Fabrication Of Conjugated Amphiphilic Block Copolymer For Drug Delivery And Fluorescence Cell Imaging

Cancer,as a major disease,is a serious threat to human health.At present,the main treatment methods of cancer,such as radiotherapy,chemotherapy and surgical treatment,have encountered some difficulties in clinical practice,which makes the treatment effect of cancer undesirable.Nanoparticles with smaller size,can be more gathered at the tumor site through EPR effect,therefore nanoparticles has potential value in cancer diagnosis and treatment.Amphiphilic block copolymer containing hydrophilic and hydrophobic chain segments at the same time,in the solution with a certain concentration can self-assemble to form micelles,which have the unique core-shell structure and have attracted widespread attention in the field of nano drug delivery system.An elegant integration of light-emitting segments into the structure of drug-loaded polymer nanoparticals endows its the ability of diagnosis.The conjugated polymers such as phenylacetylene,polythiophene,polyphenylene,polyfluorene,etc.,have potential application value in the construction of drug-loading system,because of their excellent fluorescence performance and light stability.Polyfluorene(PF)is known as a high-performance conjugated polymer with excellent chemical and thermal stability.Unfortunately,most PF derivatives are only soluble in the organic solvents,which apparently limits their applications in a water-based biological environment.To get the amphiphilic block copolymer especially triblock copolymer with polyfluorene as the hydrophobic segment,faces many challenges in the synthesis.In this dissertation,we have prepared the amphiphilic diblock copolymers containing polyfluorene segments,and studied the drug load ed and luminescence behavior of polymer micelles.O n the other hand,we have prepared the amphiphilic triblock copolymers containing polyfluorene segments,and studied the drug loaded and releasing behavior,luminescence behavior and cell imaging performance of the polymer micelles.In addition,we also prepared a temperature sensitive amphiphilic triblock copolymer containing polyfluorene.Specific research contents and results are as follows:1.Suzuki coupling condensation polymerization,atom transfer radical polymerization(ATRP)and click reactionwere conducted to prepare the target amphiphilic diblock copolymerPF-b-POEGMA.We prepared the drug loaded micelles and studied its drug-loaded capacity.TEM and DLS were performed to studied the morpholopy and hydrodynamic diameter of the micelles.In addition,we studied the fluorescence quantum yield of the polymer in water and THF by UV-vis and FLspecture.The results revealed that,the drug-loaded capacity of the micells was not satisfactory because of the short hydrophobic chain.In addition,the fluorescence quenching results in poor luminescence performance of polymer micelles due to the tight arrangement of polyfluorene chains in micellar nuclei.Combining the above results,the polymer is not suitable for the use in theranostic system due to the limitation of drug-loading capacity and fluorescence performance.2.On the basis of the previous work,we introduced PC L into the block copolymer,and synthesized the amphiphilic triblock conjugated polymer PF-b-PCL-b-POEGMA.Successful synthesis of polymers was verified by ~1 H NMR and GPC.We prepared the drug loaded micelles and studied its drug-loaded capacity and releasing behavior under different pH conditions.We studied the fluorescence quantum yield of the polymer in water and THF by UV-vis and FLspecture.In addition.Cell imaging properties of the polymer micelles in He La cells were studied by fluorescence confocal microscopy.In an aqueous phase,PF-b-PCL-b-POEGMA triblockcopolymers can self-assemble into core-shell-corona micelles.The PC L middle layer endows the micelles with not only a larger reservoir for drug loading but an improved fluorescence quantum yield(?)of 0.22 in water.The self-assembled fluorescent micelles could be efficiently internalized by HeLa cells with good biocompatibility for fluorescence imaging.Combining the in vitro cytotoxicity of DOX-loaded micelles against the cells,the conjugated amphiphilic triblock copolymers developed herein will provide new avenues for the design and synthesis of theranostic nanocarriers with strong fluorescence forimaging-guided cancer therapy.3.According to the synthetic path explored in the previous two systems,amphiphilictriblock conjugated polymerPF-b-PNIPAAm-b-POEGMA were synthesized.The successful synthesis of polymers was verified by ~1 H NMR and GPC.The thermo-induced association behaviours were investigated by DLS.