Design,Synthesis and Applications of Functional Squarylium Indocyanine Dyes
Author:Ji Chen Dong
Supervisor:yin mei zhen
With the rapid development of fluorescent techniques,fluorescent imaging agents and sensors based on organic dyes have been extensively used in environmental and biological fields.Owing to the large molar extinction coefficient,high fluorescent quantum yield,tunable absorption/emission band within a wide range from visible to near infrared(NIR)region and multi-modification site,cyanine dyes have attracted enormous attention and were widely studied.For instance,ICG,as a kind of cyanine dye,has been approved by American Food and Drug Administration for clinical imaging applications.However,traditional cyanine dyes have defects such as poor photostability and strong aggregation tendency,resulting in self-quenching and measurement error,which might decrease the detection sensitivity to a great extent and impede their advanced biomedical applications.Thus,improving or taking full advantage of these characteristics of cyanine dyes for new design strategies is critical for widening their application fields.For example,aggregation of cyanine dyes leads to fluorescent quenching,but,controllable aggregation might bring about new performance.In this thesis,we chose squarylium indocyanine dye with good photostability as the chromophore.By using different modification strategies,we achieved functionalization and controllable self-assembling of cyanine dyes.The properties of these functional dyes were as follows:(1)The aggregate of cyanine dye was sensitive to ammonia and ammonia sensing was realized through optical signal changes.(2)Controllable self-assemble of cyanine dye gave rise to the formation of regular nanoparticles,which showed better bioavailability.(3)The aggregation of cyanine dyes caused improved photodynamic performance,which induced cytotoxicity upon light irradiation.Based on the above mentioned properties,we designed a series of functional cyanine dyes and subsequently regulated their assembly properties to obtain several cyanine-based nanomaterials.These nanomaterials were applied for environmental and biomedical fields.The research contents were summarized as follows:1.We reported a flexible naked eye ammonia sensor,the PLA-Cy fibrous mat,which was fabricated by blending a carboxyl-functionalized cyanine dye(DI)into polylactic acid(PLA)through electrospun.The sensing mat undergoes a naked eye detectable color change from white to blue upon exposure to ammonia vapor.The mat showed high selectivity to ammonia gas with the detection limit of 3.3 ppm.The sensing mechanism was elucidated by the self-assemble to de-assemble process of D1.Aggregated D1 was first encapsulated by PLA,and upon ammonia fuming,D1 was ionized,leading to de-aggregation.These mechanisms were examined by photophysical studies and scanning electron microscopy(SEM).This ammonia sensor mat based on aggregation of cyanine dyes provided new ideas for gas sensors.2.A novel amphiphilic squarylium indocyanine(LysoCy)was reported for remarkable lysosome tracking in living cells.LysoCy performed as a promising lysosome tracker with low cytotoxicity,strong binding affinity and clear subcellular labelling.Owing to the amphiphilic property,LysoCy self-assembled to form nanovesicle in aqueous solution.LysoCy underwent rapid cellular uptake though endocytosis and then localized in the lysosome.In vitro experiment indicated that compared with commercially available LysoTracker,LysoCy labelled lysosome specifically as well.Long-term dynamics of lysosomes was revealed by LysoCy up to 2 day’s culture,while the working duration of commercial dye was no longer than 1.5 hours.Furthermore,optical and ITC measurements demonstrated that both electrostatic and hydrophobic interaction played important roles in the labelling process.Thus,our research proved that LysoCy could be applied in long-term tracking of lysosome,which widened the application of cyanine dyes.3.We designed and synthesized a novel cyanine prodrug ICy5-CPT-RGD with anticancer drug and targeting group covalently attached to both sides of cyanine dye.ICy5-CPT-RGD self-assembled in aqueous solution to form nanodrug PTN,which achieved effective cancer theranostics.The self-assembled nanodrug had small assembly size(ca.90 nm),good stability,long wavelength emission,significantly enhanced photodynamic efficiency and good tumor targeting ability.Moreover,PTN also had stimuli-responsive properties.Upon lysosome acid and subsequent photo stimuli,PTN rapidly deconstructed into ultrasmall nanoparticles(ca.5 nm),resulting in accelerated drug release.In vitro and in vivo experiments were conducted to verify the photodynamic ability,drug release,deep tumor penetration,in vivo fluorescent imaging and good biocompatibility of PTN.At last,PTN was adopted for cancer chemo-photodynamic combined therapy,which exhibited potent inhibition efficiency of tumor.Therefore,we offered a non-chemical approach to elevate the photodynamic effect of cyanine dyes and achieved dual stimili-responsive drug release,which provided new insight for the preparation of multi-functional cyanine dyes.