Preparation Of Red Fluorescent Carbon Quantum Dots And Its Application In Cell Imaging And Photodynamic Therapy

As a new kind of fluorescent carbon nanomaterials,carbon quantum dots are superior to current semiconductor quantum dots and organic fluorescent materials in photostability,water solubility,biocompatibility and toxicity,and have shown great application value in bioimaging,ion detection,cancer treatment and drug delivery.Although great progress has been made in the research of carbon quantum dots in recent years,there are still some shortcomings.At present,most of the carbon quantum dots emit blue or green light with shorter wavelength,which limits their applications in biology and medicine to a certain extent.In order to solve this problem,researchers urgently need to find a suitable method to prepare carbon quantum dots which can emit long-wavelength fluorescence,especially red-emitting carbon quantum dots.In this paper,the preparation of long-wavelength carbon quantum dots and their biological applications are studied.The main research contents and results are as follows:1.Carbon quantum dots with different fluorescence properties were prepared from different precursors.Among them,nitrogen-doped yellow-emitting carbon quantum dots(Y-CDs)were prepared from o-phenylenediamine by one-step hydrothermal method,and nitrogen-phosphorus co-doped red-emitting carbon quantum dots(R-CDs)were prepared by adding phosphoric acid.The results show that both carbon quantum dots have good water solubility and stability,and they all exhibit emission that did not depend on the change of excitation wavelength.By comparing the optical properties and surface states of Y-CDs and R-CDs,we believe that the differences of luminescence properties of the two kinds of carbon quantum dots are mainly related to the surface states.2.The cytotoxicity of R-CDs and Y-CDs was evaluated by MTT assay and Calcine-AM/PI co-staining method,respectively.The experimental results show that the two carbon quantum dots have no obvious cytotoxicity,but show high cytotoxicity when irradiated with specific light.Subsequently,R-CDs and Y-CDs were applied in cell imaging respectively,which showed good imaging results.Then the ability of R-CDs and Y-CDs to produce singlet oxygen was investigated by using SOSG as probe.The results show that both carbon quantum dots can produce singlet oxygen under specific laser irradiation.3.The nude mice inoculated with A549 tumor pieces were selected for in vivo photodynamic therapy experiments.After irradiation with 532 nm laser,the growth of tumors in nude mice injected with R-CDs was significantly inhibited,and the weight of nude mice has a sight change.At the same time,the liver,lung,spleen,kidney and heart of nude mice in the treatment group were pathologically analyzed by H&E staining.The results showed that there was no obvious damage to the organs and indicators in the blood analysis fall normal range.These results suggest that R-CDs can be used as potential photosensitizers in photodynamic therapy of tumors.