Synthesis Of Fluorescence Carbon Dots And Applications In Photodynamic And Photothermal Therapy

Carbon Dots(CDs),as a new type of carbon nanomaterials,have excellent performance in fluorescence imaging,sensing and drug delivery,because of their advantages of stability,biocompatibility,permeability,and low cost.In recent years,researchers have developed carbon dots as an efficient agent for photodynamic therapy(PDT)and photothermal therapy of cancer with less side-effect.In the second chapter,a novel methylene blue(MB)-based fluorescent carbon dot(MBCD)was synthesized by hydrothermal method using methylene blue as carbon source,which was applied in photodynamic therapy of tumors.MB-CDs exhibited the advantages of uniform size and distribution,good stability,low cytotoxicity,low cost and easy preparation.In this work,nitrogen and sulfur elements were introduced to increase its absorption wavelength and singlet oxygen yield respectively in this MB-CDs as an excellent photosensitizer.In vitro cell experiments showed that MB-CDs could be irradiated by low light intensity(30 mW),and the killing rate of cancer cells was more than 70%.In addition,mice experiments showed that MBCDs were used as photosensitizers to kill tumors and inhibit their growth.In Chapter 3,a novel fluorescent carbon dot(CY7-CDs)was synthesized by hydrothermal method using heptamethylcyanine dye(CY7)as carbon source.The absorption and emission wavelength of CY7 located in near infrared region,therefore CY7 could be used as not only photosensitive materials but fluorescent imaging agent.However,the stability of CY7 was not good,which was prone to self-aggregation with obvious cytotoxicity.Compared with the CY7,the CY7-CDs retained photodynamic properties,while reduced the cytotoxicity and increased water solubility and stability.In addition,the maximum emission peaks of CY7-CDs were at 580 nm and 846 nm respectively,which could be used for dual-mode fluorescence imaging.The CY7-CDs also exhibited a photothermal effect besides fluorescence imaging,which was applied to tumor treatment by photodynamic-photothermal combination therapy.