Preparation Of Polymeric Liposome And Its Preliminary Application In Drug/gene Delivery System

One of the most critical challenges in treatment is the construction of an efficient delivery system. In this dissertation, octadecyl-quaternized lysine modified chitosan (OQLCS) and its derivatives were synthesized successfully. Based on these polymers, polymeric liposome nanoparticles were designed and prepared successfully. It can be used as a multi-functional platform for drug / gene delivery system. The details are as follows:1) The synthesis of the octadecyl-quaternized lysine modified chitosan (OQLCS) and its derivatives. OQLCS and its derivatives were synthesized from chitosan, lysine, quaternary ammonium salt, PEG, folate and so on. The structure and properties were studied by FITR, fluorescence spectrum and so on. The results show that OQLCS and its derivatives were prepared successfully; OQLCS can self assemble into micelles in water due to its amphiphilicity; The OQLCS exhibited excellent solubility both in water and some organic solvents. The synthesis of OQLCS and its derivatives work as the materials for the preparation of polymeric liposome.2) The preparation of polymeric liposome and its application in drug delivery. The polymeric liposomes were synthesized from OQLCS and its derivatives. The properties such as particle structure, size, zeta potential, stability and cell uptake were studied. The results show that the polymeric liposome were nanospheres with with small size (effective diameter: 163.5 nm) and narrow distribution (polydispersity: 0.108) in aqueous solutions. The polymeric liposome could form multi-lamellar structure similar to that of conventional liposomes prepared from phosphatidylcholine/cholesterol (PC/Chol). Compared with traditional liposome, calcein-loaded polymeric liposome exhibited high encapsulation efficiency in aqueous solution and slow, controlled release under different pH conditions. PLs could be stored at different temperature (25, 4, and 20oC) and different medium (deionized water, phosphate-buffered saline and human plasma solution) for up to 4 weeks without significant size change. The spectrophotometer fluorometry analysis and the flow cytometry analysis indicated that in comparison with CL, PLs with positive zeta potential facilitates the uptake of calcein by MCF-7 tumor cells. 3) The preparation of magnetic polymeric liposome anchored with TAT for for crossing the blood-spinal cord barrier. TAT-conjugated PEGlated magnetic polymeric liposomes (TAT-PEG-MPLs) formed from PEGlated OQLCS, cholesterol (Chol), superparamagnetic nanoparticles, and transactivating-transduction protein (TAT), were prepared successfully and evaluated the properties in vitro and in vivo. The result indicated that TAT-PEG-MPLs were spherical in solution, with significantly small mean diameter (83.2 nm) and excellent magnetism (magnetization saturation values 43.5 emu/g). In vitro experiment, the uptake of PEG-MPLs with TAT by MCF-7 cells was greater than that of the PEG-MPLs without TAT. Most importantly, in vivo experiment, a low MRI signal was observed in the T2-weighted images; histological analysis revealed that TAT-PEG-MPLs nanoparticles significantly accumulated around the site of the SCI even inside the nerve cells.4) The construction of PLGA/polymeric liposome for targeted drug and gene co-delivery. The cationic PLGA/folate coated PEGlated polymeric liposome core-shell nanoparticles (PLGA/FPL NPs) were prepared. It was self-assembled from a hydrophobic PLGA core and a hydrophilic folate coated PEGlated lipid shell for targeting co-delivery of drug and gene. Hydrophobic drugs can be incorporated into the core and the cationic shell of the drug-loaded nanoparticles can be used to bind DNA. The drug-loaded PLGA/FPL NPs/DNA complexes offer advantages to overcome these problems mentioned above, such as co-delivery of drugs and DNA to improving the chemosensitivity of cancer cells at a gene level, and targeting delivery of drug to the cancer tissue that enhance the bioavailability and reduce the toxicity. The experiment showed that nanoparticles have core-shell structure with nanosize, sustained drug release profile and good DNA-binding ability. Importantly, the core-shell nanoparticles achieve the possibility of co-delivering drugs and genes to the same cells with high gene transfection and drug delivery efficiency.5) Folate-targeting magnetic core-shell nanocarriers for selective drug release and imaging.Superparamagnetic iron oxide nanoparticles (SPIONs) and doxorubicin (DOX) are co-encapsulated into PLGA/polymeric liposome core-shell nanocarriers for achieving simultaneous magnetic resonance imaging and targeting drug delivery. The core-shell nanocarrier was self-assembled from a hydrophobic PLGA core and a hydrophilic folate coated PEGlated lipid shell. The experiment showed that folate-targeting magnetic core-shell nanocarriers (FMNs) show clear core-shell structure, excellent magnetism and controlled drug release behavior. The core-shell nanoparticles achieve the possibility of co-delivering drugs and SPIONs to the same cells for enhancing magnetic resonance imaging (MRI) effect and improving drug delivery efficiency simultaneously.In this study, polymeric liposome, a kind of modularized platform technology, can self assemble into different delivery system according to demand. All the experiment results provided important experimental basis for the application of polymeric liposome in future.