As a new type of environmental pollutant, microplastics (MPs) can adsorb residual organochlorine pesticides (OCPs) in the soil and pose a severe threat to the soil ecosystems. To understand the interaction between soil MPs and OCPs, the sorption of two kinds of OCPs, including hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs), on polyethylene (PE) microplastics in soil suspension was studied through sorption kinetics and isotherm models. The effects of solution/soil ratio and MPs diameter on sorption were examined. The kinetic experiment results show that the sorption equilibrium was 12 h， and the sorption process of OCPs on MPs can be well described by a pseudo-second-order model. The Freundlich model (R² = 0.942-0.997) provides a better fit to the sorption isotherm data than the Langmuir model (R² = 0.062-0.634), indicating that the sorption process takes place on the nonuniform surface of MPs. The MPs had a good sorption effect on OCPs when the solution/soil ratio was from 75:1 to 100:1. As the diameter of MPs increases, the sorption capacity decreases. These results provide support for further research on microplastic pollution in soil.

Infectious diseases are extremely important public health issues, where the design of effective, rapid, and convenient detection platforms is critical. In this study, we coupled SuCas12a2, a novel Cas12 family RNA-targeting nuclease, with conventional PCR and recombinase polymerase amplification (RPA), respectively, to develop novel detection approaches, named PCR-SuCas12a2 and RPA-SuCas12a2. SuCas12a2 possesses collateral cleavage activity and cuts the additional single-stranded RNA (ssRNA) added to the reaction system once the ternary complex RNA-SuCas12a2-CRISPR RNA (crRNA) is formed. SuCas12a2 is specifically activated, where the cleaved fluorescent-labeled probes release fluorescent signals, with the strength of the fluorescent signal being proportional to the concentration of nucleic acids specifically bound to crRNA. Simultaneous transcription and SuCas12a2 detection can be performed in a single tube by introducing the T7 promoter sequence into the forward primer. Entamoeba histolytica (E. histolytica) and Mycoplasma pneumoniae (M. pneumoniae) were used as proof specimens to evaluate the performance of the platform. PCR-SuCas12a2 has excellent capabilities, including high specificity with no cross-reactivity from other species and ultra-sensitivity that achieves a detection of one copy per reaction for E. histolytica and M. pneumoniae. However, the sensitivity of the RPA-SuCas12a2 assay was 10² copies per reaction, which was inferior to PCR-SuCas12a2. Clinical samples were obtained from suspected infection patients of E. histolytica and M. pneumoniae, and used to evaluate the systems demonstrated 100 % specificity. The technique shows robust performance and suggests great potential for point-of-care testing of other pathogens to facilitate effective management and control of the spread of diseases.

A micromixer is one of the most significant components in a microfluidic system. A three-dimensional micromixer was developed with advantages of high efficiency, simple fabrication, easy integration, and ease of mass production. The designed principle is based on the concepts of splitting–recombination and chaotic advection. A numerical model of this micromixer was established to characterize the mixing performance for different parameters. A critical Reynolds number (Re) was obtained from the simulation results. When the Re number is smaller than the critical value, the fluid mixing is mainly dependent on the mechanism of splitting–recombination, therefore, the length of the channel capable of complete mixing (complete mixing length) increases as the Re number increases. When the Re number is larger than the critical value, the fluid mixing is dominated by chaotic advection, and the complete mixing length decreases as the Re number increases. For normal fluids, a complete mixing length of 500 µm can be achieved at a very small Re number of 0.007 and increases to 2400 µm as the Re number increases to the critical value of 4.7. As the Re number keep increasing and passes the critical Re number, the complete mixing length continues to descend to 650 µm at the Re number of 66.7. For hard-to-mix fluids (generally referring to fluids with high viscosity and low diffusion coefficient, which are difficult to mix), even though no evidence of strong chaotic advection is presented in the simulation, the micromixer can still achieve a complete mixing length of 2550 µm. The mixing performance of the micromixer was also verified by experiments. The experimental results showed a consistent trend with the numerical simulation results, which both climb upward when the Re number is around 0.007 (flow rate of 0.03 μm/min) to around 10 (flow rate of 50 μm/min), then descend when the Re number is around 13.3 (flow rate of 60 µm/min).

Infectious diseases are extremely important public health issues, where the design of effective, rapid, and convenient detection platforms is critical. In this study, we used conventional PCR coupled with SuCas12a2, a novel Cas12 family RNA-targeting nuclease, to develop a detection approach. SuCas12a2 possesses collateral cleavage activity and cuts the additional single-stranded RNA (ssRNA) added to the reaction system once the ternary complex RNA-SuCas12a2-CRISPR RNA (crRNA) is formed. SuCas12a2 is specifically activated, where the cleaved fluorescent-labeled probes release fluorescent signals, with the strength of the fluorescent signal being proportional to the concentration of nucleic acids specifically bound to crRNA. Simultaneous transcription and SuCas12a2 detection can be performed in a single tube by introducing the T7 promoter sequence into the forward primer. Entamoeba histolytica was used to evaluate the performance of the platform. PCR-SuCas12a2 has excellent capabilities, including high specificity with no cross-reactivity from other species and ultra-sensitivity that achieves a detection of one copy per reaction. There were five samples from amoebiasis patients confirmed by indirect immunofluorescence assay that were used as proof specimens, where the PCR-SuCas12a2 assay demonstrated 100% specificity. Furthermore, we replaced conventional PCR with recombinase polymerase amplification (RPA) to simplify the procedure for producing amplicons harboring the T7 promoter sequence. The sensitivity of the RPA-SuCas12a2 assay was 10 ² copies per reaction, which was inferior to PCR-SuCas12a2, and demonstrated 100% specificity. The technique shows robust performance and suggests great potential for point-of-care testing of other pathogens to facilitate effective management and control of the spread of diseases. Abstract Figure: Figure abstract