CHO cell engineering via targeted integration of circular miR-21 decoy using CRISPR/RMCE hybrid system.

Chinese hamster ovary (CHO) cells, widely acknowledged as the preferred host system for industrial recombinant protein manufacturing, play a crucial role in developing pharmaceuticals, including anticancer therapeutics. Nevertheless, mammalian cell-based biopharmaceutical production methods are still beset by cellular constraints such as limited growth and poor productivity. MicroRNA-21 (miR-21) has a major impact on a variety of malignancies, including glioblastoma multiforme (GBM). However, reduced productivity and growth rate have been linked to miR-21 overexpression in CHO cells. The current study aimed to engineer a recombinant CHO (rCHO) cell using the CRISPR-mediated precise integration into target chromosome (CRIS-PITCh) system coupled with the Bxb1 recombinase-mediated cassette exchange (RMCE) to express a circular miR-21 decoy (CM21D) with five bulged binding sites for miR-21 sponging. Implementing the ribonucleoprotein (RNP) delivery method, a landing pad was inserted into the genome utilizing the CRIS-PITCh technique. Subsequently, the CM21D cassette flanked by Bxb1 attB was then retargeted into the integrated landing pad using the RMCE/Bxb1 system. This strategy raised the targeting efficiency by 1.7-fold, and off-target effects were decreased. The miR-21 target genes (Pdcd4 and Atp11b) noticed a significant increase in expression upon the miR-21 sponging through CM21D. Following the expression of CM21D, rCHO cells showed a substantial decrease in doubling time and a 1.3-fold increase in growth rate. Further analysis showed an increased yield of hrsACE2, a secretory recombinant protein, by 2.06-fold. Hence, we can conclude that sponging-induced inhibition of miR-21 may lead to a growth rate increase that could be linked to increased CHO cell productivity. For industrial cell lines, including CHO cells, an increase in productivity is crucial. The results of our research indicate that CM21D is an auspicious CHO engineering approach. KEY POINTS: • CHO is an ideal host cell line for producing industrial therapeutics manufacturing, and miR-21 is downregulated in CHO cells, which produce recombinant proteins. • The miR-21 target genes noticed a significant increase in expression upon the miR-21 sponging through CM21D. Additionally, sponging of miR-21 by CM21D enhanced the growth rate of CHO cells. • Productivity and growth rate were increased in CHO cells expressing recombinant hrs-ACE2 protein after CM21D knocking in.

Development of recombinase amplification assays for the rapid detection of infectious myonecrosis virus.

Infectious myonecrosis virus (IMNV) has affected shrimp farming in many countries, such as northeastern Brazil and southeast Asia, and poses a serious threat to the global shrimp industry. Reverse transcription enzymatic recombinant amplification technology (RT-ERA) is a rapid DNA amplification assay with high specificity in isothermal conditions and has been widely applied to the pathogen's detection. In this study, two novel ERA assays of IMNV, real-time RT-ERA and an RT-ERA combined with lateral flow dipsticks assay (RT-ERA-LFD), were developed and evaluated. The real-time RT-ERA assay could be carried out at 38-42 °C and had the highest end-point fluorescence value and the smallest Ct value at 41 °C. The brightness and width of the detection line were at a maximum at 39 °C and 30 min, and these conditions were selected in RT-ERA-LFD. Both real-time RT-ERA and RT-ERA-LFD produced positive results with IMNV standard plasmids only and showed no cross-reaction with Vibrio parahaemolyticus, which causes acute hepatopancreatic necrosis disease (VpAHPND); white spot syndrome virus (WSSV); infectious hypodermal and hematopoietic necrosis virus (IHHNV); or Ecytonucleospora hepatopenaei (EHP). Meanwhile, we compared the sensitivities of nested RT-PCR, real-time RT-PCR, real-time RT-ERA, and RT-ERA-LFD. The sensitivities of real-time RT-ERA and RT-ERA-LFD were both 101 copies/µL. The detection sensitivities of nested RT-PCR and real-time RT-PCR were 100 and 102 copies/µL, respectively. As a result, two ERA assays were determined to be specific, sensitive, and economical methods for the on-site diagnosis of IMNV infection, showing great potential for the control of IMNV infections.

