Synthesis And Blood Compatibility Evaluation Of Fluorescent Carbon Dots

Fluorescent carbon dots(size < 10 nm) as a new member of carbon nanomaterials, have similar optical properties with traditional semiconductor quantum dots. Compared to traditional semiconductor quantum dots which could release heavy metal elements that may cause potential harm to environment and human health, fluorescent carbon dots are environment-friendly. Besides, fluorescent carbon dots, due to the advantages of a wide range of raw materials, simple preparation process, low cell toxicity and excitation wavelength-dependent photoluminescence, have potential applications in the fields of biological probe, bio-imaging, cell labeling, biosensor, disease diagnosis and drug delivery, etc. In these biomedical applications, fluorescent carbon dots would unavoidably contact blood tissue in vivo. The unknown interactions would affect not only the in vivo fate of the fluorescent carbon dots themselves but also the normal functions of the blood tissue and the whole organism. At present, there is rarely a report on the complex interactions. Therefore, the blood compatibility evaluations of fluorescent carbon dots are essential, which will help to guide the safe application of fluorescent carbon dots and to provide lots of information for further design and utility of fluorescent carbon dots. The specific contents of this paper are listed as follow: 1. Preparation of α-cyclodextrin-based fluorescent carbon dots and their cell imaging applicationIn this part, fluorescent carbon dots with blue fluorescence were prepared firstly by hydrothermal carbonization of α-cyclodextrin at 200°C for 18 hours. The physicochemical characteristics of the fluorescent carbon dots were analyzed by using high resolution transmission electronmicroscopy(HRTEM), Zeta potential analyzer, UV-visible spectrophotometer, fluorescence spectrophotometer, fluorescence microscope, Fourier transformed infrared spectrophotometer(FTIR). The potential application for cell imaging of the fluorescent carbon dots was further explored by using confocal laser scanning microscope and flow cytometer. 2. Blood compatibility evaluation of the α-cyclodextrin-based fluorescent carbon dotsIn this part, the blood compatibility of α-cyclodextrin-based fluorescent carbon dots was systematically studied in vivo and in vitro:(1) in vitro effect of the fluorescent carbon dots on morphology and lysis of human red blood cells, structure and conformation of plasma protein fibrinogen, blood coagulation, complement activation, and platelet activation;(2) in vivo effect of different doses of the fluorescent carbon dots on important organs and blood coagulation. The results showed that the safety of the fluorescent carbon dots has strong concentration dependence. 3. Hyperbranched polyglycerol conjugated fluorescent carbon dots with improved biocompatibility for bio-imaging and drug deliveryIn this part, we presented a simple and effective technique of anionic ring opening polymerization(ROP) to functionalize the fluorescent carbon dots with hyperbranched polyglycerol(HPG) and successively prepared CDs-g-HPG with green fluorescence. The product was composed with the fluorescent carbon dots as a core and the HPG as a shell. The advantages of this unique structure are as follows:(1) HPG can be utilized to enhance biocompatibility of the fluorescent carbon dots;(2) the HPG shell can efficiently prevent the aggregation of the fluorescent carbon dots in the biological applications;(3) HPG possesses three-dimensional structure and abundant functional groups(-OH) that can be used to further modify of the fluorescent carbon dots;(4) the thickness of HPG shell is controllable;(5) the hydrophobic core of the fluorescent carbon dots can provide a possibility of loading hydrophobic drugs. Besides, we also studied the effect of different concentrations of the fluorescent carbon dots and CDs-g-HPG on cytotoxicity, red blood cells morphology and lysis in vitro.