Study On Preparation,Structure,Properties And Applications Of Multifunctional Drug-loaded Polydiacetylene Liposomes

Drug delivery system that combines disease diagnosis and therapy is very promising and urgently desired by modern medicine.The integration of drug carrier and tracer is the common method used for the disease diagnosis and therapy at the lesion site.However,due to the poor stability and biocompatibility,the clinical research and practical application of these theranostics are severely limited.Liposome is regarded as the most promising delivery vehicles in biotechnology and biomedicine applications.Liposome that possesses drug delivery and tracing properties has attracted more and more attention and being widely investigated and developed.Polymer liposome consisting of liposome and functional polymer is a very promising multifunctional drug carrier due to its excellent properties of stability,biocompatibility,controlled drug release,and fluorescence tracing.The dissertation concerns the forefront research area and establishes a basic research method to satisfy the urgent need of cancer treatment.The following work mainly focuses on the preparation and characterization of polydiacetylene liposome(PDA liposome),in particular on the physical,chemical properties and biological function as a multifunctional drug delivery system that combines drug tracing and controlled release.The work mainly includes the following contents:First:Preparation of PDA liposome.PDA liposome was prepared by a combination method of thin film evaporation and supercritical fluid of carbon dioxide(SCF-CO2)in this work.The traditional methods of thin film evaporation and ultrasound are used commonly to prepare PDA liposome.However,the stability of PDA liposome prepared by the traditional method is poor.In this work,the PDA-liposome prepared by the combination method of thin film evaporation and SCF-CO2 is more regularly arranged,and the size of PDA liposome is controllable and even distributed.Thus,the PDA liposome in this article is characterized with more stability.Second:PDA liposome with reversible fluorescence.In this work,PDA liposome with reversible fluorescence switch was presented for the first time.The reversible switch of fluorescence emission wavelength of PDA liposome was observed under heating and irradiation conditions,which had great potential in the application of biological detections.The optical properties and microstructures of PDA liposome were then investigated applying fluorescence/UV spectroscopy,dynamic light scarring(DLS),steady-state fluorescence probe method,Fourier infrared/Raman spectroscopy(IR/Raman spectroscopy),differential scanning calorimeter(DSC),and high resolution transmission electron microscopy(HRTEM).The results indicate that the reversibility associates with the micro structure of PDA liposome.The conjugation length and conformations of side chains of the polymer backbone change under different conditions,so that the size,lattice spacing and fluorescence of PDA liposome are varied correspondingly.Third:Structure,size,properties and functions of PDA liposome.1.Structure and size of PDA liposome.The structure,size,zeta potential,fluidity of membrane,information of polymer backbone,and fluorescence properties of PDA liposome prepared by a combination method of thin film evaporation and SCF-CO2 were studied.The results showed that PDA liposome was monodispersed and provided with good hydrophilicity and stability.2.Drug loading and control release of PDA liposome.Hydrophobic docetaxel and hydrophilic berberine were used as two model drugs loaded by PDA-liposome.The drug-loaded PDA liposome was synthesized by the combination method of thin film evaporation and SCF-C02.The drug efficacy and control release of PDA liposome were studied.Human breast cancer Bcap-37 cells were chosen as the model live cell to investigate the drug efficacy of PDA liposome.The results showed that the drug-loaded PDA liposome was characterized with high entrapment efficiency,low cytotoxicity,and good stability.The temperature-controlled drug release of PDA liposome was realized by in vitro analog device and live cancer cells.The results of cytotoxicity experiments showed that the drug-loaded PDA liposome was effective to inhibit and kill the cancer cells upon temperature-controlled drug release.3.Fluorescence imaging and fluorescence resonance energy transfer.The fluorescent PDA-liposome could trace the loaded drugs in vitro and in vivo,and it could provide a novel tool for drug monitoring and tracing in real time.Besides,the fluorescence resonance energy transfer(FRET)is realized between the berberine and PDA.The characteristic fluorescence emission wavelength of berberine is 547 nm,which is near the absorption wavelength of PDA(550 nm).As a result of FRET,the fluorescence of PDA is enhanced by the loaded berberine molecules nearby.And the intracellular distribution of released berberine could be traced according to the respective fluorescence emission wavelength.