Rapid and multi-target genotyping of Helicobacter pylori with digital microfluidics.

Helicobacter pylori (H. pylori) infection correlates closely with gastric diseases such as gastritis, ulcers, and cancer, influencing more than half of the world's population. Establishing a rapid, precise, and automated platform for H. pylori diagnosis is an urgent clinical need and would significantly benefit therapeutic intervention. Recombinase polymerase amplification (RPA)-CRISPR recently emerged as a promising molecular diagnostic assay due to its rapid detection capability, high specificity, and mild reaction conditions. In this work, we adapted the RPA-CRISPR assay on a digital microfluidics (DMF) system for automated H. pylori detection and genotyping. The system can achieve multi-target parallel detection of H. pylori nucleotide conservative genes (ureB) and virulence genes (cagA and vacA) across different samples within 30 min, exhibiting a detection limit of 10 copies/rxn and no false positives. We further conducted tests on 80 clinical saliva samples and compared the results with those derived from real-time quantitative polymerase chain reaction, demonstrating 100% diagnostic sensitivity and specificity for the RPA-CRISPR/DMF method. By automating the assay process on a single chip, the DMF system can significantly reduce the usage of reagents and samples, minimize the cross-contamination effect, and shorten the reaction time, with the additional benefit of losing the chance of experiment failure/inconsistency due to manual operations. The DMF system together with the RPA-CRISPR assay can be used for early detection and genotyping of H. pylori with high sensitivity and specificity, and has the potential to become a universal molecular diagnostic platform.

Real-time MBDi-RPA using methyl-CpG binding protein 2: A real-time detection method for simple and rapid estimation of CpG methylation status.

BACKGROUND: Analysis of CpG methylation is informative for cancer diagnosis. Previously, we developed a novel method to discriminate CpG methylation status in target DNA by blocking recombinase polymerase amplification (RPA), an isothermal DNA amplification technique, using methyl-CpG binding domain (MBD) protein 2 (MBD2). The method was named MBD protein interference-RPA (MBDi-RPA). In this study, MBDi-RPA was performed using methyl-CpG binding protein 2 (MeCP2), another MBD family protein, as the blocking agent. RESULTS: MBDi-RPA using MeCP2 detected low levels of CpG methylation, showing that it had higher sensitivity than MBDi-RPA using MBD2. We also developed real-time RPA, which enabled rapid analysis of DNA amplification without the need for laborious agarose gel electrophoresis and used it in combination with MBDi-RPA. We termed this method real-time MBDi-RPA. The method using MeCP2 could determine the abundance ratio of CpG-methylated target DNA simply and rapidly, although highly sensitive detection was challenging. SIGNIFICANCE AND NOVELTY: Real-time MBDi-RPA using MeCP2 could be potentially useful for estimating CpG methylation status in target DNA prior to more detailed analyses.

Extraction-free, immuno-RPA-CRISPR/Cas13a-based one-pot detection of glypican-3 directly from extracellular vesicles.

BACKGROUND: Glypican-3 (GPC3) is a heparan sulfate proteoglycan (HSPG) that binds to the cell membrane via glycosylphosphatidylinositol (GPI). It is not found in healthy adult liver but is overexpressed in human hepatocellular carcinoma (HCC). The protein marker GPC3 on extracellular vesicles (GPC3+ EVs) is also useful for HCC detection. Nevertheless, the absence of practical and dependable quantitative techniques to evaluate EVs proteins prevents their clinical implementation. RESULTS: Here, using an immuno-recombinase polymerase amplification (immuno-RPA) process and dual amplification of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas13a, we firstly create an extraction-free one-pot immuno-RPA-CRISPR (opiCRISPR) for the direct and extremely sensitive detection of EVs proteins. The EVs protein-targeted detection probe is amplified by RPA to generate a long repetitive sequence containing multiple CRISPR RNA (crRNA) targeting barcodes, and the signal is further amplified by the CRISPR-Cas13a side-chain cleavage activity to generate a fluorescent signal. The results show that circulating extracellular vesicle GPC3 (eGPC3) levels are a reliable marker for GPC3 expression in tumor, opening up new avenues for tumor diagnosis. SIGNIFICANCE AND NOVELTY: We created an eGPC3 assay based on the CRISPR-Cas13a system, and successfully study the significance of extracellular vesicle GPC3 markers in hepatocellular carcinoma.

