Hydrothermally Derived Green Carbon Dots from Broccoli Water Extracts: Decreased Toxicity, Enhanced Free-Radical Scavenging, and Anti-Inflammatory Performance.

Biomass carbon dots (CDs) derived from natural plants possess the advantages of low cost, photostability, and excellent biocompatibility, with potential applications in chemical sensing, bioimaging, and nanomedicine. However, the development of biomass CDs with excellent antioxidant activity and good biocompatibility is still a challenge. Herein, we propose a hypothesis for enhancing the antioxidant capacity of biomass CDs based on precursor optimization, extraction solvent, and other conditions with broccoli as the biomass. Compared to broccoli water extracts, broccoli powders, and broccoli organic solvent extracts, CDs derived from broccoli water extracts (BWE-CDs) have outstanding antioxidant properties due to the abundant C═C, carbonyl, and amino groups on their surface. After optimization of the preparation condition, the obtained BWE-CDs exhibit excellent free-radical scavenging activity with an EC50 of 68.2 µg/mL for DPPH• and 22.4 µg/mL for ABTS•+. Cytotoxicity and zebrafish embryotoxicity results indicated that BWE-CDs have lower cytotoxicity and better biocompatibility than that of CDs derived from organic solvents. In addition, BWE-CDs effectively scavenged reactive oxygen species (ROS) in A549 cells, 293T cells, and zebrafish, as well as eliminating inflammation in LPS-stimulated zebrafish. Mechanistic studies showed that the anti-inflammatory effect of BWE-CDs was dependent on the direct reaction of CDs with free radicals, the regulation of NO levels, and the upregulation of the expression of SOD and GPX-4. This work indicates that the antioxidant activity of CDs could be enhanced by using solvent extracts of biomass as precursors, and the obtained BWE-CDs exhibit characteristics of greenness, low toxicity, and excellent antioxidant and anti-inflammatory activities, which suggests the potential promising application of BWE-CDs as an antioxidant nanomedicine for inflammatory therapy.

[Spatial dstribution of the net anthropogenic phosphorus input (NAPI) to the Dongting Lake basin, China.] / æ´žåº­æ¹–æµåŸŸäººç±»æ´»åŠ¨å‡€ç£·è¾“å ¥åŠå ¶ç©ºé—´åˆ†å¸ƒ.

Based on the net anthropogenic phosphorus input (NAPI) model, we estimated the NAPI of the Dongting Lake basin and its sub-basins from 1985 to 2015, and analyzed the spatio-temporal distributions and variations. The results showed that there was an increasing trend at first and then a decrease in the Dongting Lake basin. The NAPI values in the area in 1985, 1995, 2005 and 2015 were 7.00, 9.20, 10.33, 10.01 kg·hm-2·a-1, respectively. The largest input source changed from the net food and feed import in 1985 to phosphorus fertilizer during 1995-2015. The mean annual input of phosphorus fertilizer, with an average value of 6.01 kg·hm-2·a-1 accounting for 65.8% of NAPI; followed by the food and feed import, the annual average value was 2.65 kg·hm-2·a-1, accounting for 29.0%, and the least was non-food phosphorus, with an average annual value of 0.47 kg·hm-2·a-1, accounting for 5.2%. Spatially, the distribution of NAPI in the Dongting Lake basin showed the characteristics of high in the northeast region and low in the west, which was mainly consistent with distribution of local agriculture. The average annual NAPI values in sub-basin from high to low ranked as following: Dongting Lake area, Xiangjiang River downstream, Zijiang River upstream, Xiangjiang River upstream, Lishui River area, Yuanjiang River upstream, Yuanjiang River downstream and Zijiang River downstream. The highest NAPI was found in the Dongting Lake area, increasing from 13.01 kg·hm-2·a-1 in 1985 to 24.14 kg·hm-2·a-1 in 2015. Agricultural production and population growth were the main contributors to the current input of net phosphorus, and the negative ecological effects of which could not be ignored.