Rational Design Of Multifunctional Fluorescent Nanodots And Their Biomedical Applications

Fluorescent nanodots(such as carbon dots and organosilica nanodots)have played an important role in many fields of biomedical research.However,the applications of many fluorescent nanodots in the biomedical field have been limited because of their excitation wavelength-dependent fluorescence emission,short excitation and emission wavelengths,and low fluorescence quantum yield.In this thesis,by employing the appropriate reaction precursors and optimizing their molar ratios and the reaction conditions,we prepared fluorescent nanodots with excitation wavelength-independent emission,long-wavelength excitation and emission,and high quantum yields,and tested their capacity for biological detection and cell recognition.In detail,we have carried out the following three studies:(1)The synthesis of sulfur-doped organosilica nanodots(S-OSi NDs),and their application in the detection of metal ions and glutathione(GSH).Firstly,we prepared the S-OSi NDs via a one-pot solvothermal treatment of urea,citric acid,and bis[3-(triethoxysilyl)propyl]tetrasulfide in N,N-dimethylformamide,which could be used to detect metal ions(Fe³⁺,Cu²⁺,[Pd Cl₄]^2–,Ag⁺,Hg²⁺,and Bi³⁺)and realize the imaging of intracellular metal ions.Furthermore,the nanoparticals formed by mixing S-OSi NDs and metal ions(Cu²⁺,Ag⁺,Hg²⁺,and Bi³⁺)could detect GSH,from which we could achieve the identification of cancer/normal cells due to the overexpression of GSH in cancer cells.(2)The application of S-OSi NDs in the differentiation of dead/live animal,bacterial,and fungal cells.The S-OSi NDs were used to achieve the staining of different dead/live animal,bacterial,and fungal cells,and the shortest staining time and minimum staining concentration of these cells were investigated.Compared to the commercial dye Red dots which can selectively stain dead cells,the S-OSi NDs had better staining properties,which were expected to be a novel nanoprobe to distinguish dead/live cells.(3)The preparation of ultrabright green-emissive carbon dots and their application in the identification of dead/live cells.The monosaccharides(glucose,galactose,and fructose)and disaccharides(sucrose,lactose,and maltose)were used to separately react with rose bengal via a one-pot hydrothermal method to prepare green-emissive carbon dots with excitation wavelength-independent fluorescence emission and ultrahigh fluorescence quantum yield(?100%).It was found that the carbon dots were not endocytosed by live animal,bacterial,or fungal cells,but could effectively stain the dead animal,bacterial,and fungal cells,which was useful for the differentiation of dead/live cells.