A simple methodology for RNA isolation from bacteria by integration of formamide extraction and chitosan-modified silica purification

Establishment of rapid extraction and sensitive detection system of trace corn syrup DNA in honey

Honey adulteration with exogenous syrup has become a common phenomenon, and current detection techniques that require large instruments are cumbersome and time-consuming. In this study, a simple and efficient method was developed by integrating the rapid extraction of nucleic acids (REMD) and recombinase polymerase amplification (RPA), known as REMD-RPA, for the rapid screening of syrup adulteration in honey. First, a rapid extraction method was developed to rapidly extract corn syrup DNA in five minutes to meet the requirements of PCR and RPA assays. Then, the RPA method for detecting endogenous maize genes (ZssIIb) was established, which could detect 12 copies/μL of the endogenous maize gene within 30 min without cross-reacting with other plant-derived genes. This indicated that the RPA technique exhibited high sensitivity and specificity. Finally, the REMD-RPA detection platform was used to detect different concentrations of corn syrup adulteration, and 1 % adulteration could be detected within 30 min. The 22 commercially available samples were tested to validate the efficacy of this method, and the established RPA was able to detect seven adulterated samples in less than 30 min. Overall, the developed method is rapid, sensitive, and specific, providing technical support for the rapid field detection of honey adulteration and can serve as a reference for developing other field test methods.

Amino-modified silica membrane capable of DNA extraction and enrichment for facilitated isothermal amplification detection of Mycoplasma pneumoniae

Herein, we developed a facile integrated Mycoplasma pneumoniae diagnosis platform by combining amino-modified silica membrane (AMSM)-based nucleic acids fast extraction and enrichment with colorimetric isothermal amplification detection. AMSM demonstrates a strong ability to capture and enrich nucleic acids in complicated biological matrices, and the purified AMSM/nucleic acids composite could be directly used to perform isothermal amplification including denaturation bubble-mediated strand exchange amplification (SEA) and loop-mediated isothermal amplification (LAMP) reactions. Through comparing clinical specimens, excellent performance of AMSM-based SEA assay with 93.33% sensitivity and 100% specificity relative to real-time PCR was observed, and for AMSM-based LAMP was 96.67% and 100%, respectively. The diagnostic procedure could be completed within 55 min, and the colorimetric-based visual result further alleviates the use of sophisticated equipment. The proposed approach possesses great potential as a simple and time-saving alternative for point-of-care testing (POCT) of M. pneumoniae in resource-limited regions.

Single-walled carbon nanotubes-based RNA protection and extraction improves RT-qPCR sensitivity for SARS-CoV-2 detection

The false-negative result of nucleic acid testing is an important cause of continued spread of COVID-19, while SARS-CoV-2 RNA degradation during transportation and nucleic acid extraction can lead to false-negative results. Here, we investigated that single-walled carbon nanotubes (SCNTs) could protect RNA from degradation for at least 4 days at room temperature. By constructing magnetism-functionalized SCNTs (MSCNTs), we developed a method that enabled protection and simple extraction of SARS-CoV-2 RNA, and the RNA-bound MSCNTs can be directly used for reverse transcription polymerase chain reaction (RT-qPCR) detection. The experimental results showed that 1 μg of MSCNTs adsorbed up to 24 ng of RNA. Notably, the MSCNTs-based method for extracting SARS-CoV-2 RNA from simulated nasopharyngeal swabs and saliva samples with mean recovery rates of 103% and 106% improved the sensitivity of RT-qPCR detection by 8-32 fold in comparison to current common methods. This improvement was largely attributable to the protection of RNA, enabling increased RNA load for downstream assays.