Dynamic aqueous multiphase reaction system for simple, sensitive and quantitative one-pot CRISPR-Cas12a based molecular diagnosis

Recently, CRISPR-Cas technology has opened a new era of nucleic acid-based molecular diagnostics. However, current CRISPR-Cas-based nucleic acid biosensing has largely a lack of the quantitative detection ability and typically requires separate manual operations. Herein, we reported a dynamic aqueous multiphase reaction (DAMR) system for simple, sensitive and quantitative one-pot CRISPR-Cas12a based molecular diagnosis by taking advantage of density difference of sucrose concentration. In the DAMR system, recombinase polymerase amplification (RPA) and CRISPR-Cas12a derived fluorescent detection occurred in spatially separated but connected aqueous phases. Our DAMR system was utilized to quantitatively detect human papillomavirus (HPV) 16 and 18 DNAs with sensitivities of 10 and 100 copies within less than one hour. Multiplex detection of HPV16/18 in clinical human swab samples were successfully achieved in the DAMR system using 3D-printed microfluidic device. Furthermore, we demonstrated that target DNA in real human plasma samples can be directly amplified and detected in the DAMR system without complicated sample pre-treatment. As demonstrated, the DAMR system has shown great potential for development of next-generation point-of-care molecular diagnostics.

Effects of SO₂ on optical properties of secondary organic aerosol generated from photooxidation of toluene under different relative humidity

Secondary organic aerosol (SOA) have great impacts on air quality, climate change and human health. The composition and physicochemical properties of SOA differ a lot for they originated under different atmospheric conditions and from various precursors and oxidations. In this work, photooxidation experiments of toluene were performed under four conditions (dry, dry with SO2, wet, and wet with SO2) to investigate the effect of SO2 under different relative humidity on the composition and optical properties of SOA at the wavelength of 375 nm and 532 nm. According to our results, the increase of humidity enhances not only light absorption, but also scattering property of SOA. Highly conjugated oligomers formed through multiphase reaction might be the reasons of this phenomenon. Adding SO2 slightly lower the real part of complex refractive index (n) of SOA: ndry, SO2