The Construction And Functional Research Of Peptide-lipid Nanoparticles

Liposomes mimic the natural membrance and have excellent biocompatibility, so they are good carriers for a variety of drugs. With the development of liposomes, various lipid nanoparticles mimicking natural transport vehicles become more and more attractive. Firstly, the thesis introduces the mainstream methods in surface modifications of traditional liposomes and their drawbacks, followed by an overview of current progresses in the field of lipoprotein and peptide-lipid nanoparticles in detail. Secondly, the thesis presents my main research work on the assembly and functional study on peptide-lipid nanoparticles:(i) A bivalent peptide is designed to construct peptide-lipid nanoparticles platform, which can achieve nanoparticle formation, surface functionalization and hydrophobic drug loading in an integrated assembly process.(ii) A cationic amphipathic peptide is choosed to assemble the peptide-lipid nanoparticles to explore the optimization for its property. Lastly, I summarize my research work and give the future study direction. Below are the brief summaries of the main research projects included in the thesis.1. Construction of multi-functional peptide-lipid nanoparticle and research its function for targeted cell deliveryWe report a peptide-lipid nanoparticle assembly platform that achieves nanoparticle formation, surface function-alization and hydrophobic drug loading in an integrated fashion. A designer peptide that harbors bivalent amphipathic α-helices linked by a central loop(ALA peptide) is used to encapsulate lipid nanoparticles(LNPs). The bivalency design affords higher peptide helicity and lipid-packaging efficiency, and allows encapsulated hydrophobic molecules for more stability under long-term storage. The central loop structure displays sufficient surface exposure as demonstrated by the interaction between penta-histidine installed LNPs and Ni-NTA agarose. RGD-inserted and cytotoxic iridium complex-encapsulated LNPs show preferential entry and selective cytotoxicity to integrin high expression cancer cells,while showing reduced toxicity to non-cancer cells. Further study indicates that a constrained cyclic conformation of RGD is required to fully exert targeting capability, suggesting an intact structural exposure on the LNP surface.2. Construction of cationic amphipathic peptide-lipid nanoparticle and evaluation its cytotoxicity and stability in vitroWe choose cationic amphipathic R peptide(RLARLLRRLARWLR) to construct the peptide-lipid nanoparticle. R peptide could interact with lipid emulsion to promote the formation of lipid nanoparticles. And the hydrophobic amino acids of R peptide are inserted in the hydrophobic core of lipid nanoparticle to induce blue shift of tryptophan fluorescence. The R peptide-lipid nanoparticle(R-LNP) is monodispersed and has uniform size which diameter was 14.7±0.1 nm and zeta potential was 17.8 m V. Further, the cytotoxicity of R-LNP is studied through MTT assay. The results show the cytotoxicity of R peptide is retained in R-LNP, of which half-inhibitory concentration for A549 and MCF-7 was 5.93±0.75 μM, 4.36±0.40 μM respectively. Lastly, UPLC results demonstrate that R-LNP increases the stability of R peptide against chymotrypsin and trypsin, facilitating its translational application in vivo.