Purification and biochemical characterization of the G4 resolvase and DNA helicase FANCJ.

G-quadruplex (G4) DNA or RNA poses a unique nucleic acid structure in genomic transactions. Because of the unique topology presented by G4, cells have exquisite mechanisms and pathways to metabolize G4 that arise in guanine-rich regions of the genome such as telomeres, promoter regions, ribosomal DNA, and other chromosomal elements. G4 resolvases are often represented by a class of molecular motors known as helicases that disrupt the Hoogsteen hydrogen bonds in G4 by harnessing the chemical energy of nucleoside triphosphate hydrolysis. Of special interest to researchers in the field, including us, is the human FANCJ DNA helicase that efficiently resolves G4 DNA structures. Notably, FANCJ mutations are linked to Fanconi Anemia and are prominent in breast and ovarian cancer. Since our discovery that FANCJ efficiently resolves G4 DNA structures 15 years ago, we and other labs have characterized mechanistic aspects of FANCJ-catalyzed G4 resolution and its biological importance in genomic integrity and cellular DNA replication. In addition to its G4 resolvase function, FANCJ is also a classic DNA helicase that acts on conventional duplex DNA structures, which are relevant to the enzyme's role in interstrand cross link repair, double-strand break repair via homologous recombination, and response to replication stress. Here, we describe detailed procedures for the purification of recombinant FANCJ protein and characterization of its G4 resolvase and duplex DNA helicase activity.

Combining recombinase polymerase amplification with tyrosine modified 2'-deoxyuridine-5'-triphosphate for direct voltammetric detection of double-stranded DNA: Application to potato pathogen Dickeya solani.

The approach based on a combination of isothermal recombinase polymerase amplification (RPA), 2'-deoxyuridine-5'-triphosphate modified with tyrosine aromatic group (dUTP-Y1), and direct voltammetric detection of RPA product carrying electroactive labels was successfully applied to the potato pathogen Dickeya solani. The artificial nucleotide dUTP-Y1 demonstrated a good compatibility with RPA, enabling by targeting a section of D. solani genome with a unique sequence to produce the full-size modified products at high levels of substitution of dTTP by dUTP-Y1 (up to 80-90 %) in the reaction mixture. The optimized procedure of square wave voltammetry allowed to reliably detect the product generated by RPA at 80 % substitution of dTTP by dUTP-Y1 (dsDNA-Y1) in microliter sample volumes on the surface of disposable carbon screen printed electrodes at the potential of about 0.6 V. The calibration curve for the amplicon detection was linear in coordinates 'Ip, A vs. Log (c, M)' within the 0.05-1 µM concentration range. The limit of detection for dsDNA-Y1 was estimated as 8 nM. The sensitivity of the established electrochemical approach allowed to detect amplicons generated in a single standard 50 µL RPA reaction after their purification with silica-coated magnetic beads. The overall detectability of D. solani with the suggested combination of RPA and voltammetric registration of dsDNA-Y1 can be as low as a few copies of bacterial genome per standard reaction. In total, amplification, purification, and electrochemical detection take about 120-150 min. Considering the potential of direct electrochemical analysis for miniaturization, as well as compliance with low-cost and low-power requirements, the findings provide grounds for future development of microfluidic devices integrating isothermal amplification, amplicon purification and detection based on the tyrosine modified nucleotide for the purpose of 'on-site' detection of various pathogens.

