A functional nucleic acid-based fluorescence sensing platform based on DNA supersandwich nanowires and cation exchange reaction.

Accurate and sensitive analysis of p53 DNA is important for early diagnosis of cancer. In this work, a fluorescence sensing system based on DNA supersandwich nanowires and cation exchange (CX)-triggered multiplex signal amplification was constructed for the detection of p53 DNA. In the presence of p53 DNA, the DNA self-assembles to form a DNA supersandwich nanowire that generates long double-stranded DNA. Subsequently, the cation exchange (CX) reaction between ZnS and Ag+ was utilized to release free Zn2+. With the participation of Zn2+, DNAzyme catalyzes the hydrolysis of numerous catalytic molecular beacons, resulting in a greatly enhanced fluorescence signal due to the cycling of DNAzyme. The fluorescence values increased in proportion to the concentrations of p53 DNA in the range of 10 pM to 200 nM, and a detection limit (LOD) of 2.34 pM (S/N = 3) was obtained. This method provides an effective strategy for the quantitative detection of p53 DNA.

[Characteristics and Planting Safety Assessment of As Content in Dryland Soil and Maize in Guizhou Province].

In order to understand the distribution characteristics of As content in dryland soils and maize seeds in Guizhou province and to evaluate the safety of maize cultivation, 468 natural soil samples, 1260 dryland surface soil samples, and 980 corresponding maize seed samples were systematically collected to determine their As content and basic physicochemical properties. The degree of contamination of the samples was evaluated by using the single-factor contamination index method. The results showed that: ① the range of ω(As) in dryland soil was 0.35-758.53 mg·kg-1, with a geometric mean of 23.28 mg·kg-1. The independent sample T-test showed that the As content of dryland soil in Guizhou province was significantly higher than that of natural soil ω(As) 21.29 mg·kg-1 (P<0.01), indicating the existence of arsenic accumulation effects in dryland soil; compared with the screening value of the "Agricultural Land Soil Pollution Risk Management and Control Standard" (GB 15618-2018), the excess rate of soil samples was 33.81%. ② Corn seed ω(As) ranged from 0.001 to 0.868 mg·kg-1, with a mean value of 0.064 mg·kg-1, and 0.61% of the corn seed samples exceeded the limit value of "Limits of Contaminants in Foods" (GB 2762-2017), with the exceeding points distributed in Bijie City, Qianxinan Prefecture, and Tongren City. ③ When corn seeds were used as feed and grain, maize could be safely grown in dryland soils in Guizhou province. This study showed that the soil As pollution in the dryland of Guizhou province was relatively serious, and overall safe maize cultivation can be achieved; however, the cultivation of maize around the As-related non-ferrous metal mining areas is still of concern.

Ratiometrically homogeneous electrochemical biosensor based on the signal amplified strategy of dual DNA nanomachines for microRNA analysis.

Precise and sensitive microRNA (miRNA) analysis is very significant for early disease diagnosis. In this work, a dual DNA nanomachines-based homogeneous electrochemical biosensor was constructed for the sensitively ratiometric detection of miRNA by a nicking enzyme (Nt.AlwI)-assisted cycling signal amplification strategy. The Co-based metal organic frameworks (Co-MOFs) and toluidine blue (TB) were employed as signal probes and internal reference probes, respectively. The introduction of internal reference probes can actually calibrate the interferent factors of the analytical system to improve the stability in detection procedure. In addition, with the help of the magnetic separation technique, the homogeneous electrochemical biosensor provides a more simpler way for the development of immobilization-free electrochemical miRNA biosensors, avoiding the complex modification procedure of traditional electrochemical biosensing interfaces. Consequently, taking advantages of this proposed dual DNA nanomachines-based homogeneous electrochemical biosensor, the highly sensitive and selective detection of miRNA-141 as model could be accomplished in ranging from 1 fM to 10 nM with detection limit of 0.46 fM. This strategy exhited good sensitivity and stability to integrate the nicking enzyme-powered dual DNA nanomachines with the ratiometric electrochemical output modes, which open new opportunities for the sensitive and reliable diagnosis of miRNA-related diseases.

[Accumulation Effects and Health Risks of Heavy Metals in Rice in Location-based Cadmium Anomaly Area in Liuzhou].

In order to explore the migration and transformation characteristics of soil heavy metals in rice in an area of ground source cadmium anomaly and to evaluate the safe planting of rice, a total of 91 pairs of soil and rice samples were collected from paddy fields in the typical area of Liuzhou city, Guangxi province, and the contents of heavy metals such as Cd, soil pH, and organic matter were tested. The results showed that:① Cd, Cu, Ni, and Zn in the paddy field exceeded the background values of 92.31%, 34.07%, 36.26%, and 90.11%, respectively. Compared with the screening values in the Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard, Cd and Zn exceeded 30.53% and 25.26%, respectively. Super standard points were mainly distributed in Fushi Town. ② Cd and Ni exceeded 35.16% and 3.30%, respectively, and Daliang town had the highest Cd enrichment coefficient and Cd exceeded rate. ③ Correlation analysis showed that soil pH was the main influencing factor of heavy metals in rice, and Cd and Ni had similar pollution sources in rice. ④ The results of rice health risk assessment showed that the THQ value of rice Cd in Daliang town was greater than 1.0, indicating the potential health risk of rice Cd in this area. The TTHQ values were all greater than 1.0, indicating that the risks to children were higher than those to adult women, which were higher than those of adult men, showing that reasonable dietary structure is crucial to prevent heavy metal intake in different ages and genders. Therefore, there are certain risks in rice planting in the Liuzhou area of ground source cadmium anomaly, which need to be controlled using different safety utilization measures.