博士申请用研究计划英文模板Word文件下载.docx

1、A. Proposed area of researchThe aim of this proposed PhD project is to develop and evaluate pH responsive, endosomolytic polymers for efficient intracellular delivery of biological drug payloads.There is a need to better understand the mechanisms of entry into the cell cytoplasm and nucleus in order

2、 to design optimal delivery systems for biological molecules. On the one hand, this would open up significant opportunities to deliver potent drug payloads against intracellular targets to positively impact human health. In addition the project aims to develop a more general understanding of the rul

3、es governing the uptake of biological molecules into cells.This project proposes to investigate the use of synthetic, biodegradable polymers for intracellular delivery of drug payloads （including siRNA, therapeutic peptide and antibody） against a well-validated intracellular drug target, such as Bcl

4、-2. The novel pH-responsive polymers have been designed by Dr Rongjun Chens Lab to mimic the activity of viruses, both in their cell entry and endosomal escape mechanisms. Using cancer cell lines （Jurkat or HL-60 cells） as a model system, the polymers would be tested with a variety of different biol

5、ogical payloads in a quantitative comparison of their ability to enter the cell and trigger apoptosis and subsequently cell death. With an efficient model system established, there would then be scope to optimize the system in terms of the kinetics and mechanisms of cell entry, cytoplasmic and nucle

6、ar localization, and the biodegradation of the polymers. There would also be scope to explore the efficiency in other cell systems and with further intracellular targets. This multidisciplinary project is at the interface of Chemistry, Biology and Medicine, and will provide the student with a real o

7、pportunity to be involved in the development and evaluation of new nanomedicines. B. BackgroundAdvances in genomics and proteomics have enabled the development of macrodrugs, such as nucleic acids and proteins, with potential for the treatment of a wide variety of diseases. Amongst other problems, t

8、heir clinical applications may be greatly impaired by low cellular uptake and lysosomal degradation before they can reach their target organelles or cell nuclei. In order to achieve efficient intracellular delivery of such biological molecules, delivery systems are required to enable high cell entry

9、 via endocytosis and efficient release into the cytoplasm by endosomal membrane disruption under mildly acidic conditions.Recombinant viruses and fusogenic viral peptides have been used to mediate gene transfection, but their clinical use is potentially limited by safety issues and difficulties in l

10、arge-scale production. A variety of synthetic polymers have therefore been developed as non-viral vectors. Cationic polyethyleneimine, poly（2-（dimethylamino）ethyl methacrylate） and polyamidoamine dendrimers mediate gene delivery through the proton sponge effect, but suffer from cytotoxicity and rela

11、tively low transduction efficiencies. The intensively studied vinyl-based anionic polymers, poly（a-alkylacrylic acid）s, display pH-responsive membrane disruptive behavior, but they are not biodegradable, thus low molecular weights have to be strictly required to allow renal excretion and their clini

12、cal applications are seriously limited. Dr Rongjun Chens Lab has recently developed a class of novel, biodegradable, pH-responsive polymers to mimic factors that enable efficient viral transfection, but they are safe, easy to manufacture and have more controllable structures. The parent polymer is a

13、 polyamide, poly（L-lysine isophthalamide）, which was based on polycondensation of diacyl chlorides and natural metabolite tri-functional amino acids containing both - and -amine groups. Hydrophobic amino acids and/or poly（ethylene glycol） were grafted onto its pendant carboxylic acid groups to manip

14、ulate its amphiphilicity and structure. The metabolite-derived biomimetic polymers can undergo pH-mediated coil-globule changes in conformation. This property enables these polymers to be significantly membrane-disruptive within pH range typical of endosomal compartments, but necessarily non-toxic a

15、t physiological pH. Based on previous successful intracellular delivery of the model-drugs such as calcein, dextran （with molecular weight ranging from 3kDa to 70kDa）, and therapeutic protein apoptin and siRNA, it is thought that these polymers may be able to deliver a wide variety of different biol

16、ogical molecules （nucleic acids and proteins） into cells for the treatment of various diseases including cancers. C. Applicants work preparation in ChinaThe applicant is an expected bachelor majoring in Polymer Science and Engineering from Beijing University of Chemical Technology （BUCT）. After four

