A universal CRISPR/Cas12a-powered intelligent point-of-care testing platform for multiple small molecules in the healthcare, environment, and food

A smartphone-assisted photoelectrochemical POCT method via Z-scheme CuCo2S4/Fe3O4 for simultaneously detecting co-contamination with microplastics in food and the environment

As emerging contaminants, microplastics threaten food and environmental safety. Dibutyl phthalate (DBP, released from microplastics) and benzo[a]pyrene (BaP, adsorbed on microplastics) coexisted in food and the environment, harming human health, requesting a sensitive and simultaneous testing method to monitor. To address current sensitivity, simultaneousness, and on-site portability challenges during dual targets in complex matrixes, CuCo2S4/Fe3O4 nanoflower was designed to develop a smartphone-assisted photoelectrochemical point-of-care test (PEC POCT). The carrier transfer mechanism in CuCo2S4/Fe3O4 was proven via density functional theory calculation. Under optimal conditions, the PEC POCT showed low detection limits of 0.126, and 0.132 pg/mL, wide linearity of 0.001-500, and 0.0005-50 ng/mL for DBP and BaP, respectively. The smartphone-assisted PEC POCT demonstrated satisfied recoveries (80.00%-119.63%) in real samples. Coherent results were recorded by comparing the PEC POCT to GC-MS (DBP) and HPLC (BaP). This novel method provides a practical platform for simultaneous POCT for food safety and environment monitoring.

Novel Anti-CRISPR-Assisted CRISPR Biosensor for Exclusive Detection of Single-Stranded DNA (ssDNA)

Nucleic acid analysis plays an important role in disease diagnosis and treatment. The discovery of CRISPR technology has provided novel and versatile approaches to the detection of nucleic acids. However, the most widely used CRISPR-Cas12a detection platforms lack the capability to distinguish single-stranded DNA (ssDNA) from double-stranded DNA (dsDNA). To overcome this limitation, we first employed an anti-CRISPR protein (AcrVA1) to develop a novel CRISPR biosensor to detect ssDNA exclusively. In this sensing strategy, AcrVA1 cut CRISPR guide RNA (crRNA) to inhibit the cleavage activity of the CRISPR-Cas12a system. Only ssDNA has the ability to recruit the cleaved crRNA fragment to recover the detection ability of the CRISPR-Cas12 biosensor, but dsDNA cannot accomplish this. By measuring the recovered cleavage activity of the CRISPR-Cas12a biosensor, our developed AcrVA1-assisted CRISPR biosensor is capable of distinguishing ssDNA from dsDNA, providing a simple and reliable method for the detection of ssDNA. Furthermore, we demonstrated our developed AcrVA1-assisted CRISPR biosensor to monitor the enzymatic activity of helicase and screen its inhibitors.

Preparation of a capsaicinoids broad spectrum antibody and its application in non-enzyme immunoassay based on DMSNs@PDA@Pt

Capsaicinoids (CPCs) is a special ingredient with pungent smell in condiments, which can also be used as an exogenetic marker for kitchen waste oil. Development of immunoassay for CPCs remains a challenging due to relatively difficult preparation of the broad-spectrum antibody (Ab). In this work, a broad-spectrum polyclonal antibody (pAb) which can simultaneously recognize capsaicin (CPC), dihydrocapsaicin (DCPC), nordihydrocapsaicin (NDCPC), and N-vanillylnonanamide (N-V) is produced, and a non-enzyme immunoassay (NISA) based on this Ab, dendritic mesoporous silica nanomaterials (DMSNs), polydopamine (PDA), and high catalytic efficiency of Pt nanoparticles to prepare signal probe (DMSNs@PDA@Pt) is established. Here, the limit of detection (LOD) of NISA for CPC is as low as 0.04 μg L-1. It is worth mentioning that the LOD of the proposed NISA is at least 23 times lower than that of traditional enzyme-linked immunosorbent assay (ELISA) based on horseradish peroxidase (HRP). Moreover, the proposed NISA is applied to detect CPCs in edible oil samples, the result has good consistency with that of ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The proposed NISA based on DMSN@PDA@Pt and broad-spectrum Ab is an ideal tool for highly effective screening CPCs for kitchen waste oil abuse surveillance.

A multiplex RPA coupled with CRISPR-Cas12a system for rapid and cost-effective identification of carbapenem-resistant Acinetobacter baumannii

Background

Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a severe nosocomial threat, prompting a need for efficient detection methods. Traditional approaches, such as bacterial culture and PCR, are time-consuming and cumbersome. The CRISPR-based gene editing system offered a potential approach for point-of-care testing of CRAB.