Dual-RPA assay for rapid detection and differentiation of E.granulosus and E.multilocularis.

Echinococcus granulosus (Eg) and Echinococcus multilocularis (Em) are the two most widely prevalent types of echinococcosis. Several diagnostic methods have been developed for detecting Eg and Em. However, some limitations, such as being time-consuming, needing expensive instruments, or exhibiting low sensitivity, make these methods unsuitable for on-site detection. In this study, a dual-RPA assay was established to detect and differentiate Eg and Em. The primer concentration ratio, reaction time, and reaction temperature of the dual-RPA were optimized. The result showed that the primer concentration ratio of Eg:Em was 400 nM:400 nM, and the best amplification efficiency was obtained by reacting at 38 °C for 20 min. The sensitivity, specificity, and repeatability of the assay were also tested. The assay's detection limit for both Eg and Em was 10 copies/µL. The assay showed reasonable specificity by testing ten parasitic nucleic acids. The assay's intra- and inter-batch coefficients of variation were below 10%, which indicates robust reproducibility of the assay. Finally, to validate the performance of the dual-RPA assay, it was compared with real-time PCR by using 86 clinical nucleic acid samples. The coincidence rate of Eg between dual-RPA and TaqMan real-time PCR was 96.51%, and the coincidence rate of Em between dual-RPA and TaqMan real-time PCR was 98.84%, indicating its potential for accurate clinical diagnosis. Therefore, this study established a rapid and sensitive dual-RPA assay that can rapidly detect and differentiate Eg and Em in one reaction tube and provided a new assay for the detection of echinococcosis in the field.

A multiplex RPA-CRISPR/Cas12a-based POCT technique and its application in human papillomavirus (HPV) typing assay.

Persistent infection with high-risk human papillomavirus (HR-HPV) is the primary and initiating factor for cervical cancer. With over 200 identified HPV types, including 14 high-risk types that integrate into the host cervical epithelial cell DNA, early determination of HPV infection type is crucial for effective risk stratification and management. Presently, on-site immediate testing during the HPV screening stage, known as Point of Care Testing (POCT), remains immature, severely limiting the scope and scenarios of HPV screening. This study, guided by the genomic sequence patterns of HPV, established a multiplex recombinase polymerase amplification (RPA) technology based on the concept of "universal primers." This approach achieved the multiple amplification of RPA, coupled with the CRISPR/Cas12a system serving as a medium for signal amplification and conversion. The study successfully constructed a POCT combined detection system, denoted as H-MRC12a (HPV-Multiple RPA-CRISPR/Cas12a), and applied it to high-risk HPV typing detection. The system accomplished the typing detection of six high-risk HPV types (16, 18, 31, 33, 35, and 45) can be completed within 40 min, and the entire process, from sample loading to result interpretation, can be accomplished within 45 min, with a detection depth reaching 1 copy/µL for each high-risk type. Validation of the H-MRC12a detection system's reproducibility and specificity was further conducted through QPCR on 34 clinical samples. Additionally, this study explored and optimized the multiplex RPA amplification system and CRISPR system at the molecular mechanism level. Furthermore, the primer design strategy developed in this study offers the potential to enhance the throughput of H-MRC12a detection while ensuring sensitivity, providing a novel research avenue for high-throughput detection in Point-of-Care molecular pathogen studies.

Albumin promoter-driven FlpO expression induces efficient genetic recombination in mouse liver.

