ABSTRACT
To explore the occurrence characteristics and influencing factors of microplastics in soil in the Danjiangkou Reservoir area, this study collected soil samples from orchards, dryland, paddy fields, and wetland and identified microplastics in soil via density sorting, microscope observation, and Raman spectrometry. The results showed that microplastics were detected in 64 samples collected in the study area, and the abundance ranged from 645 to 15161 n·kg-1. The spatial distribution of microplastics in the bottom of the reservoir was higher than those in the middle and head of the reservoir, and the abundance of microplastics in the surface soil(0-20 cm) was significantly lower than that in the bottom soil(20-40 cm). The main types of microplastics were polypropylene(26.4%) and polyamide(20.2%), the particle size was mainly concentrated between 50-500 µm(75%), and the common shape was fragments(66.2%). Correlation analysis showed that soil microplastic abundance was closely related to land use, distance from water and housing, population density, and soil properties. From the perspective of microplastic pollution risk, 72.1% of the region's microplastic polymer risk index was at level â ¢ and level â £, and there was a certain risk of microplastic pollution in the Danjiangkou Reservoir area. The results of this study can provide support for risk assessment of microplastics.
ABSTRACT
Combined chemo-photothermal therapy of gold nanorods (GNRs) for cancer treatment shows better therapeutic efficiency than mono-chemotherapy, which has gained worldwide interests of scientists and clinician in both laboratory and clinic application. However, high cytotoxicity, declined delivery efficiency, and unsatisfactory therapy effect of the GNRs are still challenging in anti-cancer treatment. Herein, a series of pH-sensitively zwitterionic polypeptide conjugated GNRs were synthesized via a gold-thiol interaction for combination of chemo-photothermal therapy in cervical cancer treatment. The acid-labile hydrazone bond was utilized to incorporate the doxorubicin (DOX) for pH-sensitive drug release under tumoral environment. The as prepared GNRs conjugates demonstrated pH-triggered surface charge conversion from negative to positive when transporting from blood circulation to tumor extracellular environment, which can facilitate the cellular uptake via electrostatic interaction. After cellular internalization, the drug release was promoted by cleavage of the hydrazone in GNRs conjugates under cancer intracellular acid environment. As the effective near-infrared (NIR) photothermal materials, the as prepared GNRs conjugates can absorb NIR photo energy and convert it into heat under irradiation, which can efficiently kill the tumor cells. In cell assay, the GNRs conjugates displayed excellent biocompatibility against normal cell, enhanced cancer cell uptake, and remarkable cancer cell killing effects. In HeLa tumor-bearing mice, the GNRs conjugates demonstrated enhanced tumor inhibition efficacy by combination of chemo-photothermal therapy.
