Labeling Fusarium oxysporum with silicon carbide quantum dots and long-term-distance fluorescent imaging for living cells

Fluorescence microscopy has allowed the functional study of various molecules that have been identified in living cells. The capabilities of this technique have generated a huge interest in developing new probes for labeling molecules and observing changes in their cellular activities. Quantum dots (QDs) based on II-VI (e.g., CdSe, CdTe, CdS, and ZnSe) and III-V (e.g., InP and InAs) semiconductors have attracted considerable scientific interest over the past two decades for their remarkable luminescent properties. However, the widely used CdX semiconductor QDs were found to be cytotoxic through the release of free metallic ions (cadmium ions for instance). Therefore, it becomes clear that the cytotoxicity strongly influencing biological cell functioning is one of the major limiting factors for the application of II-VI QDs in efficient living cell imaging. Recently, silicon carbide(SiC) QDs has been growing attention for people with the advantages of non-toxic, good biocompatible due to its simple preparation process and excellent optical properties. Especially, for the Fusarium oxysporum, inspection of its infection mechanism needs to be fluorescent marked and long-term-distance tracing with vivo cells. The paper focus on two aspects for SiC QDs: fabrication and the vivo cells marking and long-term-distance fluorescent imaging. Firstly, the aqueous SiC QDs was prepared by SiC particles, which was prepared via self-propagating combustion in the mixture chemical etchant of nitric and hydrofluoric acid. Latticed-hollow of silicon carbide particles will be easily obtained because of SiC particles fabrication characteristics like nonequilibrium thermal forming leading to many defaults on the surface. Processed by broken and dispersed with ultrasonic cavitation, high-speed centrifugation, non-cytotoxic labeling materials of silicon carbide QDs were obtained. The microstructure and optical properties of QDs were measured and analyzed. The silicon carbide QDs are nearly spherical feature and its diameter is shorter than its' Bohr diameter (5.4 nm), which result in excellent optical properties. There is inherent relationship between the emission color-displaying and the sizes of the SiC QDs. Multi-color fluorescence can be displayed in one exciting wavelength according to different size. Emission light will show blue shift following the decrease diameter. In this study, the emission wavelength of QDs with 5 and 2 nm diameter is 470 and 439 nm, respectively. The Fusarium oxysporum labeling and long-term-distance fluorescent imaging for living cells were processed. Firstly, conidiums were marked on the cell membrance with SiC QDs which next enter into the cell via endocytosis and stably labeling. Further results indicated that SiC QDs can show long-term-distance vivo fluorescent image because of its non-cytotoxicity. Moreover, the results of Fourier transform infrared spectroscopy (FTIR) indicated that some hydrophilic organic functional groups, such as COO-, O-, OH- and so on, on the surface of QDs were established in the process of etching which plays an important role in stable marking for living cells. The problems of interaction between the Fusarium oxysporum and plant root, procedure and mechanism of infecting, new prevention method for Fusarium wilt can be hopefully solved. Furthermore, the SiC QDs is a potential marking materials compared to the traditional fluorescent organic dye. The methods of multi-targets marking and long-term-distance tracing can give the materials and technical support for the biological theory researching fields, such as living cells and its substructure, molecular events, cells behaviors and so on.