Tissue-specific gene manipulations are widely used in genetically engineered mouse models. A single recombinase system, such as the one using Alb-Cre, has been commonly used for liver-specific genetic manipulations. However, most diseases are complex, involving multiple genetic changes and various cell types. A dual recombinase system is required for conditionally modifying different genes sequentially in the same cell or inducing genetic changes in different cell types within the same organism. A FlpO cDNA was inserted between the last exon and 3'-UTR of the mouse albumin gene in a bacterial artificial chromosome (BAC-Alb-FlpO). The founders were crossed with various reporter mice to examine the efficiency of recombination. Liver cancer tumorigenesis was investigated by crossing the FlpO mice with FSF-KrasG12D mice and p53frt mice (KPF mice). BAC-Alb-FlpO mice exhibited highly efficient recombination capability in both hepatocytes and intrahepatic cholangiocytes. No recombination was observed in the duodenum and pancreatic cells. BAC-Alb-FlpO-mediated liver-specific expression of mutant KrasG12D and conditional deletion of p53 gene caused the development of liver cancer. Remarkably, liver cancer in these KPF mice manifested a distinctive mixed hepatocellular carcinoma and cholangiocarcinoma phenotype. A highly efficient and liver-specific BAC-Alb-FlpO mouse model was developed. In combination with other Cre lines, different genes can be manipulated sequentially in the same cell, or distinct genetic changes can be induced in different cell types of the same organism.NEW & NOTEWORTHY A liver-specific Alb-FlpO mouse line was generated. By coupling it with other existing CreERT or Cre lines, the dual recombinase approach can enable sequential gene modifications within the same cell or across various cell types in an organism for liver research through temporal and spatial gene manipulations.

The development of RT-RPA and CRISPR-Cas12a based assay for sensitive detection of infectious hematopoietic necrosis virus (IHNV).

Infectious hematopoietic necrosis virus (IHNV) is an economically important virus causing significant mortalities among wild and cultured salmonid fish worldwide. Rapid and sensitive diagnostic methods of IHNV are crucial for timely controlling infections. For better detection of IHNV, we have established a detection technology based on the reverse transcription and recombinase polymerase amplification (RT-RPA) and CRISPR/Cas12a to detect the N gene of IHNV in two steps. Following the screening of primer pairs, the reaction temperature and time for RPA were optimized to be 41 °C and 35 min, respectively, and the CRISPR/Cas12a reaction was performed at 37 °C for 15 min. The whole detection procedure including can be accomplished within one hour, with a detection sensitivity of about 9.5 copies/µL. The detection method exhibited high specificity with no cross-reaction to the other Novirhabdoviruses HIRRV and VHSV, allowing naked-eye interpretation of the results through lateral flow or fluorescence under ultraviolet light. Overall, our results demonstrated that the developed RT-RPA-Cas12a-mediated assay is a rapid, specific and sensitive detection method for routine and on-site detection of IHNV, which shows a great application promise for the prevention of IHNV infections.

Comparative analysis of structural dynamics and allosteric mechanisms of RecA/Rad51 family proteins: Integrated atomistic MD simulation and network-based analysis.

Homologous recombination plays a key role in double-strand break repair, stalled replication fork repair, and meiosis. The RecA/Rad51 family recombinases catalyze the DNA strand invasion reaction that occurs during homologous recombination. However, the high sequence differences between homologous groups have hindered the thoroughly studies of this ancient protein family. The dynamic mechanisms of the family, particularly at the residual level, remain poorly understood. In this work, five representative RecA/Rad51 recombinase family members from all major kingdoms of living organisms: prokaryotes, eukaryotes, archaea, and viruses, were selected to explore the molecular mechanisms behind their conserved biological significance. A variety of techniques, including all-atom molecular dynamics simulation, perturbation response scanning, and protein structure network analysis, were used to examine the flexibility and correlation of protein domains, distribution of sensors and effectors and conserved hub residues. Furthermore, the potential communication routes between the ATP-binding region and the DNA-binding region of each recombinase were identified. Our results demonstrate the conserved molecular dynamics of these recombinases in the early stage of homologous recombination, including cooperative motions between regions, conserved sensing and effecting functional residue distribution, and conserved hub residues. Meanwhile, the unique ATP-DNA communication routes of each recombinase was also revealed. These results provide new insights into the mechanism of RecA/Rad51 family proteins, and provide new theoretical guidance for the development of allosteric inhibitors and the application of RecA/Rad51 family proteins.

A rapid and sensitive CRISPR-Cas12a for the detection of Fusobacterium nucleatum.

