Preparation and Antibacterial Activity of Thermo-Responsive Nanohydrogels from Qiai Essential Oil and Pluronic F108.

Essential oils (EOs) have been used in cosmetics and food due to their antimicrobial and antiviral effects. However, the applications of EOs are compromised because of their poor aqueous solubility and high volatility. Qiai (Artemisia argyi Levl. et Van. var. argyi cv. Qiai) is a traditional Chinese herb and possesses strong antibacterial activity. Herein, we report an innovative formulation of EO as nanohydrogels, which were prepared through co-assembly of Qiai EO (QEO) and Pluronic F108 (PEG-b-PPG-b-PEG, or PF108) in aqueous solution. QEO was efficiently loaded in the PF108 micelles and formed nanohydrogels by heating the QEO/PF108 mixture solution to 37 °C, by the innate thermo-responsive property of PF108. The encapsulation efficiency and loading capacity of QEO reached 80.2% and 6.8%, respectively. QEO nanohydrogels were more stable than the free QEO with respect to volatilization. Sustained QEO release was achieved at body temperature using the QEO nanohydrogels, with the cumulative release rate reaching 95% in 35 h. In vitro antibacterial test indicated that the QEO nanohydrogels showed stronger antimicrobial activity against S. aureus and E. coli than the free QEO due to the enhanced stability and sustained-release characteristics. It has been attested that thermo-responsive QEO nanohydrogels have good potential as antibacterial cosmetics.

A novel thermal pretreatment method called air frying improves the enzymatic saccharification effect of straw.

Thermal pretreatment is a shared method to improve the efficiency of straw biochemical conversion. However, the process is often accompanied by problems such as the loss of carbon source. The objective of this study was to develop a novel thermal pretreatment method, called air frying, with less loss of biodegradable organic matter and favorable surface hydrophilicity. After pretreatment of two straws, the sugar yields were improved, and the improvement effect of corn stover was more significant. The total saccharification rate of corn stover increased from 31.31 ± 1.06% to 44.77 ± 1.23%, and the cellulose conversion rate increased from 44.10 ± 1.85% to 67.44 ± 2.37%. Functional groups with lower polarity on the surface were oxidized into the one with stronger polarity, so the hydrophilicity was enhanced. The surface roughness decreased, the surface tended to be flat, the original pores collapsed, and the average pore size increased, which was more conducive to the binding of enzyme and active site. The matching relationship between the optimal conditions and substrate, and the possibility of scaling up need further study.