Reverse Transcription Recombinase Polymerase Amplification Coupled with CRISPR-Cas12a for Facile and Highly Sensitive Colorimetric SARS-CoV-2 Detection.

The outbreak of the pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) calls for an urgent unmet need for developing a facial and cost-effective detection method. The requirement of well-trained personnel and sophisticated instrument of current primary mean (reverse transcription polymerase chain reaction, RT-PCR) may hinder the practical application worldwide. In this regard, a reverse transcription recombinase polymerase amplification (RT-RPA) coupled with CRISPR-Cas12a colorimetric assay is proposed for the SARS-CoV-2 detection. The methodology we have described herein utilizes DNA-modified gold nanoparticles (AuNPs) as a universal colorimetric readout and can specifically target ORF1ab and N regions of the SARS-CoV-2 genome. After the virus genome is amplified through RT-RPA, the resulting abundant dsDNA will bind and activate Cas12a. Under trans-cleavage degradation, the capped DNA substrate will be hydrolyzed gradually from AuNPs, demonstrating a change in the surface plasmon resonance (SPR), which can be facially monitored by UV-vis absorbance spectroscopy and naked eye observation. The high amplification efficiency from RT-RPA and Cas12a trans-cleavage process bring the sensitivity of our method to 1 copy of viral genome sequence per test. Notably, under the dual variations inspecting from the isothermal amplification and Cas12a activation process, the false positive events from other beta coronavirus members can be effectively avoided and thus significantly improve the specificity. Furthermore, the reliability of this colorimetric assay is validated by standard clinical samples from the hospital laboratory department. Through integration of the inherently high sensitivity and specificity from an RPA-coupled Cas12a system with the intrinsic simplicity of AuNP-based colorimetric assay, our method increases the practical testing availability of SARS-CoV-2.

Fluorescence resonance energy transfer-based DNA framework assembled split G-quadruplex nanodevices for microRNA sensing.

A DNA framework assembled split G4 nanodevice was fabricated to realize microRNA imaging in living HeLa cells. After hybridization with the target, the separated G4 segments underwent structural transformations, which could initiate fluorescence resonance energy transfer (FRET) processes. Our design may pave a novel way to facilitate applications of the G4 motif.

Engineering of exosome-triggered enzyme-powered DNA motors for highly sensitive fluorescence detection of tumor-derived exosomes.

Tumor-derived exosomes containing multiple proteins originating from parent cancer cells have emerged as biomarkers for cancer diagnosis. Herein, we propose a three-dimensional DNA motor-based exosome assay platform for the selective and sensitive detection of exosomes. The DNA motor used gold nanoparticle (GNP) tracks, consisting of fluorescein-labeled substrate strands and aptamer-locked motor strands. Recognition of the target protein on exosomes by its aptamer unlocked the motor strand and triggered the DNA motor process. Powered by restriction endonuclease, the motor strands autonomously walked along the GNP track. Each movement step cleaved one substrate strand and restored one fluorescein molecule. For exosome detection, the proposed method displayed a broad dynamic range acrossing 5 orders of magnitude with the detection limit as low as 8.2 particles/µL in PBS. The method also exhibited good selectivity among different tumor-derived exosomes and performed well in complex biological samples. The capability to profile exosomal surface proteins efficiently endowed our DNA motor great potential for developing a simple and cost-effective device for clinical diagnosis.

Life-course origins of social inequalities in adult immune cell markers of inflammation in a developing southern Chinese population: the Guangzhou Biobank Cohort Study.

BACKGROUND: Socioeconomic position (SEP) throughout life is associated with cardiovascular disease, though the mechanisms linking these two are unclear. It is also unclear whether there are critical periods in the life course when exposure to better socioeconomic conditions confers advantages or whether SEP exposures accumulate across the whole life course. Inflammation may be a mechanism linking socioeconomic position (SEP) with cardiovascular disease. In a large sample of older residents of Guangzhou, in southern China, we examined the association of life course SEP with inflammation. METHODS: In baseline data on 9,981 adults (≥ 50 years old) from the Guangzhou Biobank Cohort Study (2006-08), we used multivariable linear regression and model fit to assess the associations of life course SEP at four stages (childhood, early adult, late adult and current) with white blood, granulocyte and lymphocyte cell counts. RESULTS: A model including SEP at all four life stages best explained the association of life course SEP with white blood and granulocyte cell count for men and women, with early adult SEP (education) making the largest contribution. A critical period model best explained the association of life course SEP with lymphocyte count, with sex-specific associations. Early adult SEP was negatively associated with lymphocytes for women. CONCLUSIONS: Low SEP throughout life may negatively impact late adult immune-inflammatory status. However, some aspects of immune-inflammatory status may be sensitive to earlier exposures, with sex-specific associations. The findings were compatible with the hypothesis that in a developing population, upregulation of the gonadotropic axis with economic development may obscure the normally protective effects of social advantage for men.