Preparation,Photophysical Property Enhancement And Biological Application Of Cyanine-Doped Silica Nanoparticles

Near-infrared cyanine dyes and their doped fluorescent silica nanoparticles have excellent photophysical properties,and are widely used in biofluorescence imaging and photodynamic therapy(PDT)of cancer.However,near-infrared cyanine dyes have large self-aggregation tendency and poor photostability in water,which affect the effect of fluorescence imaging and PDT.Therefore,a series of fluorescent silica nanoparticles doped with heptamethine cyanine dyes were developed to enhance their photophysical properties and make them more suitable for biofluorescence imaging and PDT.Four kinds of nanoparticles FSNP-1,FSNP-2,FSNP-3 and FSNP-4 encapsulated with cyanine dyes with different numbers of covalent binding sites were prepared by reversed-phase microemulsion method.In vitro and in vivo experiments show that their fluorescence brightness and photostability are directly related to the numbers of covalent binding sites.It is verified that FSNP-4 doped with cyanine dyes with three covalent binding sites can achieve long-term,stable and high-brightness fluorescence imaging through systematic in vitro and in vivo experiments.Three kinds of cyanine dye-dopted fluorescent silica nanoparticles FSNP-A,FSNP-B and FSNP-C were prepared via reversed-phase microemulsion method,which were based on the structure optimization of cyanine dyes and the local hydrophobic cage constructed in the nanoparticles by using octyltriethoxysilane(OTES).The combined strategy strengthened the fluorescence brightness,photostability and singlet oxygen(1^O₂)generation ability of nanoparticles in aqueous medium.Through laser confocal experiment,it is verified that FSNP-C modified with silane coupling agent OTES and doped with cyanine dyes with three steric groups and covalent binding sites can perform long-term,high-brightness fluorescence imaging and efficient PDT in 2D and 3D HeLa tumor cell models."Three-in-one" functional silica nanoparticle FSNC doped with 1^O₂ generating unit(protoporphyrin),1^O₂ storage and release unit(2-pyridone)and 1^O₂ self-monitoring unit(Cy7 cyanine dye)were prepared by reversed-phase microemulsion method.Under light irradiation,the 1^O₂ generating unit can generate 1^O₂ for the traditional PDT process,while the 1^O₂ storage and release unit can form the internal epoxide to storage 1^O₂.After terminating light irradiation,the pyrolysis of internal epoxide can release 1^O₂ to continue killing tumor cells,and achieve the fractional PDT process.The fractional PDT process can be traced by fluorescence imaging via the 1^O₂ self-monitoring unit.Through PDT experiment of HeLa cells,it was verified that FSNC can realize the fluorescence imaging-mediated fractional PDT process and strengthen the PDT effect.4-Amino-TEMPO was introduced into the cyanine dye structure to synthesize the near-infrared photosensitizer Cy7-TEMPO with a long triplet excited state lifetime.Then this type of photosensitizer was doped into silica to obtain the nano-photosensitizer FSNP@Cy7-TEMPO by reversed-phase microemulsion method.Because the electron spin polarization of 4-amino-TEMPO promotes the intersystem crossing(ISC)process,Cy7-TEMPO obtains a long triplet-state lifetime of 9.16 ?s and a relative 1^O₂ quantum yield of up to 0.20.When prepared into nano-photosensitizer,the triplet-state lifetime and relative 1^O₂ quantum yield have been generally improved.Meanwhile,the photostability of nano-photosensitizer has been significantly improved.PDT experiments on 2D and 3D HeLa cell models have verified the great application potential of FSNP@Cy7-TEMPO as a highly efficient near-infrared photosensitizer.