Rotenone encapsulated in pH-responsive alginate-based microspheres reduces toxicity to zebrafish.

Rotenone is a botanical pesticide and has long been used for control of insect pests and also as a natural piscicide for management of fish populations in many countries. Field application for pest control, however, often encounters the movement of rotenone into surface water due to spray drift or surface runoff after rainfall, which could potentially result in water pollution and unexpected death of fishes. To minimize its effect on freshwater and the problem of fish dying, one solution was to encapsulate rotenone in specific microspheres, limiting its release and reducing its toxicity since rotenone can be quickly degraded under sunlight. In this study, pH-responsive alginate-based microspheres were synthesized to encapsulating rotenone, which were designated as rotenone beads. The rotenone beads, along with alginate beads (devoid of rotenone) were characterized and evaluated for their responses to pH and effects on zebrafish. Results showed that the microspheres had high loading efficiency (4.41%, w/w) for rotenone, and rotenone beads well responded to solution pH levels. The cumulative release rates of rotenone from the beads were 27.91%, 42.72%, and 90.24% at pH 5.5, 7.0, and 9.0, respectively. Under acidic conditions, the rotenone release rate was lower due to hydrogen bonding. On the contrary, rotenone became more quickly released at the high pH due to intermolecular repulsion. The toxicity of rotenone beads to zebrafish and fish embryos at a pH of 5.5 was reduced by 2- and 4-fold than chemical rotenone. Since pH levels in most freshwater lakes, ponds, and streams vary from 6 to 8, rotenone release from the beads in such freshwater could be limited. Thus, the synthesized rotenone beads could be relatively safely used for pest control with limited effects on freshwater fishers.

[Value of serum procalcitonin combined with soluble triggering receptor expressed on myeloid cells-1 in the differential diagnosis of bacterial and viral diarrhea in children].

OBJECTIVE: To study the value of serum procalcitonin (PCT) combined with soluble triggering receptor expressed on myeloid cells-1 (STREM-1) in the differential diagnosis of bacterial diarrhea and viral diarrhea in children. METHODS: A retrospective analysis was performed on the medical data of 73 children with bacterial infectious diarrhea (bacteria group) and 68 children with viral infectious diarrhea (virus group) who were treated from February 2018 to May 2019. The receiver operating characteristic (ROC) curve was used to analyze the diagnostic efficacy of serum PCT and STREM-1 for bacterial infectious diarrhea and viral infectious diarrhea. RESULTS: Compared with the virus group, the bacteria group had significantly higher detection rates of fecal red blood cells (79% vs 43%, P<0.05) and pus (51% vs 19%, P<0.05), as well as significantly higher serum levels of PCT and STREM-1 (P<0.05). The ROC curve analysis showed that in the differential diagnosis of bacterial infectious diarrhea and viral infectious diarrhea, serum PCT had a cut-off value of 0.97 ng/mL and an area under the ROC curve (AUC) of 0.792, and STREM-1 had a cut-off value of 15.66 ng/mL and an AUC of 0.889. Serum PCT combined with STREM-1 had an AUC of 0.955, which was significantly higher than that of each index alone (P<0.05). CONCLUSIONS: Children with bacterial diarrhea have increased serum levels of PCT and STREM-1 than those with viral diarrhea. Both serum PCT and STREM-1 can be used as the indices for the differential diagnosis of bacterial diarrhea and viral diarrhea in children, and the combined measurement of PCT and STREM-1 can improve the efficiency of differential diagnosis.

Fumigant toxicity and behavioral inhibition of garlic against red imported fire ants (Solenopsis invicta).

In order to control the Solenopsis invicta (S. invicta) in a safe and ecofriendly manner, this study evaluated the fumigating activity of garlic and its effect on the behavior of S. invicta. The volatile compounds and chemical constituents from garlic were collected by solid phase micro-extraction and identified by gas chromatography-mass spectrometry (GC-MS). The results showed that garlic contains 21 compounds, and that diallyl disulfide (46.51%) and (E)-1-Allyl-2-(prop-1-en-1-yl) disulfane (34.68%) were the main constituents in garlic. In addition, garlic showed strong fumigant activity and behavioral inhibition against workers. The LC50 values of diallyl disulfide and methyl allyl disulfide against S. invicta at 12 h were 0.05 and 0.07 µg/L, respectively. The grasping and walking abilities of ants were significantly suppressed. Moreover, minor workers were more susceptible than major workers. Thus, S. invicta can be controlled with garlic and some of its compounds as an eco-friendly approach. Results from the study could provide valuable advances for future fumigant development and possible utility in fumigant use.

pH-responsive λ-cyhalothrin nanopesticides for effective pest control and reduced toxicity to Harmonia axyridis.

In this study, pH-responsive LC@O-CMCS/PU nanoparticles were prepared by encapsulating λ-cyhalothrin (LC) with O-carboxymethyl chitosan (O-CMCS) to form LC/O-CMCS and then covering it with polyurethane (PU). Characterization and performance test results demonstrate that LC@O-CMCS/PU had good alkaline release properties and pesticide loading performance. Compared to commercial formulations containing large amounts of emulsifiers (e.g., emulsifiable concentrate, EC), LC@O-CMCS/PU showed better leaf-surface adhesion. On the dried pesticide-applied surfaces, the acute contact toxicity of LC@O-CMCS/PU to Harmonia axyridis (H. axyridis) was nearly 20 times lower than that of LC EC. Due to the slow-releasing property of LC@O-CMCS/PU, only 16.38 % of LC was released at 48 h in dew and effectively reduced the toxicity of dew. On the pesticide-applied leaves with dew, exposure to the LC (EC) caused 86.66 % mortality of H. axyridis larvae significantly higher than the LC@O-CMCS/PU, which was only 16.66 % lethality. Additionally, quantitative analysis demonstrated 11.33 mg/kg of λ-cyhalothrin in the dew on LC@O-CMCS/PU lower than LC (EC) with 4.54 mg/kg. In summary, LC@O-CMCS/PU effectively improves the safety of λ-cyhalothrin to H. axyridis and has great potential to be used in pest control combining natural enemies and chemical pesticides.