Methods

We integrated recombinase polymerase amplification (RPA) and CRISPR-Cas12a system to swiftly diagnose CRAB-associated genes, OXA-51 and OXA-23. This multiplex RPA-CRISPR-Cas12a system eliminates bulky instruments, ensuring a simplified UV lamp-based outcome interpretation.

Results

Operating at 37°C to 40°C, the entire process achieves CRAB diagnosis within 90 minutes. Detection limits for OXA-51 and OXA-23 genes are 1.3 × 10-6 ng/μL, exhibiting exclusive CRAB detection without cross-reactivity to common pathogens. Notably, the platform shows 100% concordance with PCR when testing 30 clinical Acinetobacter baumannii strains.

Conclusion

In conclusion, our multiplex RPA coupled with the CRISPR-Cas12a system provides a fast and sensitive CRAB detection method, overcoming limitations of traditional approaches and holding promise for efficient point-of-care testing.

A novel universal small-molecule detection platform based on antibody-controlled Cas12a switching

Molecular diagnostics play an important role in illness detection, prevention, and treatment, and are vital in point-of-care test. In this investigation, a novel CRISPR/Cas12a based small-molecule detection platform was developed using Antibody-Controlled Cas12a Biosensor (ACCBOR), in which antibody would control the trans-cleavage activity of CRISPR/Cas12a. In this system, small-molecule was labeled around the PAM sites of no target sequence(NTS), and antibody would bind on the labeled molecule to prevent the combination of CRISPR/Cas12a, resulting the decrease of trans-cleavage activity. Biotin-, digoxin-, 25-hydroxyvitamin D3 (25-OH-VD3)-labeled NTS and corresponding binding protein were separately used to verify its preformance, showing great universality. Finally, one-pot detection of 25-OH-VD3 was developed, exhibiting high sensitivity and excellent specificity. The limit of detection could be 259.86 pg/mL in serum within 30 min. This assay platform also has the advantages of low cost, easy operation (one-pot method), and fast detection (∼30 min), would be a new possibilities for the highly sensitive detection of other small-molecule targets.

Ultrasensitive ImmunoMag-CRISPR Lateral Flow Assay for Point-of-Care Testing of Urinary Biomarkers

Rapid, accurate, and noninvasive detection of biomarkers in saliva, urine, or nasal fluid is essential for the identification, early diagnosis, and monitoring of cancer, organ failure, transplant rejection, vascular diseases, autoimmune disorders, and infectious diseases. We report the development of an Immuno-CRISPR-based lateral flow assay (LFA) using antibody-DNA barcode complexes with magnetic enrichment of the target urinary biomarkers CXCL9 and CXCL10 for naked eye detection (ImmunoMag-CRISPR LFA). An intermediate approach involving a magnetic bead-based Immuno-CRISPR assay (ImmunoMag-CRISPR) resulted in a limit of detection (LOD) of 0.6 pg/mL for CXCL9. This value surpasses the detection limits achieved by previously reported assays. The highly sensitive detection method was then re-engineered into an LFA format with an LOD of 18 pg/mL for CXCL9, thereby enabling noninvasive early detection of acute kidney transplant rejection. The ImmunoMag-CRISPR LFA was tested on 42 clinical urine samples from kidney transplant recipients, and the assay could determine 11 positive and 31 negative urinary samples through a simple visual comparison of the test line and the control line of the LFA strip. The LFA system was then expanded to quantify the CXCL9 and CXCL10 levels in clinical urine samples from images. This approach has the potential to be extended to a wide range of point-of-care tests for highly sensitive biomarker detection.

Sensitive and Portable Signal Readout Strategies Boost Point-of-Care CRISPR/Cas12a Biosensors

Point-of-care (POC) detection is getting more and more attention in many fields due to its accuracy and on-site test property. The CRISPR/Cas12a system is endowed with excellent sensitivity, target identification specificity, and signal amplification ability in biosensing because of its unique trans-cleavage ability. As a result, a lot of research has been made to develop CRISPR/Cas12a-based biosensors. In this review, we focused on signal readout strategies and summarized recent sensitivity-improving strategies in fluorescence, colorimetric, and electrochemical signaling. Then we introduced novel portability-improving strategies based on lateral flow assays (LFAs), microfluidic chips, simplified instruments, and one-pot design. In the end, we also provide our outlook for the future development of CRISPR/Cas12a biosensors.

