Construction Of Near-infrared Ⅱ Fluorescent Molecule And Its Study On Fluorescent,Photoacoustic And Phototherapeutic Properties

Malignant tumor has posed a threat to human health.Fluorescent imaging in the second near-infrared window（NIR-II,1000-1700 nm）and photoacoustic imaging hold deeper penetration depth,higher sensitivity,resolution and signal-to-background ratio when compared to fluorescent imaging in the first near-infrared window（NIR-I,750-1000 nm）,which contributes to more accurate imaging analysis and diagnose.Closely related to optical imaging,phototherapy benefits precise therapy owing to its spatio-temporal controllability,non-resistance and negligible side-effect.In situ diagnostic and therapy are allowed to concurrently occur when NIR-II optical imaging and phototherapy are integrated into one NIR-II fluorescent molecule.This will facilitate real-time monitoring for tumor progress,accurate diagnostic and therapy.Nevertheless,the development of such multifunctional phototheranostic NIR-II organic molecules are still hindered by lacking instructive designing strategy.In view of the aforementioned limitations,two main issue should be considered:i)The wavelength of current NIR-II organic fluorophores with necessary stability are restricted in the shorter range(λ_abs<900 nm,λ_em<1200 nm),failing to avoid autofluorescent interference from the thick tissue such as brain and liver.ii)The multifunctionality of such NIR-II organic molecule comes from different energy dissipation pathways of the excited-molecule,which competes to each other and is difficult to regulate simultaneously.Focusing on the above issues,this dissertation initially aimed to develop NIR-II organic molecule with necessary stability and longer absorption and emission wavelength.Afterwards,regulation for different energy dissipation pathways was studied to construct multifunctional NIR-II organic molecule by specific structural engineering.Finally,the NIR-II organic molecules were applied into fluorescent and photoacoustic imaging guided phototherapy for tumor.The essential studies of this dissertation are sketched out as follow:i)By summarizing the effect on absorption and emission wavelength from different methods of extending conjugated backbone and various electronic donor and acceptor,three fluorescent organic molecules known as Hcy,SY and BBTD-1302were rationally designed and synthesized.Trough investigation of their photophysical properties,the NIR-IIa（1300-1400 nm）emissive molecule BBTD-1302 was chosen for fluorescent and photoacoustic imaging guided phototherapy of tumor.ii)Learn from the previous study,Aza-BODIPY scaffolded NIR-II organic molecule CCNU-1060 was constructed,which possessed multifunctionality known as NIR-II fluorescent imaging,photodynamic and photothermal therapy.Importantly,a strategy denoted as“rigidity bridging flexibility”was proposed to cure the contradiction that the multifunctional properties was obtained through offsetting from each other in different deactivation proccesses.