17、 years of undergraduate studies （2007-2011）, I have obtained a strong research background in organic chemistry, polymer physics and chemistry, physical chemistry, etc. Working in the State Key Laboratory of Polymer Physics and Chemistry in the Institute of Chemistry of Chinese Academy of Science for

18、 more than half of a year has set up my mind in researching polymer drug carriers. Our group cast our eyes towards synthesizing graft copolymers with amino acids as the main monomers, to create a novel carrier which is both pH and temperature sensitive. We had synthesized a polymer brush from Z-lysi

19、ne and 2-Bromoisobutyryl bromide through ring-opening polymerization. Then we grafted specific temperature sensitive residues onto the polymer brush via atomic transfer radical polymerization, followed by characterization and theoretical analysis of the polymers. In addition, I was a Research Assist

20、ant in the state key laboratory of Beijing University of Chemical Technology, working on the characterization of copolymers by NMR. I was also a Research Assistant in the Environmental Materials Laboratory of China Building Materials Academy, working on synthesis of FEVE coating. These research expe

21、riences have enriched my knowledge and experimental skills for polymer synthesis and enabled me to operate many facilities deftly, such as NMR, GPC, FTIR, vacuum glove box and rotary evaporator.In the summer of 2010, I was selected to attend the program “BUCT-Cambridge Summer School” in the Universi

22、ty of Cambridge. During the three weeks in the UK, I visited the Department of Chemical Engineering and Biotechnology and did experiments relevant to my research its labs. In Cambridge, I also did a case study about the biopharmaceutical market. This deepened my understanding of commercial prospects

23、 of drug delivery technologies, such as the demands of different patients for drug delivery systems and competitiveness of different health testing equipments. Besides the University of Cambridge, I also visited the University of Oxford, Imperial College London, University of Birmingham, and Univers

24、ity of Loughborough. I also established the contact with Dr Rongjun Chen who is the Group Leader of Biomaterials and Drug Delivery Group at the University of Leeds when I was in the UK, and have been communicating with him via emails since then, discussing about polymer synthesis and characterizatio

25、n and drug delivery research. I believe the above mentioned academic backgrounds and various relevant experiences have prepared myself well for the PhD study on polymer drug delivery research for the treatment of various diseases including cancers in Dr Rongjun Chens Lab at the University of Leeds.D

26、. Aim of overseas studyThe aim of my PhD study is to apply polymer nanotechnology to drug delivery in order to improve the safety and pharmaceutical efficacy of drugs that need precise intracellular delivery. I will design and synthesize biodegradable amino acid-based polymer vectors, which are effi

27、cient, safe, cost-effective and amenable to large-scale manufacturing. I will then evaluate the polymer-based targeted intracellular delivery of biological drug payloads （including siRNA, therapeutic peptide and antibody） against a well-validated intracellular drug target, such as Bcl-2, for cancer

28、treatment. The intention is to combine the highly novel chemistry expertise surrounding the delivery polymer with the biological expertise around the discovery and development of a variety of drug payloads. The novel polymer delivery technology to be developed will open the door to a wide variety of

29、 cytoplasmic and nuclear targets, previously thought to be inaccessible to biological therapy for various disease including cancers. In addition, I will investigate the fundamental mechanisms of the interaction between polymers/polymer-drug entities and different membrane models （artificial lipid me

30、mbranes, erythrocytes and more complex nucleated mammalian cells） and obtain a better understanding of the rules controlling the uptake of macromolecules into cells.E. Research methodsThe project would break down into discrete stages as described below:（1） Polymer synthesisAmino acid derivatives （e.

31、g. lysine derivative） will be used to carry out the N-Carboxyanhydride ring opening polymerization in order to obtain a polymer brush, which could be the backbone of target polymer. Then environmentally （e.g. pH and temperature） responsive groups will be grafted to the main chain by ATRP or Michael

32、Addition, etc. Fluorescent polymers would be prepared by coupling organic fluorophores （e.g. fluorescein isothiocyanate and Cy5） onto the polymers. Cleavable linker chemistry （e.g. disulfide bond） would be introduced onto the polymer backbone for drug conjugation. Polyethylene glycol would be added to the polymers to increase their biocompatibility and bioavailability. （2） Characterization of polymersThe structures, molecular weights and compositions of the synthesized peptide polymers will be characterized by NMR, mass spectrometry, GPC and HPLC etc. Th