Carbon Dot@MXene Nanozymes with Triple Enzyme-Mimic Activities for Mild NIR-II Photothermal-Amplified Nanocatalytic Therapy.

Nanozymes have shown promising potential in disease treatment owing to the advantages of low-cost, facile fabrication, and high stability. However, the highly complex tumor microenvironment (TME) and inherent low catalytic activity severely restrict the clinical applications of nanozymes. Herein, a novel mild hyperthermia-enhanced nanocatalytic therapy platform based on Z-scheme heterojunction nanozymes by depositing N-doped carbon dots (CDs) onto Nb2 C nanosheets is constructed. CD@Nb2 C nanozymes not only display outstanding photothermal effects in the safe and efficient NIR-II window but also possess triple enzyme-mimic activities to obtain amplified ROS levels. The triple enzyme-mimic activities and NIR-II photothermal properties of CD nanozymes are enhanced by the construction of Z-scheme heterojunctions owing to the accelerated carrier transfer process. More importantly, the introduction of mild hyperthermia can further improve the peroxidase-mimic and catalase-mimic activities as well as the glGSH depletion abilities of CD@Nb2 C nanozymes, thereby producing more ROS to efficiently inhibit tumor growth. The combined therapy effect of CD@Nb2 C nanozymes through mild NIR-II photothermal-enhanced nanocatalytic therapy can achieve complete tumor eradication. This work highlights the efficient tumor therapy potential of heterojunction nanozymes.

Bitter and astringent substances in green tea: composition, human perception mechanisms, evaluation methods and factors influencing their formation.

Green tea is popularly known for its pleasant flavor and health-care functions. Bitterness and astringency are the two important quality attributes of green tea that enrich tea flavor. Although many research works have focused on the flavor formation of green tea, the review articles about bitterness and astringency is limited. This review article summarizes the major components of bitter and astringent substances in green tea, their sensory perception mechanism, factors influencing the formation of these substances, and the evaluation methods of bitterness and astringency. This review will shed light on the subsequent studies in tea flavor, and provide deeper insight for the research of bitterness and astringency in other foods.

Separation and mechanism elucidation for six structure-like matrine-type alkaloids by micellar liquid chromatography.

A mixed micellar liquid chromatography (MLC) method, the mobile phase consisting of anionic surfactant SDS and nonionic surfactant Brij35, was firstly developed for the separation and determination of six structure-like matrine-type alkaloids, including matrine, oxymatrine, sophocarpine, oxysophocarpine, sophoridine, and oxysophoridine. The factors influencing the resolution of the six alkaloids were systematically investigated and optimized, including the micellar composition and concentration, column temperature, the type and amount of organic solvent, and the pH values in the mobile phases. Under the optimized separation conditions, the six matrine-type alkaloids could be easily isocratically eluted with a baseline separation within 22 min. Under the designated conditions (SDS concentration from 10 to 50 mM, Brij35 from 5 to 30 mM, pH 3 and 5% 1-propanol), the hydrophobic selectivity was negatively correlated with the concentration of Brij35 but not with SDS. The functional group selectivity of the carbonyl group, double bond, and diastereomers, all decreased with the increase in percentage of SDS in the mixed micellar phase, because the strong electrostatic force masks other molecular forces which can discriminate the retention of the analytes. Therefore, such a combination in surfactants of MLC is a powerful strategy to increase the selectivity by adjusting the balance among the various molecular interaction forces influencing analytes' retention. Finally, the developed method was successfully used to separate and determine the contents of main alkaloids in Sophora medicinal plants, S. flavescens Ait. In summary, the mixed MLC is a valuable approach to separate and determine the structure-like multi-component natural samples.