Preparation And Characterization Of Fluorescent Carbon Nanoparticles And Their Application In The Cell Labeling

With the continuous achievements and progresses in nanotechnology, nano-material has been demonstrating wide and wonderful application prospects in modern life. Nano-materials have been regarded to be the most promising material in the 21st century, due to their novel structures, unique physical and chemical properties, and those nano-effects. As a new nanomaterial, carbon nanoparticles (CNPs), owing to their peculiar properties, have attracted great interest and attention to scientists. Compared to nanodiamond, graphene, carbon nanotubes and traditional quantum dots, threre have been some difficulties in the preparation methods and separation techniques for fluorescent CNPs. And thus, a shortage of associated publications on this topic has been loomed largely.In the biomedical field, staining and modified labeling are important technologies in the identification for cells and molecules. The traditional organic dyes have been used as practical labeling reagents. However, these traditional organic reagents are unable to overcome the shortcomings of its own, such as easy to photolysis, and the products are often toxic and harmful; usally a short fluorescent lifetime; poor in biocompatibility; difficult to carry out multi-color marking at the same time. New fluorescent reagents (such as markers of metal nanoparticles, quantum dots, nano-composite particles) are qualified to get rid of those drawbacks possessed by traditional organic labeling reagents and thus have been used broadly in biomedical field.As a new kind of quantum dots, compared with the conventional organic fluorescent dyes, CNPs retain remarkable advantages over those old labeling reagents, say, low toxicity, water-solublity, high fluorescent intensity with satisfied stability, no fluorescence quenching during multiple excitation; wide excitation spectral width; narrow in emission peaks, symmetric and no overlapping peaks; good biocompatibility. So CNPs is hopeful to be a new fluorescent labeling reagent in future, just as quantum dots did. There are following contents in this thesis:1. New fluorescent carbon nanoparticles (CNPs) were prepared from the soot of candle under a condition of smoldering combustion. The soot was refluxed in an aqueous solution of mixed oxide acids, i.e.30% H2O2/ACOH (V:V= 2:1). The CNPs solid were extracted several times with ether. The structure and properties of CNPs were characterized with fluorescence spectroscopy (FS), infrared spectroscopy (IR), elemental analysis (EA) and scanning electron microscopy (SEM). The CNPs have the strongest emission peak at 445 nm and the best excitation wavelength sited at 325 nm. The shape of fluorescence emission peak is symmetrical, and fluorescent CNPs have maximum fluorescence intensity in the vicinity of pH 7.0 solution. The IR analysis showed that on the surface of fluorescent CNPs, some oxidized functional groups, such as-OH,-COOH or other oxidized groups have been introduced during the refluxing in the solution of mixed oxidative acids. The hydrophilicity of the CNPs increased significantly and at the same time, the fluorescent activity was produced strikingly after the CNPs are dealt with the oxidative reaction.2. MTT assay was used to select the cell inoculation density, and simultaneously to measure the toxicity of CNPs in Hela cells and HepG-2 cells in vitro. The results showed that fluorescent CNPs are able to enter into the Hela cells and promote the proliferation of Hela cells, but did not induce apoptosis and injury to the cells. But for the HepG-2 cells, CNPs showed inhibition of cell proliferation.3. The fluorescent CNPs were applied as the tool of fluorescent markers to label the Hela cells and HepG-2 cells. The react situation was observed with a special instrument, laser scanning confocal fluorescence microscopy (LSCFM). A bright field of vision of fluorescence was observed in Hela cells after they had been labelled with CNPs. The results demonstrated that CNPs had exerted a quite strong fluorescent activity. However, in the case of HepG-2 cells, CNPs failed to do the job of lebeling successfully.Owing to their outstanding novel merits, such as non-toxic, chemical inertness and exellent biocompatibility, we believe that, before a long time, CNPs will become a gorgeous star in cell labeling and sure enough, they will initiate a brilliant feat in biomedical field.