Enhanced detection of Listeria monocytogenes using tetraethylenepentamine-functionalized magnetic nanoparticles and LAMP-CRISPR/Cas12a-based biosensor

BACKGROUND

Listeria monocytogenes is a pathogenic bacterium that can lead to severe illnesses, especially among vulnerable populations. Therefore, the development of rapid and sensitive detection methods is vital to prevent and manage foodborne diseases. In this study, we used tetraethylenepentamine (TEPA)-functionalized magnetic nanoparticles (MNPs) and a loop-mediated isothermal amplification (LAMP)-based CRISPR/Cas12a-based biosensor to concentrate and detect, respectively, L. monocytogenes. LAMP enables DNA amplification at a constant temperature, providing a highly suitable approach for point-of-care testing (POCT). The ability of CRISPR/Cas12a to cleave ssDNA reporter, coupled with TEPA-functionalized MNPs effective attachment to negatively charged bacteria, forms a promising biosensor.

RESULTS

The LAMP assay was meticulously developed by selecting specific primers and designing crRNA sequences targeting a specific region within the hly gene of L. monocytogenes. We selected primer and refined the amplification conditions by systematically exploring a temperature range from 59 °C to 69 °C, ensuring the attainment of optimal performance. This process was complemented by systematic optimization of LAMP-CRISPR/Cas12a system parameters. In particular, we successfully established the optimal ssDNA reporter concentrations (0-1.2 μM) and Cas12a-mediated trans-cleavage times (0-20 min), crucial components that underpin the effectiveness of the LAMP-CRISPR/Cas12a-based biosensor. For optimizing parameters in capturing L. monocytogenes using TEPA-functionalized MNPs, capture efficiency was significantly enhanced through adjustments in TEPA-functionalized MNPs concentration, incubation times, and magnetic separation duration. Large-volume (20 mL) magnetic separation exhibited a 10-fold sensitivity improvement over conventional methods. Utilizing TEPA-functionalized MNPs, the LAMP-CRISPR/Cas12a-based biosensor achieved detection limits of 100 CFU mL-1 in pure cultures and 100 CFU g-1 in enoki mushrooms.

SIGNIFICANCE

The integration of this novel technique with the LAMP-CRISPR/Cas12a-based biosensor enhances the accuracy and sensitivity of L. monocytogenes detection in foods, and it can be a promising biosensor for POCT. The 10-fold increase in sensitivity compared to conventional methods makes this approach a groundbreaking advancement in pathogenic bacteria detection for food safety and public health.

CRISPR-based diagnostics of different biomolecules from nucleic acids, proteins, and small molecules to exosomes

CRISPR-based detection technologies have been widely explored for molecular diagnostics. However, the challenge lies in converting the signal of different biomolecules, such as nucleic acids, proteins, small molecules, exosomes, and ions, into a CRISPR-based nucleic acid detection signal. Understanding the detection of different biomolecules using CRISPR technology can aid in the development of practical and promising detection approaches. Unfortunately, existing reviews rarely provide an overview of CRISPR-based molecular diagnostics from the perspective of different biomolecules. Herein, we first introduce the principles and characteristics of various CRISPR nucleases for molecular diagnostics. Then, we focus on summarizing and evaluating the latest advancements in CRISPR-based detection of different biomolecules. Through a comparison of different methods of amplification and signal readout, we discuss how general detection methods can be integrated with CRISPR. Finally, we conclude by identifying opportunities for the improvement of CRISPR in quantitative, amplification-free, multiplex, all-in-one, and point-of-care testing (POCT) purposes.

CRISPR/Cas System: The Accelerator for the Development of Non-nucleic Acid Target Detection in Food Safety

Non-nucleic acid targets have posed a serious challenge to food safety. The detection of non-nucleic acid targets can enable us to monitor food contamination in a timely manner. In recent years, the CRISPR/Cas system has been extensively explored in biosensing. However, there is a lack of a summary of CRISPR/Cas-powered detection tailored to non-nucleic acid targets involved in food safety. This review comprehensively summarizes the recent advances on the construction of CRISPR/Cas-powered detection and the promising applications in the field of food safety related non-nucleic acid targets. The current challenges and futuristic perspectives are also proposed accordingly. The rapidly evolving CRISPR/Cas system has provided a powerful propellant for non-nucleic acid target detection via integration with aptamer and/or DNAzyme. Compared with traditional analytical methods, CRISPR/Cas-powered detection is conceptually novel, essentially eliminates the dependence on large instruments, and also demonstrates the capability for rapid, accurate, sensitive, and on-site testing.