Fusobacterium nucleatum (Fn), as a conditional pathogen, can cause a range of oral and gastrointestinal diseases. However, existing clinical detection methods require expensive equipment and complex procedures, which are inconvenient for large-scale screening in epidemiological research. The purpose of this study was to establish a reliable, rapid, and inexpensive detection method based on CRISPR/Cas12a technology for the detection of Fn. Specific recombinase polymerase amplification (RPA) primer sequences and crRNA sequences were designed based on the nusG gene of Fn. Subsequently, a fluorescence assay and a lateral flow immunoassay were established using the RPA and CRISPR-Cas12a system (RPA-CRISPR-Cas12a). Sensitivity validation revealed a limit of detection of 5 copies/µL. This method could distinguish Fn from other pathogens with excellent specificity. Furthermore, the RPA-CRISPR-Cas12a assay was highly consistent with the classical quantitative real-time PCR method when testing periodontal pocket samples. This makes it a promising method for the detection of Fn and has the potential to play an increasingly important role in infectious disease testing.IMPORTANCEFusobacterium nucleatum (Fn) naturally exists in the microbial communities of the oral and gastrointestinal tracts of healthy individuals and can cause inflammatory diseases in the oral and gastrointestinal tracts. Recent studies have shown that Fn is closely associated with the occurrence and development of gastrointestinal cancer. Therefore, the detection of Fn is very important. Unlike the existing clinical detection methods, this study established a fluorescence-based assay and lateral flow immunoassay based on the RPA and CRISPR-Cas12a system (RPA-CRISPR-Cas12a), which is fast, reliable, and inexpensive and can complete the detection within 30-40 minutes. This makes it a promising method for the detection of Fn and has the potential to play an increasingly important role in infectious disease testing.

Development of a Rapid Epstein-Barr Virus Detection System Based on Recombinase Polymerase Amplification and a Lateral Flow Assay.

The quality of cellular products used in biological research can directly impact the ability to obtain accurate results. Epstein-Barr virus (EBV) is a latent virus that spreads extensively worldwide, and cell lines used in experiments may carry EBV and pose an infection risk. The presence of EBV in a single cell line can contaminate other cell lines used in the same laboratory, affecting experimental results. We developed three EBV detection systems: (1) a polymerase chain reaction (PCR)-based detection system, (2) a recombinase polymerase amplification (RPA)-based detection system, and (3) a combined RPA-lateral flow assay (LFA) detection system. The minimum EBV detection limits were 1 × 103 copy numbers for the RPA-based and RPA-LFA systems and 1 × 104 copy numbers for the PCR-based system. Both the PCR and RPA detection systems were applied to 192 cell lines, and the results were consistent with those obtained by the EBV assay methods specified in the pharmaceutical industry standards of the People's Republic of China. A total of 10 EBV-positive cell lines were identified. The combined RPA-LFA system is simple to operate, allowing for rapid result visualization. This system can be implemented in laboratories and cell banks as part of a daily quality control strategy to ensure cell quality and experimental safety and may represent a potential new technique for the rapid detection of EBV in clinical samples.

BLM and BRCA1-BARD1 coordinate complementary mechanisms of joint DNA molecule resolution.

The Bloom syndrome helicase BLM interacts with topoisomerase IIIα (TOP3A), RMI1, and RMI2 to form the BTR complex, which dissolves double Holliday junctions and DNA replication intermediates to promote sister chromatid disjunction before cell division. In its absence, structure-specific nucleases like the SMX complex (comprising SLX1-SLX4, MUS81-EME1, and XPF-ERCC1) can cleave joint DNA molecules instead, but cells deficient in both BTR and SMX are not viable. Here, we identify a negative genetic interaction between BLM loss and deficiency in the BRCA1-BARD1 tumor suppressor complex. We show that this is due to a previously overlooked role for BARD1 in recruiting SLX4 to resolve DNA intermediates left unprocessed by BLM in the preceding interphase. Consequently, cells with defective BLM and BRCA1-BARD1 accumulate catastrophic levels of chromosome breakage and micronucleation, leading to cell death. Thus, we reveal mechanistic insights into SLX4 recruitment to DNA lesions, with potential clinical implications for treating BRCA1-deficient tumors.

