Application Of Manganese-based Doped Carbon Dots In ROS Regulation

Metal-doped carbon dots(M-CDs)have shown great application value in many fields,such as biosensing,biological imaging,catalysis,disease treatment and so on,due to their simple synthesis method,excellent physical and chemical properties and good biocompatibility.However,M-CDs with enzyme activity are mainly concentrated in Mn,Cu,Fe and Co,and there are only a handful of studies on the application of M-CDs with enzyme activity in ROS regulation.Therefore,it is necessary to carry out the research on ROS regulation of M-CDs,so as to provide guidance and support for the application and development of M-CDs.In this paper,by adjusting the precursors,metal sources and synthesis methods of manganese-based doped carbon dots,manganese-doped carbon dots(Mn-CDs)with oxidase properties and manganese-copper bimetallic doped carbon dots(Mn,Cu-CDs)with multienzyme properties were synthesized by hydrothermal method and microwave method,respectively.Through the exploration of their structures and properties,the effect of Mn-CDs on inhibiting cell activity and the application of Mn,Cu-CDs in scavenging ROS in cigarette smoke were studied.The main research contents and conclusions are as follows:(1)Mn-CDs(～5 nm)with typical spherical morphology was obtained by hydrothermal method at 200℃ for 10 hours with ethylenediaminetetraacetic acid disodium salt(EDTA-2Na)as precursor and manganese acetate tetrahydrate as metal source.The characterization results show that Mn doping can enhance the electron transport capacity of CDs and increase the effective sp2 domain of Mn-CDs.Further studies show that the high catalytic ability of MnCDs is attributed to the synergistic effect of Mn doping and pyrrole nitrogen.On the one hand,the introduction of Mn atoms will affect the spin density and charge distribution of CDs,thereby reducing the band gap and accelerating the catalytic reaction of CDs.On the other hand,the formation of pyrrole nitrogen and the increase of its content are beneficial to accelerate the electron flow between carbon atoms and improve its catalytic performance.In addition,when the oxidase activity of Mn-CDs was systematically studied,it was found that its catalytic activity was mainly excited by ultraviolet light and Mn-CDs could stably show excellent oxidase activity in a wide temperature range,NaCl concentration range and metal salt solution.In addition,the catalytic ability of Mn-CDs was verified in vitro.Mn-CDs could be easily taken up by cells and produce ROS under ultraviolet light irradiation,thus successfully inhibiting the activity of HeLa cells and 4T1 cells.(2)Mn,Cu-CDs(～6 nm)with multi-enzyme characteristics was obtained by microwave method at 540 W microwave power for 15 minutes using EDTA-2Na and ethylenediamine(EDA)as precursors,and manganese chloride tetrahydrate and copper chloride dihydrate as metal sources.A series of characterization results have proved the successful synthesis of Mn,Cu-CDs.The experimental results show that Mn,Cu-CDs has superoxide dismutases-like(SOD-like)activity,hydroxyl radical(·OH)scavenging ability and catalase-like(CAT-like)activity.Its good thermal stability and the ability to scavenge superoxide anion(·O2-)and ·OH lay a foundation for its application in cigarette filters.Adding Mn,Cu-CDs solid powder as a ROS scavenger into cigarette filters can effectively eliminate ROS in cigarette smoke,which provides a new strategy for the improvement of cigarette filters.The above research shows that CDs with different enzyme activities can be obtained by regulating the precursors,metal sources and synthesis methods of manganese-based doped carbon sites,which can meet the different needs of ROS regulation.Mn-CDs can induce ROS in cells under ultraviolet irradiation,and it exhibits excellent inhibitory effect on cell activity.Mn,Cu-CDs can effectively remove 60.67%ROS in cigarette smoke,thus reducing the harm of excessive ROS to human health.