Chitosan-based nanopesticides enhanced anti-fungal activity against strawberry anthracnose as "sugar-coated bombs".

A chitosan-based nanoparticle was prepared using chitosan (CS) and O-carboxymethyl chitosan (O-CMCS). Our study revealed that chitosan/O-carboxymethyl chitosan/tebuconazole nanoparticles (CS/O-CMCS/TBA NPs) exhibited superior antifungal activity, foliar adhesion, and microbial target adhesion performance compared to commercial suspension concentrate (SC). The antifungal activity of CS/O-CMCS/TBA NPs against C. gloeosporioides, with a 3.13-fold increase in efficacy over TBA (SC). We also found that low concentrations of CS/O-CMCS NPs promoted the growth of C. gloeosporioides and enhanced the fungal catabolism of chitosan. Overall, the CS/O-CMCS/TBA NPs were found to possess the remarkable capability to selectively aggregate around pathogenic microorganisms and CS/O-CMCS NPs can enhance the fungal catabolism of chitosan. CS/O-CMCS/TBA NPs, as a "sugar-coated bomb", was a promising asset for effective plant disease management and pesticide utilization through the affinity of chitosan-based nanoparticles and C. gloeosporioides, enabling targeted delivery and targeted release of their encapsulated active ingredient, which was important for the development and application of biocompatible chitosan-based nanopesticides.

Efficiency of mesoporous silica/carboxymethyl ß-glucan as a fungicide nano-delivery system for improving chlorothalonil bioactivity and reduce biotoxicity.

Understanding the lethal effects of pesticides nano formulations on the targeted organisms (pathogens) and the non-targeted organisms (fish, earthworms, etc) is essential in assessing the probable impact of new technologies on agriculture and environment. Here we evaluated the bioactivity and the biotoxicity of new type of fungicide smart-delivery formulation based on conjugating carboxymethylated-ß-glucans on the mesoporous silica nanoparticles (MSNs) surface after loading chlorothalonil (CHT) fungicide in the MSNs pores. The obtained formulation has been characterized with FE-SEM, and HR-TEM. The CHT loading efficiency has been measured with TGA. The bioactivity of the obtained formulation (CHT@MSNs-ß-glucans) has been tested against four pathogens, fusarium head blight (Fusarium graminearum), sheath rot (Sarocladium oryzae), rice sheath blight (Rhizoctonia solani), and soyabean anthracnose (Colletotrichum truncatum) compared with CHT WP 75% commercial formulation (CHT-WP) and technical CHT. The environmental biotoxicity of CHT@MSNs-ß-glucans compared with CHT-WP has been tested toward earthworm (Eisenia fetida) and zebra fish (Danio rerio). The results showed that CHT@MSNs-ß-glucans has an excellent bioactivity against the subjected pathogens with better inhabiting effects than CHT-WP. CHT@MSNs-ß-glucans toxicity to Eisenia fetida was found 2.25 times lower than CHT-WP toxicity. The LC50 of CHT@MSNs-ß-glucans to zebra fish after the first 24h was 2.93 times higher than CHT-WP. After 96h of treatment, the LC50 of CHT@MSNs-ß-glucans was 2.66 times higher than CHT-WP. This work highlighted the necessity to increase the mandatory bioassays of nano formulations with the major non-target organisms in the environmental risk assessment of new pesticide formulations.

Fabrication of sulfoxaflor-loaded natural polysaccharide floating hydrogel microspheres against Nilaparvata lugens (Stal) in rice fields.

BACKGROUND: Nilaparvata lugens (Stal) nymphs and adults aggregate and feed on leaf sheaths at the base of rice plants. It is difficult to apply traditional spray treatments directly onto the plant stems due to the blocking agent produced by leaves. Further, spiders and mirids, the natural enemies of N. lugens (Stal), are directly exposed to the chemicals during spraying. Sulfoxaflor-loaded natural polysaccharide microspheres with good performance were developed and tested in rice fields. The absorption, distribution, and dissipation of sulfoxaflor in rice plants, soil, and water were examined. RESULTS: Sulfoxaflor-loaded natural polysaccharide microspheres were prepared through physical embedding and ionic crosslinking, using citronellol as an oil phase to provide floatation. The sustained release of sulfoxaflor was achieved through swelling and dissolution, indicating that these structures could effectively control pesticide release. Field experiments showed that these microspheres were able to float in water and gather around the stem of rice plants and that their insecticidal effect was remarkably improved compared to that achieved using the suspension concentrate. Results also showed that the residual content of stems following treatment with sulfoxaflor-loaded natural polysaccharide microspheres reached 0.331 mg kg-1 , but was reduced in other parts of the plant. CONCLUSION: In the present study, sulfoxaflor-loaded natural polysaccharide microspheres with optimized properties were successfully prepared. These microspheres produced a better control effect on N. lugens (Stal) compared to the use of the sulfoxaflor suspension concentrate. Their application may help promote the scientific control of target pests in rice fields. © 2020 Society of Chemical Industry.