A multiplex recombinase polymerase amplification assay combined with CRISPR/Cas12a for the detection of respiratory syncytial virus and respiratory adenovirus.

OBJECTIVE: Respiratory syncytial virus (RSV) and respiratory adenovirus (ADV) are two common pathogens that cause acute respiratory tract infections in children. We aimed to develop a rapid method for detecting both pathogens simultaneously. METHODS: The recombinase polymerase isothermal amplification (RPA) method was combined with the CRISPR/Cas detection system. The assay's specificity and sensitivity were explored by designing RPA primers and CRISPR RNAs (crRNAs) through multi-sequence comparisons, optimizing the reaction conditions, and using a fluorescent reading device. The consistency of the test results of 160 clinical pharyngeal swab samples was studied using quantitative polymerase chain reaction (qPCR) results as a comparative control. RESULTS: RSV and ADV could be detected at levels as low as 104 copies/mL and 103 copies/mL, respectively, within 50 minutes with no cross-reactivity with other similar pathogens. For the clinical samples, compared with the qPCR method, the sensitivities for RSV and ADV were 98.1% and 91.4%, respectively, and the detection specificities were both 100%. The Kappa values were greater than 0.95, suggesting a high degree of consistency. CONCLUSION: This method for detecting RSV and ADV is rapid, sensitive, and specific. It can accurately detect mixed infections in a timely manner, making it suitable for use in areas with scarce healthcare resources.

RLP system: A single-tube two-step approach with dual amplification cascades for rapid identification of EGFR T790M.

BACKGROUND: The detection of cancer gene mutations in biofluids plays a pivotal role in revolutionizing disease diagnosis. The presence of a large background of wild-type sequences poses a challenge to liquid biopsy of tumor mutation genes. Suppressing the detection of wild-type sequences can reduce their interference, however, due to the minimal difference between mutant and wild-type sequences (such as single nucleotide variants differing by only one nucleotide), how to suppress the detection of wild-type sequences to the greatest extent without compromising the sensitivity of mutant sequence detection remains to be explored. SIGNIFICANCE: The RLP system addresses the incompatibility between RPA and RT-PCR reactions through a physical separation strategy. Besides, due to the remarkable flexibility of locked nucleic acid probes, the RLP system emerges as a potent tool for detecting mutations across diverse genes. It excels in sensitivity and speed, tolerates plasma matrix, and is cost-effective. This bodes well for advancing the field of precision medicine. RESULTS: The recombinase-assisted locked nucleic acid (LNA) probe-mediated dual amplification biosensing platform (namely RLP), which combines recombinase polymerase amplification (RPA) and LNA clamp PCR method in one tube, enabling highly sensitive and selective detection of EGFR T790M mutation under the help of well-designed LNA probes. This technique can quantify DNA targets with a limit of detection (LoD) at the single copy level and identify point mutation with mutant allelic fractions as low as 0.007 % in 45 min. Moreover, RLP has the potential for the direct detection of plasma samples without the need for nucleic acid extraction and the cost of a single test is less than 1USD. Furthermore, the RLP system is a cascading dual amplification reaction conducted in a single tube, which eliminates the risk of cross-contamination associated with opening multiple tubes and ensures the reliability of the results.

Rapid detection of human adenovirus subgroup B using recombinase polymerase amplification assay.

