Novel BODIPY-based Fluorescent Dyes: Synthesis, Detection Of Small Biomolecules And Application In Photodynamic Therapy

Small reactive biomolecules including reactive oxygen species and biothiols are the important components to maintain the normal vital activity.However,the mistaken localization and abnormal level of these small biomolecules would be associated with some diseases.Hence,development of novel fluorescent probes to discriminate these small biomolecules and explore their application in living cells is very important.On the other hand,photodynamic therapy(PDT),a novel therapeutic approach for skin inflammation,bacterial infection,and malignant tumor,has attracted wide attentions due to its minimal invasiveness,low systemic damage,drug-resistance,high spatiotemporal precision,and easy administration.Photodynamic therapy calls for the photosensitizers to convert the molecular oxygen to the cytotoxic singlet oxygen upon light illumination.Hence,development of novel photosensitizers would be helpful in the research of photodynamic therapy.Boron dipyrromethene(BODIPY)was a promising fluorophore which contains numerous excellent merits such as high fluorescence quantum yield and molar extinction coefficient,narrow fluorescence emission,well biocompatibility,controllable structure modification,and near infrared emission.Herein,BODIPY could be developed as the fluorescent probes for small reactive biomolecules and photosensitizers for photodynamic therapy.In this article,a series of BODIPY-based fluorescent probes were displayed to detect small reactive biomolecules(NaClO,biothiols)and applied in living cells.In addition,some novel BODIPY-containing photosensitizers were introduced for photodynamic therapy and systematical biological eveluation was conducted.The main contents including seven parts were as follows:Part 1: Introduction.Firstly,this part introduced the structures,photophysical properties,and applications of some common small organic molecular fluorescent dyes and BODIPY-based fluorescent dyes.Secondly,the research of the fluorescent probes for small reactive biomolecules was introduced.Some representative BODIPY-based fluorescent probes for small reactive biomolecules were listed.Thirdly,this part introduced the mechanisms of photodynamic therapy(PDT)and reviewed the species and researches of photosensitizers based on small organic molecular fluorescent dyes.Several photosensitizers based on BODIPY and their PDT functions were listed.Lastly,the contents of this dissertation were summarized.Part 2: A near infrared(NIR)BODIPY-based fluorescent probe BODIPY-ONs for glutathione(GSH)was introduced.styryl-BODIPY was used as the NIR fluorescence core and 2,4-dinitrophenylsulfate was chosen as the GSH recognizer.2,4-dinitrophenylsulfate was linked with the hydroxyl of the phenol at the meso site of styryl-BODIPY.The probe could discriminate biothiols from other amino acids without sulfydryl group.Moreover,the probe showed higher response toward GSH than cysteine(Cys)and homocysteine(Hcy).According to the results from HPLC,HRMS,and theoratical calculations,a novel mechanism that hydrogen bond assisted thiolysis was proposed to verify the recognizing mechanism of the probe for GSH.The probe has been successfully used to detect endogenous and exogenous GSH;Part 3: A bithiols fluorescent probe BODIPY-S-Np which was constructed by two fluorophores system(BODIPY/ Naphthalene diimide)was introduced.The sulfydryl-containing naphthalene diimide was combined with BODIPY at its 5-site with the thioether bond.The probe could discriminate Cysteine,Homocysteine,and glutathione with different response phenomena.Specifically,after identifying cysteine,the probe displayed the enhanced green fluorescence.The probe displayed dual emission(blue/orange)and ratiometric fluorescence increasement to recognize GSH.In weakly acidic solution,probe displayed orange fluorescence response toward Hcy.In neutral solution,probe showed green fluorescence.The ratiometric fluorescence response could eliminate the interference from instruments and displayed high sensitivity.Hence,compared with Cys and Hcy,the detection limit of probe for GSH was very low to 3.3 nM.The probe could detect the exogenous Cys and Hcy in living cells with the fluorescence enhancement and response endogenous and exogenous GSH with ratiometric fluorescence enhancement.Part 4: A red emissive BODIPY-based fluorescent probe avyl-BODIPY-PTZ with ratiometric response for NaClO was introduced.The probe constructed by the electron-donor phenothiazine and electron-acceptor styryl-BODIPY to form the orthogonal D-A structure.The probe could selectively and sensitively detect NaClO via the ratiometric fluorescence enhancement.The recognition mechanism of the probe for NaClO was NaClO induced the oxidization of phenothiazine to form the sulfoxide-type product.The dual emission of the probe was originated from the twisted intramolecular charge transfer(TICT).After reaction with NaClO,the TICT effect of the probe reduced and the emission ascribed to LE state surpassed the emission of TICT state.Hence,the probe could discriminate NaClO via a ratiometric fluorescence enhancement.At last,the probe was used to detect NaClO in living cells with two-channel fluorescence changes.Part 5: The photosensitizer BDPI-lyso used the diiodoBODIPY as the singlet oxygen generator and was modified with lysosome targeting group morpholine.The photosensitizer displayed high singlet oxygen quantum yield and pH-controlled singlet oxygen generation.The singlet oxygen quantum yield in acid solution was higher than in neutral solution indicating that the photosensitizer could display higher PDT effect in acidic organelle lysosome than in other neutral organelles.The photosensitizer could target lysosome in living cells and destroy the lysosome to induce the lysosome-associated cell apoptosis upon light illumination.Part 6: The electron-donor carbazole was combined with electron-acceptor BODIPY at its meso site to form an orthogonal D-A type photosensitizer Cz-BODIPY.The photosensitizer displayed excellent water solubility and photostability,high singlet quantum yield and low fluorescence quantum yield.The photosensitizer possessed low dark cytotoxity and high phototoxity and could generate singlet oxygen to induce cell apoptosis.The photosensitizer could be uptaken by zebrafish and generate singlet oxygen upon light illumination.Moreover,the photosensitizer could inhibit the migration of tumor cells after light illumination.In summary,the photosensitizer displayed the potential application in real photodynamic therapy.Part 7: In conclusion,many modification strategies were adopted to develop novel BODIPY-based fluorescent dyes.On the one hand,two biotiols fluorescent probe and one NaClO fluorescent probe were synthesized.The recognition effect,sensing mechanisms,and application potential in living cells of there probes were studied.On the other hand,a lysosome-targeting photosensitizer and an orthogonal D-A type photosensitizer were developed for photodynamic therapy.The PDT mechanisms and PDT effects of these photosensitizers were evaluated.