently no efficient techniques for its detection. Herein, we propose an assay called RADAR (r emote high m a nnose d etection on cell surf a ce with C R ISPR) for the quantification of high mannose, leveraging the integration of high mannose-binding aptamer and CRISPR technique. The high mannose-binding aptamer is hybridized with a locker, which is released upon specific binding to high mannose. The released locker then activates CRISPR/Cas12a to produce a fluorescence signal. The "remote" concept in RADAR refers to the recognition of high mannose occurring on the cell surface, while signal generation takes place in a solution separate from the target. This feature makes RADAR suitable for the detection of suspended bio-samples without the need for sophisticated imaging. RADAR can detect high mannose Man 9 with a limit of detection of 2.5 nM, distinguish cancer cells from non-cancerous cells, and profile high mannose level in human serum for potential non-small cell lung cancer (NSCLC) diagnosis. This work represents the first attempt to integrate CRISPR technology into the aptasensing of high mannose, which may serve as a synthetic biology-enabled tool in glycochemistry and glycobiology. • CRISPR/Cas12a was first applied in the detection of cell surface high mannose. • High mannose aptamer was applied in biosensing for the first time. • This assay is suitable for the detection of bio-samples without sophisticated imaging. [ABSTRACT FROM AUTHOR]

CRISPR/Cas12a-based biosensors typically output fluorescent, colorimetric, and electrochemical signals, relying on reporters that suffer from low sensitivity, high cost, and low stability. Herein, we introduced a label-free chemiluminescent (CL) reporting system based on a DNAzyme known as "Supernova". Supernova catalyzes the translocation of phosphate from a 1,2-dioxetane substrate (specifically, CDP-Star) to its 5′-OH ends, thereby triggering a CL reaction that produces light. Upon activation by the target, Cas12a cleaves Supernova, rendering it inactive in reacting with CDP-Star. Without pre-amplification, this biosensor can detect synthetic DNA corresponding to the SARS-CoV-2 N gene and monkeypox virus (MPXV) F3L gene with detection limits (LOD) of 1.5 and 2.4 pM, respectively. Integration with pre-amplification further enables the detection of SARS-CoV-2 and MPXV genes down to 1 copy/μL in real samples. Furthermore, the application of this CL system was expanded to the detection of non-nucleic acids with the integration of ATP aptamers, resulting in improved sensitivity in ATP biosensing compared to fluorescent assays. Overall, this work represents the first development of a label-free CL Cas12a reporting system, demonstrating its enhanced performance and broad applicability in synthetic biology-enabled sensing technology. • Label-free chemiluminescence Cas12a reporting system was developed. • DNAzyme Supernova was applied in biosensing for the first time. • This system shows high universality for nucleic acids and non-nucleic acids detection. [ABSTRACT FROM AUTHOR]

CRISPR is reshaping biosensing technology due to its programmability, sensitivity, and specificity. Most current CRISPR-based biosensors are developed based on Cas12 and Cas13, while the biosensing potentials of the newly discovered Cas14 have not been fully elucidated yet. Herein, a fluorometric biosensor named HARRY (h ighly sensitive a ptamer- r egulated Cas14 R -loop for bioanal y sis) was developed. The diblock ssDNA is designed to contain the activator sequence of Cas14 and the aptamer sequence of specific targets. In the absence of targets, the ssDNA activates Cas14a, then the Cas14a trans -cleavages the fluorescent reporter, causing fluorescence enhancement. In the presence of the targets, ssDNA-target assembly is formed via aptamer interaction, resulting in the inhibition of Cas14a activation. HARRY can detect ATP, Cd2+, histamine, aflatoxin B1, and thrombin with detection limits at the low-nanomolar level, which shows improvement compared with Cas12a-based aptasensors in sensitivity and versatility. We reasoned that the improvement is derived from the ssDNA specificity of Cas14a and found that the detection limit of HARRY is correlated to the binding affinities of aptamers. This study unlocks the potential of Cas14a in versatile aptasensing, which may inspire the development of CRISPR-based biosensors from the Cas14a branch. [Display omitted] • A fluorometric aptasensor based on CRISPR/Cas14 was developed. • This Cas14-based aptasensor is sensitive in the detection of diverse targets. • Cas14 is more sensitive than Cas12 in aptasensing. [ABSTRACT FROM AUTHOR]