Human adenovirus subgroup B (HAdV B) is one of the major pathogens of human respiratory virus infections, which has considerable transmission and morbidity in a variety of populations. Therefore, rapid and specific detection of HAdV B in clinical samples is essential for diagnosis. This study aimed to develop a product for rapid nucleic acid detection of HAdV B using recombinase polymerase amplification assay (RPA) and validate the performance of this method by using clinical samples. Results showed that this method achieved a lower limit of detection (LOD) of 10 copies/µL and had no cross-reactivity with other adenovirus subgroups or respiratory pathogens. In addition to high sensitivity, it can be completed within 30 min at 40 °C. There is no need to perform nucleic acid extraction on clinical samples. Taking qPCR as the gold standard, the RPA assay possessed a high concordance (Cohen's kappa, 0.896; 95% CI 0.808-0.984; P < 0.001), with a sensitivity of 87.80% and a specificity of 100.00%. The RPA assay developed in this study provided a simple and highly specific method, making it an important tool for rapid adenovirus nucleic acid detection and facilitating large-scale population screening in resource-limited settings.

MscI restriction enzyme cooperating recombinase-aided isothermal amplification for the ultrasensitive and rapid detection of low-abundance EGFR mutations on microfluidic chip.

The detection of low-abundance mutation genes of the epidermal growth factor receptor (EGFR) exon 21 (EGFR L858R) plays a crucial role in the diagnosis of non-small cell lung cancer (NSCLC), as it enables early cancer detection and facilitates the development of treatment strategies. A detection platform was developed by combining the MscI restriction enzyme with the recombinase-aided isothermal amplification (RAA) technique (MRE-RAA). During the RAA process, "TGG^CCA" site of the wild-type genes was cleaved by the MscI restriction enzyme, while only the low-abundance mutation genes underwent amplification. Notably, when the RAA product was combined with CRISPR-Cas system, the sensitivity of detecting the EGFR L858R mutation increased by up to 1000-fold for addition of the MscI restriction enzyme. This achievement marked the first instance of attaining an analytical sensitivity of 0.001%. Furthermore, a disk-shaped microfluidic chip was developed to automate pretreatment while concurrently analyzing four blood samples. The microfluidic features of the chip include DNA extraction, MRE-RAA, and CRISPR-based detection. The fluorescence signal is employed for detection in the microfluidic chip, which is visible to the naked eye upon exposure to blue light irradiation. Furthermore, this platform has the capability to facilitate early diagnosis for various types of cancer by enabling high-sensitivity detection of low-abundance mutation genes.

Development of a real-time enzymatic recombinase amplification assay for rapid detection of infectious hypodermal and hematopoietic necrosis virus (IHHNV) in shrimp Penaeus vannamei.

Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is classified as a reportable crustacean disease by the World Organisation for Animal Health (WOAH), which causes poor growth in Penaeus vannamei. According to genome sequence alignment analysis, enzymatic recombinase amplification (ERA) primers and probe were designed based on the ORF1 region of IHHNV, and a real-time ERA assay for IHHNV detection (IHHNV-ERA) was established. The experimental results show that IHHNV-F2/IHHNV-R2 and IHHNV-Probe can effectively amplify the target gene, and the sensitivity is 1.4 × 101 copies/µL within 14.97 ± 0.19 min, while the qPCR using primers 309F/309R could reach the detection limit of 1.4 × 101 copies/µL within 21.76 ± 0.63 min, and the sensitivity results of one-step PCR could be as low as 1.4 copies/µL with expense of time and false positives. The IHHNV-ERA system can effectively amplify the target gene at 42 ℃ within 20 min, and has no cross-reaction with white spot syndrome virus (WSSV), Ecytonucleospora hepatopenaei (EHP), Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease (VpAHPND), and healthy shrimp genomic DNA. Test results of practical samples showed that the detection rate of IHHNV-ERA (18/20) was better than the industrial standard qPCR assay (17/20). Compared with the existing technology, the useful results of this detection assay are: (1) get rid of the dependence on the thermal cycle instrument in the PCR process; (2) the experimental procedure is simple, time-consuming and fast; (3) the detection sensitivity is high. This study provides an ERA based detection assay for IHHNV, which can be used not only for the rapid detection of IHHNV infection, but also for the field screening of pathogens. This assay can also be applied to clinical inspection, customs detection, enterprise quality inspection and other fields, and has obvious practical application value.