Enzyme-like Activity Of Carbon Dot And Its Application In Targeting To Nitrogen Signaling Molecules For Inhibiting Neuronal Death

Traumatic brain injury（TBI）is the leading cause of death and disability worldwide,and the morbidity is increasing,causing huge social problems and economic burdens to the world.China has made certain developments in basic research and clinical treatment of TBI,and is gradually narrowing the gap with international advanced levels and continuously deepening the field of brain injury research.TBI mainly causes primary damage and secondary damage,and secondary damage can mainly lead to changes in blood brain barrier（BBB）permeability and the production of large amounts of free radicals.The generation of a large amount of free radicals will aggravate the degree of damage and seriously threaten human health.Therefore,it is of great significance for human health to study the free radical scavengers in the recovery and treatment of TBI using the reaction mechanism and damage mechanism of free radicals.In this paper,by synthesizing carbon quantum dots and studying the physical and chemical properties of carbon quantum dots,we will explore the ability of quantum to scavenge free radicals and treat TBI.The experimental content and results are as follows:1.Carbon dot（CD）was synthesized by microwave heating the solution of L-lysine and L-cysteine at 90℃.The physical-chemical characteristic of CD,such as size,groups,valence states and bonding,were studied by dynamic light scattering（DLS）,atomic force microscope（AFM）,transmission electron microscope（TEM）,Fourier infrared spectrometer（FTIR）,X-ray photoelectron spectroscopy（XPS）,and fluorescence spectroscopy（PL）.The above results show that CD is an ultra-small（1.83nm）carbon dot with a graphene structure in the center and functional group on the surface.2.Through the study of the enzyme-like activity of CD quantum dots,the enzyme-like activities of superoxide dismutase（SOD）,catalase（CAT）and glutathione peroxidase（GPx）of CD were tested.From the perspective of enzyme activity,the internal causes of CD in the treatment of TBI were analyzed.In order to characterize the scavenging ability of carbon quantum dots to free radicals,including nitrogen free radicals and oxygen free radicals,UV spectrophotometer,microplate reader,and electronic spin resonance（ESR）were used to quantitatively characterize the scavenging capacity.The research results show that CD not only has anti-oxidation ability,but also can efficiently remove nitrogen free radicals,such as DPPH,ONOO^-,^·NO,but only partially remove oxygen free radicals such as^·OH and O₂^·-,indicating that CD has the ability to efficiently target the removal of nitrogen-related free radicals.3.In vitro experiments,H₂O₂ and LPS were used to stimulate cells to induce free radicals.Cells were stained and fluorescently analyzed to study the scavenging ability of CD at the cellular level.The experimental results show that the ability of CD to scavenge nitrogen free radicals is much higher than than that of oxygen free radicals.4.Establishing a traumatic brain injury model and treating mice by injecting carbon quantum dot,we analyzed various physiological indicators（lipid peroxide,H₂O₂concentration,superoxide dismutase（SOD）activity and GSH/GSSG）,cell shape and number around the injury area,and distance,time and time of staying in platform,indicating that CD has a significant therapeutic effect on traumatic brain injury.