Synthesis And Biological Applications Of Benzothiadiazole And Tetraphenylethylene Fluorescent Derivatives

Real-time and long-term tumor cell tracking is of great importance for cancer diagnosis and improvement of therapeutic outcomes.The key technology lies in exploring the high performance fluorescent probes.However,the present fluorescent probes still suffer from low fluorescence quantum yields,small Stokes shifts,poor photostability,weakened or quenched fluorescence in aggregated state and high cytotoxicity.As a consequence,these defects would limit their further utilities in biological applications.Hence,we designed and synthesized a series of fluorescent derivates based on benzothiadiazole and tetraphenylethylene.We investigated the effect of substituent and molecular structure on the photophysical properties and recognition performance of the fluorescent probes and obtained the mechanism.In addition,these fluorescent probes were applied in recognition of biological molecules,real-time cell tracking in vitro and tumor growth in vivo.(1)We firstly synthesized a novel cationic fluorophore based on benzothiadiazole(PPB),characterized by nuclear magnetic spectra,high resolution mass spectra,infrared spectra and element analysis and studied the photophysical properties.It depicted a large Stokes shifts(~155 nm),which can effectively avoid the interference of background fluorescence and achieve high signal-to-noise ratio.It also exhibited high fluorescence quantum yields,superior photostability and low cytotoxicity.These remarkable properties make PPB as an ideal candidate for applications in real-time and long-term tracking.In vitro results demonstrated that PPB could track HeLa cells division up to 16 passages and the cells showed normal morphology and healthy growth.In vivo results displayed PPB could effectively monitor tumor growth for 27 days.Additionally,the ex vivo and H&E results further demonstrated the good biocompatibility of PPB.As a consequence,PPB can be used as a promising long-term tracker.(2)The fluorescent probes with red emission are more suitable for application in vivo.We introduced the furan unit to modify the benzothiadiazole,synthesized a novel RNA-selected red emissive(605 nm)cationic fluorophore(PFB)and applied in real-time and long-term tracking in live cells and living organisms.PFB could act as a fluorescent probe for cellular imaging with high uptake efficiency and highly sensitive detection toward RNA under low optimum concentration(1 uM),which enabled it to achieve cancer cell tracing in vitro and tumor growth monitoring in vivo.The results of real-time tracking experiment revealed that PFB can be traced in stained HepG-2 cells for 11 generations and monitor tumor growth for 18 days.Therefore,PFB was expected to be widely used in gene expression,disease diagnosis,such as the physiological processes involved in miRNA,and image-guided surgery.(3)We further introduced the thiophene ring to modify the benzothiadiazole and synthesized a novel far-red emissive(625 nm)cationic fluorophore(PTB).PTB was applied as a promising nucleus-targeted fluorescent probe with a 73.8-fold enhance in fluorescence when bound to DNA and real-time and long-term tracking in live cells and living organisms.PTB exhibited a large Stokes shifts(~110 nm),low cytotoxicity and good photostability.The CLSM images suggested PTB could rapidly penetrate the live cells and specificity stain the nucleus.The real-time and long-term tracking results demonstrated that PTB could efficiently trace HepG-2 cells division up to 11 generations in vitro and monitor tumor growth for 21 days in vivo.Apart from that,the ex vivo,H&E staining and immunofluorescence FITC staining results further proved the biocompatibility of PTB.As a consequence,PTB has a great application outlook in prospective tracing for the replication,transcription and expression of disease at the genetic level.(4)In order to elevate the HOMO level of the fluorescent probe,we modified the TPE core with phenothiazine and synthesized a novle AIE-active near-infrard fluorescent probe,TPE-PTZ-R.The energy gap(Eg)of the fluorescent probe was significantly reducted,which accompanied with the redshift of the absorption and emission of the fluorescent probe.We investigated the solvatochromism and AIE features of this novle near-infrared fluorescent probe.Then,we fabricated the uniform and stable AIE nanopaticles by loading Pluronic F127 and apply it in cellular bioimaging with high uptake efficiency,low cytotoxicity and good photostability.These results demonstrate that these near-infrared fluorescent nanoparticles can be used as a potential fluorescent material in the field of biology.