Preparation Of Biocompatible Organic Nanoparticles And Their Applications In Cell Imaging

It is well known organic dyes have been most widely applied in biological imagingin the past years, however, the problems of intrinsic hydrophobic property andaggregation induced fluorescence quenching also including instability inbio-environment place great restrictions on their utilization in long-term imaging. Withthe development of nanotechnology, various dye-nanocarriers such as silicananoparticles, carbon-based nanostructures and polymer micelles, are emerging.Through surface functionalization of carrier, biocompatibility, enhanced stability andresistance to photobleaching are realized. All those structures have very limiteddye-loading and relatively high carrier content that lead to high quantum yield and lowabsorption cross section per particle. However, brightness of the probes depends notonly on the quantum yield (QY), but also on the absorption of the dyes which meanshigh quantum yield and low absorption also result in low brightness. In the thesis,starting from the point of improved absorption by increased dye number per particle, weprepare carrier free organic dye nanoparticles and then after surface modification,biocompatible organic nanoparticles are used for cell imaging. We choose highlyfluorescent2-tert-butyl-9,10-di(naphthalen-2-yl)anthracene (TBADN) as researchobject.(1)150nm TBADN nanoparticles are first prepared by solvent exchangingmethod and then followed by surface modifications with amphipathic surfactant toachieve excellent water dispersity and bio-environmental stability. Pure dyenanoparticles possess large absorption area, up to15%quantum yield which lead tovery high brightness, thus organic nanoparticles is provided with comparable, if nothigher, brightness than CdSe/ZnS QDs. Furthermore, TBADN nanoparticles can also beconjugated with folic acid for targeted cell imaging.(2)For red emissive even longeremissive dyes, it has been shown that aggregation induced quenching is more severe. Tosolve the problem, doping technique is introduced by us. The TBADN nanoparticles are used as host and C545T, DCJTB are as acceptor, excellent fluorescent probes withhigh brightness, large Stokes shifts and tunable emissions are achieved throughfluorescence resonance energy transfer. The resulting optimum green emissive NPs gainhigh brightness with QY up to45%and12times AE, and red emissive NPs with QY of14%and10times AE. Similarly, through nonconvalent binding, surfacefunctionalization endow the doped NPs with excellent water dispersibility andoutstanding bio-environmental stability. Finally, we realize targeted cell imaging. Theabove results indicate that surface modified organic nanoparticles are entirely feasibleand have obvious advantages in cell imgaing, thus expected to be a new generation ofexcellent fluorescent probe.