Based On Block Copolymer Of Nano And Biological Imaging Performance Study Of Preparation Of Fluorescent Probe

In recent years, the synthesis and application of amphiphilic block copolymer supramolecular self-assembled nano-microstructure have attracted extensive attention. These block copolymer micelles are featured with spherical morphology of tens to hundreds of nanometers in particle diameter, various special nano-size effect and stability, and are therefore being widely used in chemical catalysis, optical, biological medicine and many other fields. In this thesis, we focused on following four aspects:1) We employed the spherical micelles of amphiphilic block copolymer (PS-b-PAA) as a template to prepare a new kind of core-shell structured fluorescent nanospheres (DPN@NHs). The hydrophobic dyes were encapsulated into the core of the hybrid nanospheres based on the self-assembly of amphiphilic block copolymers followed by shell cross-linking using3-mercaptopropyltrimethoxy-silane (MPTMS) as a cross-linking agent. The as-synthesized DPN@NHs were very uniform in size (50nm) and spherical morphology, and could be highly monodispersed in water. The fluorescent performances of the as-synthesized water-soluble DPN@NHs were greatly enhanced. The nanospheres exhibited no cytotoxicity and negligible cell apoptosis. By co-cultivating with MCF-7cells, DPN@NHs showed the successful cell uptake in cytoplasm regions in a large quantity.2) An organic-inorganic fluorescent nanohybrids with extraordinarily enhanced fluorescent performance was synthesized based on the self-assembly of amphiphilic block copolymers. The thiol-functional group and a fluorescent dye,4-piperidyl-l,8-naphthalic anhydride, could be introduced into the system by a one step method based on the hydrolysis of APTMS and the binding interaction between APTMS and naphthalic anhydride under the presence of NH3. By adjusting the consumption amount of MPTMS, the diameters of the nanohybrids could be easily tuned from50nm to80nm, while the fluorescent yields could be also enhanced. The as-synthesized fluorescent nanocomposites are water-soluble and well-monodispersed in aqueous solution with a remarkably enhanced quantum yield by25times. The in-vitro experiments demonstrated that the nanocomposites exhibited good biocompatibility, large quantity and quick cell uptake, and accurate cell labeling capability.3)The super-hydrophobic pH-responsive fluorophores (NDI) were encapsulted into the self-assembled micelles of amphiphilic diblock copolymer PS-6-PAA for recognizing and mapping the route of cell phagocytosis. With the subsequent shell cross-linking with3-mercaptopropyltrimethoxy-silane (MPTMS),the as-synthesized NDI@HNPs showed a typical spherical morphology with an average diameter of46nm and excellent monodispersity in aqueous solution. The fluorescent quantum yield of NDI@HNPs in acidic medium (pH=4.4) is55times larger than that in neutral medium, showing a real-time pH-sensitive fluorescent indication feature with fast response and large stokes shift. The encapsulation of NDI leads to a large stokes shift of～60nm in aqueous solution, which enables the nanoprobes to be a high quality imaging contrast agent. Its characteristic fluorescence response to pH is beneficial to the intracellular cancer cell labeling and organelle targeting, and can be employed to reveal the processes of its effective entry into the cancer cells, and the subsequent accumulation into the endolysosome and the further escape. This smart high quality contrast agent offers an easy and direct protocol to response the micro-environmental pH change and traces the phagocytosis pathway of nano-objects.4) To test the versatility of our synthetic process, we prepared a series of NIR (Near-Infrared) nanoprobes. Three representative NIR dyes could be successfully converted from hydrophobicity to hydrophilicity by entrapping them into the core region of the block copolymer micelles. All three samples showed small and uniform size distribution at35nm and good solubility in water. The fluorescent properties of the three fluorescent molecules in aqueous solution were therefore dramatically improved through the encapsulation, and their Stokes shifts were also enlarged. Finally, by grafting targeting molecules (Folic acid and Lactobionic acid) on the surface of the fluorescent nanoprobes, the NIR nanoprobes were synthesized with specific cell targeting capability. The in vitro cytotoxicity tests showed insignificant cytotoxicity, and in the functionalized nanoprobes were found capable of effectively targeting toward MCF-7and HepG2cells during a few hours as revealed by confocal laser scanning imaging.The present approach presents a general synthetic strategy for obtaining fluorescent nanoparticles with high and stable fluorescent efficiency, and promising application potentials for future biomedical applications.