Study On Luminescent Functional Nanomaterials And Applications In Bio-imaging

Recently, with the development of cell biology, more and more studies have focused on the intracellular active species, cell signal transduction, apoptosis and so on. Visual analysis technology based on the light emitting materials is widely developed for cell biology analysis. Currently, the probes frequently used for biological imaging are organic fluorescence molecules, which provide an effective tools for the imaging of live cells and analysis of the physiology and pathology process. However, the fluorescent dye molecules have the disadvantages of short fluorescence lifetime, light quenching and un-stability. It is an urgent problem to improve the selectivity and accuracy of biological imaging analysis, and to realize the longtime dynamic measurement. With the development of nanotechnology, quantum dot fluorescent probes have been paid much attention in biomedical research because of its narrow emission peaks and good optical stability. Unfortunately, the potential biological toxicity of mostly QDs limits its further application in the field of biological imaging. Except the fluorescent method, the luminescence detection techniques requiring no light excitation, including chemiluminescent and bioluminescent, are scarcely used in the biological imaging analysis because the chemiluminescent is a multicomponent reaction system.At present, new types of nanomaterials emerged rapidly. In order to solve the above problems, two novel nanomaterials, MoS₂ QDs and PIL@SiO2, are developed to bio-image by emission functional modification based on fluorescence and chemical luminescence respectively. Novel fluorescent probes and chemiluminescent probes with the function of cell imaging analysis are obtained.This dissertation mainly includes the following aspects:1, A facile approach for large-scale preparation of MoS₂ QDs by Na intercalation reaction without using any toxic organic reagents was proposed. The MoS₂ QDs were carefully characterized by various techniques including transmission electron microscopy, atomic force microscopy, dynamic light scattering, spectroscopy, in vitro cytotoxicology, and capillary electrophoresis. The as-prepared MoS₂ QDs were strongly fluorescent, highly photo-stable, low cytotoxic, and readily-reactive to thiols. These inherent properties of MoS₂ QDs made them as excellent fluorescent probes for long-term live cell tracing. The results of live cells imaging indicated that the MoS₂ QDs stained cells maintained highly fluorescent after long-term culture, and could be easily traced from other co-cultured cell lines.2, Since the MoS₂ QDs had the advantages of small size, good biocompatibility and easy modification with the thiols, the MoS₂ QDs was surface modified by two pH indicate fluorescent groups?LA-Flu and LA-RhB?. A pH response ratio fluorescent probe?dl-MoS₂? with a wide range of pH detection was developed. Under acidic condition, the fluorescence intensity of LA-Flu was decreased, and the fluorescence intensity was increased under alkaline condition. On the contrary, under acidic condition, the fluorescence intensity of LA-RhB was increased, and the fluorescence intensity was decreased under alkaline condition. The ratio of two fluorescence intensity could reflect the pH value. Compared with pH fluorescence probe with single wavelength fluorescent response, the ratiometric fluorescent probes effectively eliminated the error caused by the concentration factors of the probes. While most single wavelength pH response fluorescence probe with the scope of the pH response limited in the range of pKa ± 1, dl-MoS₂ responses in the entire intracellular p H range?pH = 4-8? by two different pKa fluorescence ligands. At the same time, the response range of dl-MoS₂ to pH could be regulated by the ligand ratio on the surface of MoS₂ QDs.3, The mitochondrial-targeting pH response ratio fluorescent probe?mito-MoS₂? is prepared by covalently linking a mitochondria-targeting ligand?triphenylphosphonium, TPP? and a pH indicator?RhB? onto MoS₂ QDs. For this nanoprobe, the MoS₂ QDs serve as the carrier and the reference in the ratio fluorescent probe. The nanoprobe displays excellent water dispersibility, satisfactory cell permeability, high sensitivity and selectivity and very low cytotoxicity. Following the living cell uptake, this nanoprobe can specifically target and stain the mitochondria, and it can detect the mitochondrial pH in Hela cells, as well as the endogenously produced acid of mitochondrial upon stimulation by PMA.4, The rational design and fabrication of a poly?ionic liquid? nanoreactor?PIL? can be used for H2O2 chemiluminescent imaging intercellular and in vivo?c-PIL@SiO2?. The nanoreactor is composed of core/shell structure. The unique amphiphilic PIL core composes by charged ionic liquid moieties?hydrophilic domain? and long alkyl chains?hydrophobic domain?. The hydrophobic domain is used to load peroxalate and dye, and can restrain the hydrolysis of peroxalate, while the hydrophilic domain can provide the path for H2O2 entering into the nanoreactor rapidly. The mesoporous silica shell acts as an “exoskeleton” to provide high mechanical/chemical stability and hydrophilic nature to the chemiluminescent probe. The particle size of c-PIL@SiO2 is ca 100 nm. Laser scanning confocal imaging show the c-PIL@SiO2 can enter the RAW264.7 cells in 5 min with no injury. It is shown that the PIL is capable of imaging H2O2 intracellular and in vivo during immune response. The arthritis model of mice is detected by small animal imaging system, the chemiluminescent probes realize the luminescence imaging in vitro and in vivo. It also shows that chemiluminescent probe exhibits no apparent toxicity, thus holding potential for high-contrast diagnostic imaging.