Design Of Biological Environment Responsive Perylene Carboximide Probes And Their Biomedical Applications

Owing to the high resolution and facile visualization features,fluorescent imaging technique has been developing rapidly.Organic dyes equipped with multi-modification sites,tunable optical properties and high biocompatibility played a more and more important role in molecular imaging and biomedical applications.Perylene carboximide including perylene diimide(PDI)and perylene monoimide(PMI)possess many good characteristics such as ultrahigh stability,multi-modification sites,high fluorescent quantum yield and tunable optical properties.Taking advantage of these features,perylene carboximide was widely applied in biomedical fields.For example,PDI based polymers were used for gene,protein and drug delivery.Specifically modified PDIs were adopted for cancer photodynamic and photothermal therapy.However,biological environment is very complicated equipped with many biological barriers and materials with monotonous characteristics were hard to cross these barriers.Thus,designing stimuli-responsive materials is imperative.Aiming at developing perylene carboximide based fluorescent agents for biological environment responsive applications,the following issues should be considered.(1)Poor water solubility and aggregation induced fluorescence quenching(2)High stability led to insensitivity to biological environment(3)Difficult to achieve huge fluorescence change.Therefore,improving these aspects would offer new chances for perylene carboximide in biomedical applications.For instance,to address the aggregation and fluorescence quenching issues,perylene carboximide was modified with polymer,dendrimer or functional groups to achieve excellent water solubility,biocompatibility and high fluorescence emission intensity.Through the introduction of stimuli-responsive groups or guest molecules,perylene carboximide would exhibit fluorescence signal change after corresponding stimulus was applied.In this thesis,PDI and PMI with ultrahigh stability was chosen as the chromophore and different design strategies were adopted to achieve biological environement response.The main contents were summarized as follows.Firstly,through the pH triggered disassembling process of perylene carboximide dyes with guest molecule,the guest molecule release was monitored with fluorescence "turn-on".Secondly,pH and reductive environment responsive polymers were introduced to perylene carboximide chromophore,which realized enhanced cellular uptake and drug delivery upon tumor microenvironment stimuli.At last,multi-organelle discrimination and 3D imaging were realized by PMI with multi-organelle targeting groups and pH activatable functional group.To conclude,we have designed and synthesized a series of biological environment responsive fluorescent probes based on PDI and PMI.Through self-assembling technique,these probes were made into nanomaterials and further used for biological environment activatable release monitoring,anticancer studies and multi-organelle discrimination.The major contents of this thesis were as follows:1.Four armed amphiphilic block co-polyphenylalanine-polylysine(PPL)was synthesized through ring-opening polymerization with PDI based initiator.The obtained polymer showed good water solubility and high fluorescence intensity.Hydrophobic drug curcumin was encapsulated within the polymer to achieve supramolecular drug delivery system.However,the fluorescence of PDI quenched immediately upon curcumin encapsulation.Through fluorescence spectroscopy,theoretical modeling and electrochemical testing,the fluorescence quenching mechanism was identified to be photo induced electron transfer.Upon acidic stimulus,curcumin could be released and fluorescence of PDI "turn-on",which demonstrated the drug release process.Thus,taking advantage of photo induced electron transfer process,high contrast drug release monitoring system was within reach,affording more design strategies for advanced biomedical research.2.Star cationic polylysine was prepared with four armed PDI-based initiator with amino groups dangling in the side chains.Antitumor drug camptothecin was attached to the polymer through tumor reductive microenvironment labile bond to obtain P1.Another polyanions P2 was synthesized with tumor acid responsive bond.Supramolecular drug delivery system was constructed through the complexation of P1 and P2.The prodrug P1@P2 armed with dual-stimuli responsive properties could self-assemble into rod-like nanoparticles with a size of 150 nm.Upon entering the tumor periphery,P1@P2 underwent charge-conversion in the prescence of weak acid and exhibited enhanced cellular uptake and subsequently camptothecin was release under reductive environment.Both in vitro and in vivo experiment verified high antitumor efficiency of the supramolecular drug delivery system.Thus,this fluorescent supramolecular drug delivery system offered a platform for tumor microenvironment responsive design and programmed drug delivery.3.A novel PMI based fluorescent probe was developed for multi-organelle discrimination with large absorption/emission band change.The probe was equipped with the following functions.(1)Lysosome targeting group(2)mitochondria targeting group(3)PMI without bay substitution,which is a cell nucleus targeting moiety(4)pH activatable switch that hydrolysis in mitochondria and exhibited over 100 nm absorption/emission band change.Owing to the multi-polar groups introduced,the probe has good water solubility(>10 mg/mL)with absorption/emission band at 490 nm and 570 nm,respectively.In vitro studies identified the probe could be rapidly uptake by HeLa cells within 3 min and preferentially localized in lysosome with the green channel.Then,the probe was transferred into mitochondria and hydrolysis to release NIR emission.At last,the NIR emission could also be found in the cell nuclei.After 100 min,the lysosome was green,mitochondria was yellow due to the overlap of green/NIR channel and cell nuclei was red.Thus,multi-organelle discrimination was realized with one probe and three color and 3D imaging also demonstrated the different location of these organelles.To conclude,our design provided a new method to develop biological environment responsive probe.