Design And Preparation Of A New Type Of Magnetic Carbon Quantum Dots And Its Application For CTC Detection

Magnetic fluorescent nanoparticles, with the advantages of magnetic materials and fluorescent materials, can realize a variety of functions such as the magnetic separation, targeted identification, fluorescence imaging and magnetic resonance imaging at the same time. It has a good application prospect and received high attention of scientific researchers in numerous fields, but its biological toxicity and biological compatibility need to be improved. Because the microfluidic chip technology can control the samples accurately in size of micro-nano, the microfluidic chip technology combined with magnetic fluorescent marker method can realize the high sensitivity separation and detection of samples. If microfluidic chip technology combined with fluorescent magnetic nanoparticles was used in the study of circulating tumor cells technology, it can realize the separation, enrichment and detection of circulating tumor cells at the same time, be conducive to realize the accurate detection and analysis of circulating tumor cells, and improve the handling technology of tumour cells.The main research work and results are as follows:①Magnetic carbon quantum dots were designed and prepared. The carbon quantum dots were prepared by microwave-assisted hydrothermal synthesis, its fluorescence yield was up to 58.6%. Magnetic carbon quantum dots were fabricated through the electrostatic adsorption by that carbon quantum dots was assembled to the surface of ferroferric oxide nano particles. The synthesis process was monitored with potentiostat, particles distribution instrument and spectrometer. Infrared spectrum and TEM were used to characterize the structure of magnetic carbon quantum dots. The results showed that the particle size of magnetic carbon quantum dots, with the fluorescence properties of up/down conversion luminescence, was about 200 nm, and optical performance stable. The biggest excitation and emission wavelength of magnetic carbon quantum dots were 345 nm and 432 nm respectively. Magnetic carbon quantum dots can emit three kinds of fluorescence, blue, green and red, under different excitation wavelength, and can realize fluorescent tags for cells.②Based on cells phagocytosis, self-made magnetic carbon quantum dots were used to mark hepatocytes L02 and separate and detect Hep G2 cells from mixed cells. The homemade carbon quantum dots and magnetic carbon quantum dots were found to have low biological toxicity and good biological compatibility by MTT method. Interaction of the two kinds of nanometer materials and liver L02 were investigated, it was found that carbon quantum dots and magnetic carbon quantum dots marked the cytoplasm of L02 cells, and can realize fluorescent tags in only 1 h. When the concentration of magnetic carbon quantum dots was 60 μg·m L-1 and the layer of carbon quantum dot(n) were great than or equal to 9, cell fluorescence imaging figure got clear. According to principle of magnetic separation, the Hep G2 cells would be separated with 30 s from L02 cells in an external magnetic field, and the separation efficiency was 90.3%. The results show that the magnetic carbon quantum dots can be used for cell markers, separation and detection.③According to the principle of magnetic separation, glass- PDMS microfluidic chip for magnetic separation of circulating tumor cells was designed and producted. Hep G2 cells were marked with magnetic carbon quantum dots probes through immune marking method. Glass- PDMS microfluidic chip was used for magnetic separation and fluorescence detection. The optimal flow velocity was 16 μL·min-1. The concentration of Hep G2 cells and fluorescence value has a linear relationship when the concentration range vary from 2 cells·m L-1 to 25 cells·m L-1. The capture rate of Hep G2 cells from blood sample was 82.0%.④MOFF- DEP cell analysis microfluidic chip, integrated porous flow channel(MOFF) and dielectrophoresis(DEP), was designed for separation and capture of cells. Separation conditions were optimizated. When the velocity is 80 μL·min – 1, the excitation voltage and frequency of the array fork electrode were 5 V and 1 MHZ, reapectively, and the excitation voltage and frequency of parabolic electrode 5 V and 40 KHz, Hep G2 cells can be the separated effectively. Thus, separation and fluorescence detection system of CTC with MOFF/DEP microfluidic chip was established. The separation rate of Hep G2 cells from blood was 95.0% by the method. The micro system greatly reduces the volume of the detection system, and provides an experimental basis to achieve the miniaturization and integration of the detection system.