The pathogen Enterocytozoon hepatopenaei (EHP) has significantly affected the shrimp farming industry since the last decade. For effective prevention, accurate and reliable detection methods for EHP infection are important, especially the methods suitable for point-of-care testing (POCT) environment. By combining recombinase polymerase amplification (RPA) with the CRISPR-Cas12a system, this study developed a POCT-friendly detection method for EHP infection with one-pot procedure. The combined method utilized robust amplification capacity of RPA and high specificity of CRISPR, thus had better accuracy and reliability. The one-pot procedure was achieved by careful design and screening of the crRNA and systematic optimization of the reaction. The issues related to the compatibility of RPA and Cas12a cleavage have been successfully solved. The method was highly specific and the sensitivity reached 101 gene copies per reaction. The practical performance was validated with clinical shrimp samples. With the generous temperature requirement and convenient end-point reading of results, the one-pot method is highly suitable for POCT environment. It is a good example of one-pot RPA-CRISPR detection assay for POCT purpose, and has great application value in prevention of EHP infection in shrimp farming industry. • A novel molecular detection method for Enterocytozoon hepatopenaei. • A POCT-friendly, RPA and CRISPR combined method with one-pot procedure. • Issues related to the compatibility of RPA and CRISPR successfully solved. • A good example of one-pot RPA-CRISPR detection assay for POCT purpose. [ABSTRACT FROM AUTHOR]

Protamine, an arginine-rich polycationic peptide, is a natural food preservative and the only approved antidote to heparin overdose. The detection of protamine is meaningful; however, the detection of protamine is difficult due to the lack of aromatic amino acids in its composition. Herein, we proposed a fluorometric biosensor for the sensitive detection of protamine based on the protamine-mediated regulation of CRISPR/Cas12a collateral cleavage. In the absence of protamine, the DNA probe specifically hybridizes with the Cas12a-crRNA complex, causing the activation of Cas12a. In the presence of protamine, positively charged protamine tightly binds to negatively charged DNA probes through electrostatic interaction, so that the DNA probe cannot hybridize with the Cas12a-crRNA complex. Using a short ssDNA modified with fluorophore and quencher as a reporter, the information of protamine concentration is transduced into DNA information and sensed in a signal turn-off manner. The linear range of this method in protamine detection is 0.04–3.2 μg/mL, yielding a detection limit of 0.03 μg/mL, and the entire sampling-to-response time is about 1 h. This biosensor provides a rationale for using the programmable nuclease Cas12a to detect protamine, and further advances the application of CRISPR technology in bioanalyses. • The inhibitory effect of protamine on CRISPR/Cas12a activity was reported. • The affinity of protamine-ssDNA binding is higher than that between ssDNA and Cas12a-crRNA. • Highly sensitive and selective protamine detection was realized. [ABSTRACT FROM AUTHOR]

CRISPR/Cas machinery has revolutionized the analytical platform for the precise detection of diverse analytes. Specific target recognition and robust signal transduction are crucial requirements for a superior sensing platform. The signal generation is directly related to the reporter traits in CRISPR/Cas systems. This review illustrated reporter engineering and its significance in improving the CRISPR/Cas-based detection platform. It is the first review highlighting the role of reporter elements, the nucleic acid sequence and transducer, for multiplexing and discriminate detection of targets. We described the significance of the reporters, the role of Cas ribonucleoproteins and their specific reporters, reporter nucleic acid and transducer engineering and their impact on multiplexing and target differentiation, working principles of reporters, demerits of CRISPR technology, and upcoming investigation. We envision that this review will be a milestone in fabricating the CRISPR/Cas reporters and discriminate multiplexed sensors for applications on a commercial scale. • The critical roles of reporters in CRISPR/Cas-based bioassays are specified. • The design principles of CRISPR/Cas reporters are discussed. • The strategies for reporter engineering are described. • The limitations of current reporters and perspectives of future horizons are critically discussed. [ABSTRACT FROM AUTHOR]

The CRISPR/Cas technology, derived from an adaptive immune system in bacteria, has been awarded the Nobel Prize in Chemistry in 2020 for its success in gene editing. Increasing reports reveal that CRISPR/Cas technology has a wide scope of applications and it could be incorporated into biosensors for detecting critical analytes. CRISPR-powered biosensors have attracted significant research interest due to their advantages including high accuracy, good specificity, rapid response, and superior integrity. Now the CRISPR technology is not only admirable in nucleic acid monitoring, but also promising for other kinds of biomarkers' detection, including metal ions, small molecules, peptides, and proteins. Therefore, it is of great worth to explore the prospect, and summarize the strategies in applying CRISPR technology for the recognition of a broad range of targets. In this review, we summarized the strategies of CRISPR biosensing for non-nucleic-acid analytes, the latest development of nucleic acid detection, and proposed the challenges and outlook of CRISPR-powered biosensors. • The breakthrough achievements of CRISPR biosensors in non-nucleic acid detection are summarized. • The latest development of CRISPR biosensors in nucleic acid detection was introduced. • The challenges and prospects of CRISPR biosensors are described. • The chemical fundamental of the commonly used Cas enzyme was mentioned. [ABSTRACT FROM AUTHOR]