Synthesis,Characterization Of Supra Carbon Nanodots And Diagnosis,photothermal Therapy For Tumor Cells

Carbon dot materials are easy to prepare,have a wide range of raw materials,high quantum yield,and low toxicity.They are widely used in fluorescence detection,cell imaging,and tumor treatment.Supra-carbon nanodots are formed by self-assembly of carbon nanodots,which can utilize near-infrared light and have high photothermal conversion efficiency.Supra carbon nanodots have good biocompatibility and high utilization rate of near-infrared light.They have great application in biomedicine and other fields.In this article,we have designed and synthesized carbon nanodots which respond to the pH of cancer cells for detection and treatment of cancer cells.The difference in the acidity of cancer cell and normal cell environment is used to form different supra carbon nanodots.Differences in fluorescence intensity and photothermal conversion efficiency enable cancer cell diagnosis and selective photothermal treatment.The main research contents are as follows:1.We use citric acid and dicyandiamide as raw materials to synthesize blue fluorescent carbon nanodots(B-CNDs)with pH response aggregation,and adjust the pH of the solution with HCl for B-CNDs protonation.Supra carbon dots(S-CNDs)have high light-to-heat conversion performance in the infrared region.Compared with B-CNDs,the size of S-CNDs increased significantly,the formed visible-NIR absorption peaks at 450-900 nm.The solution color changed from yellow to black.When changing the acidity of the solution to optimize the formation conditions of S-CNDs,it was found that the accumulation of B-CNDs suddenly increased under the pH environment of the cancer cells(pH=4.7),and the formed S-CNDs had weaker fluorescence and larger size.Aggregation couples different B-CNDs orbits,the energy level changes,and the UV-visible absorption peaks increase and redshift.When light irradiates S-CNDs,photo-generated electrons relax mainly in a non-radiative way.Therefore,S-CNDs can effectively convert light into heat,and the light-to-heat conversion efficiency is up to 42.13 % under 650 nm irradition.S-CNDs have excellent biocompatibility,good water solubility,and can efficiently utilize near-infrared light.It's the first time to realize the aggregation of B-CNDs to form near-infrared S-CNDs by adjusting the environmental pH,which provides more possibilities for the synthesis of near-infrared carbon nanodots.2.The chapter successfully used the B-CNDs synthesized above for selectively imaging and photothermal treatment of cancer cells.The degree of B-CNDs aggregation increases with acidity,the pH of cytoplasm in cancer cells is lower than that in normal cells,and the degree of B-CNDs aggregation in cancer cells is greater and fluorescence quenching is more severe.The fluorescence of cancer cells is significantly weaker than normal cells.The experimental results show that B-CNDs effectively distinguish cancer cells from normal cells.When B-CNDs protonated aggregate in cancer cells,S-CNDs with large size and high photothermal conversion efficiency are generated.Cancer cells and normal cells were irradiated with 650 nm light,and the death rate of cancer cells was as high as 90 %,while normal cells still survived.Therefore,B-CNDs can be used for selectively imaging for cancer cells and photothermal therapy.This is also the first time to use the self-characteristics of carbon nanodots to achieve selective photothermal treatment of cancer cells.