Synthesis And In Vivo/Vitro Bioimaging’s Study Of Carbon Dots Probes

Carbonaceous nano spherical（<10 nm）particles,also named as quantum carbon dots（CDs）,are novel nanomaterials applied in various filed in environmental protection,energy conservation and biomedical application.CDs are potential to be the alternative to substitute heavy metal elements containing toxic quantum dots due to their good chemical stability,photo-stability and biocompatibility.However,the drawbacks of CDs,including low quantum efficiency,optical intension dispersion et al.,are still worrisome to the researchers.CDs’fluorescent properties including photoluminescence（PL）intensity,excitation maximum(λ_ex)and emission maximum(λ_em),which are dependent on their size and surface modification,can be optimized by controlling reaction condition and choosing different carbon sources.And the surfacal functional groups of CDs including carboxyl and amino can interact with target molecule to implement CDs’tumor targetting bioimaging.Phenylenediamines,an important precursor for many heterocyclic compounds and polymers,of which three isomers have already been used to synthesize multicolor CDs,shows great pontential in the field of bioimaging nanotechnology.In this thesis,preparation and preliminary applications of luminescence probes were studied using phenylenediamines as the major carbon sources,and the thesis could be divided into two parts:1.Citric acid（CA）covered core-shell carbon dots were synthesized by two-step-hydrothermal method,which used isomers of phenylenediamine（oPD,mPD and pPD）to synthesize carbon core at first and added citric acid（CA）to continue carbonize by hydrothermal method.As-preapred CDs（OP-CCDs,MP-CCDs and PP-CCDs）were high Citric acid（CA）covered core-shell carbon dots were synthesized by two-step-hydrothermal method,which used isomers of phenylenediamine（oPD,mPD and pPD）to synthesize carbon core at first and added citric acid（CA）to continue carbonize by hydrothermal method.As-preapred CDs（OP-CCDs,MP-CCDs and PP-CCDs）were high fluorescence quantum yield（FLQY）probes.Compared to carbon core（C1,C2 and C3）emitted green,bue and red fluorescence under excitation of UV-vis light,whose FLQY were 10.4%,4.8%and 10.6%,OP-CCDs,MP-CCDs and PP-CCDs all emitted high quantum yield（QY）blue fluorescence（FLQY>50%）.Cells experiments in vitro showed that CDs can be rapaidly internalized by NIH-3T3 cells.In addition,fluorescence images in vivo showed that after intravenous injection for 6 hours,the CDs aggregated at the bladder and the kidney and bioimaged.CDs can rapaidly excreted through urinary,avoiding tissue damage caused by material’s long-time aggregation.2.Folate acid（FA）doped carbon dots were synthesized by hydrothermal method,cancer-targeted multicolor fluorescence probes OF-CDs,MF-CDs and PF-CDs were produced by mixing three isomers（o-phenylenediamine（oPD）,m-phenylenediamine（mPD）,and p-phenylenediamine（pPD））with FA.OF-CDs,MF-CDs and PF-CDs emitted green,blue and red fluorescence under the excitation of an UV-vis laser（FLQY=12.2%,13.1%and10.1%）.Cells experiments in vitro showed strong cancer cell targeted ability and good biocompatibility of CDs.Fluorescence images in vivo showed that after intravenous injected through mice tail vein,PF-CDs can aggregate at the Hela cancer tissue through the blood circulation within 15min and continue imaging for 40 min.In this thesis,CDs with different functions are prepared through hydrothermal method,and proved to be biocompatible and can be rapidly excreted.CDs’ability of targeting to cancer cells was obtained by doping FA,which optimized CDs’application in bioimaging field.