Visual Detection of ACE I/D Polymorphism Using T-ARMS-PCR Combined with a Lateral Flow Assay and Its Clinical Application

RART-LAMP: One-Step Extraction-Free Method for Genotyping within 40 min

Loop-mediated isothermal amplification (LAMP) is a commonly used alternative to PCR for point-of-care detection of nucleic acids due to its rapidity, sensitivity, specificity, and simpler instrumentation. While dual-labeled TaqMan probes are widely used in PCR for single-nucleotide polymorphism (SNP) genotyping, real-time LAMP primarily relies on turbidimetry or intercalator fluorescence measurements, which can be non-specific and generate false-positive results. In this study, we propose a closed-tube, dual-labeled RNA-modified probes and RNase H II-assisted real-time LAMP (RART-LAMP) method for SNP genotyping. Our findings indicate that (1) fluorescence signals were predominantly derived from probe hydrolysis rather than hybridization, (2) temperature-controlled hybridization between the probe and template ensured the specificity of SNP analysis, and (3) RNase H II hydrolysis between the target containing SNP sites and probes did not exhibit sequence specificity. Our RART-LAMP approach demonstrated excellent performance in genotyping C677T clinical samples, including gDNA extracted from blood, saliva, and swabs. More importantly, saliva and swab samples could be directly analyzed without any pretreatment, indicating promising prospects for nucleic acid analysis at the point of care in resource-limited settings.

Rapid and Sensitive Detection of Fungicide-Resistant Crop Fungal Pathogens Using an Isothermal Amplification Refractory Mutation System

Fungicide abuse leads to the emergence of fungicide-resistant fungal pathogens, thus posing a threat to agriculture and food safety. Here, we developed an isothermal amplification refractory mutation system (termed iARMS) allowing us to resolve genetic mutations, enabling rapid, sensitive, and potentially field-applicable detection of fungicide-resistant crop fungal pathogens. iARMS yielded a limit of detection of 25 aM via a cascade signal amplification strategy of recombinase polymerase amplification (RPA) and Cas12a-mediated collateral cleavage at 37 °C within 40 min. Specificity for fungicide-resistant Puccinia striiformis (P. striiformis) detection was guaranteed by RPA primers and the flexible sequence of gRNA. The iARMS assay allowed us to detect as low as 0.1% cyp51-mutated P. striiformis that showed resistance to the demethylase inhibitor (DMI), which was 50 times more sensitive than the sequencing techniques. Thus, it is promising for the discovery of rare fungicide-resistant isolates. We applied iARMS to investigate the emergence of fungicide-resistant P. striiformis in western China and found that its proportion was over 50% in Qinghai, Sichuan, and Xinjiang Province. iARMS can serve as a molecular diagnostic tool for crop diseases and facilitate precision plant disease management.

A label-free strategy for visual genotyping based on phosphate induced coloration reaction

Genetic variation plays a crucial role in disease occurrence and development. However, current genotyping strategies not only require a long turnaround time for DNA purification, but also depend on sophisticated apparatus and complex data interpretation, which seriously limits their application in point of care diagnostic test scenarios. In this study, by integrating phosphate induced coloration reaction and loop-mediated isothermal amplification, a rapid and portable strategy for straightforward genotyping has been established to cater to the demand of precision medicine. By employing phosphate ions produced during the amplification as a signal generator, not only can the genotyping result be interpreted with only naked eye from a low-cost label-free strip, but also the amplification efficiency is increased to facilitate genotyping with a robust biological specimen ignoring DNA polymerase inhibitors. Moreover, the introduction of alkaline lysis for DNA release allows whole blood to be identified accurately avoiding DNA purification. As a proof of concept, the insertion/deletion polymorphisms of the angiotensin-converting enzyme, a crucial factor associated with cardiovascular and cerebrovascular diseases, has been selected as a model to evaluate the performance of this method. Accurate results can be obtained from as low as 1 ng genomic DNA within 30 min. For clinical specimen detection, a concordance rate up to 100% has been found compared with PCR-based electrophoresis. Thus, this novel strategy may serve as a promising tool for straightforward genotyping to provide timely diagnostic information, especially in resource-poor medical institutions.

Phosphate induced coloration reaction facilitates visual genotyping and the target variant can be accurately identified within 30 min from blood directly.