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1、河南工程學(xué)院《專業(yè)英語》考查課 專業(yè)論文 高分子材料的研究進(jìn)展 學(xué)生姓名： 學(xué) 院： 機(jī)械工程學(xué)院 專業(yè)班級： 材控1242 專業(yè)課程： 專業(yè)英語 任課教師： 2015年11月20日 Abstract : This paper contains an ester bond and an amide bond and an ester bond and an

2、amide bond hybrid bond polymer biomaterials synthesis, modification and biocompatibility of research results. Rich in hydrophilic groups degradable and degradation products can be absorbed by organisms or metabolic polymer material can meet the needs of tissue engineering , uncoupling protein -conta

3、ining molecules, drug molecule active group polymer biomaterials will have a more large potential applications. Key words : polymer biomaterials ; polyester ; polyamide 1 Introduction Biological material known as biomedical materials, refers to an organism for treatment, diagnosis and replacement

4、 tissues and organs corrupted or promotional material of their functions. It is divided into metal materials, polymer materials, ceramics and composites four kinds [1]. The late 1980s, people of biotechnology to the study of biological materials, combined with biological elements and functions to bu

5、ild the desired biologically active material, which made the concept of tissue engineering. Tissue engineering marks the medicine will be out of the scope of the organization of organ transplantation, tissues and organs into the manufacturing era, thus tissue engineering in the 21st century high-tec

6、h industry has great potential. Polymer science of the 20th century a strong impetus to the booming development of biological materials, bio-polymer material carrying drugs and release of biological scaffold material has broad application prospects. Currently, the medical polymer materials around th

7、e world has more than 90 varieties, more than 1800 kinds of products, according to the Western countries consumption growth rate of 10% to 20% annually. Tissue engineering polymer desired biologically active materials not only have good biocompatibility, but also biodegradable, and easily absorbed o

8、r metabolic degradation products, and in favor of cell adhesion, growth, proliferation and gene expression and regulation, etc. An ester bond and an amide bond is readily hydrolyzable bond, and therefore the polymer is a polymer containing multiple biomaterials ester bond or an amide bond. Polyglyco

9、lic acid and its copolymers hydroxy acids, such as polylactic acid (PLA) and glycolic acid and lactic acid copolymer (PLGA) is typical of biological material containing ester bonds, poly amino acids are typical amide bond-containing biological material. Their synthesis, modification and application

10、in the biomedical aspects of a more extensive research. 2 polyester-based biomaterials Poly lactic acid and glycolic acid and lactic acid copolymer is generally used glycolide or lactide in the organic tin catalyst obtained by cationic polymerization mechanism, they can degrade in the physiologica

11、l environment, the degradation The product can be metabolized and eliminated from the body. Since 1970 polyglycolic acid has become commercially available surgical sutures [2,3], with glycolic acid and lactic acid monomer biodegradable polymer caused widespread concern, the researchers biodegradable

12、 degradation mechanisms depending on the desired mechanical properties and design the polymer [4]. PLA and polyglycolic acid (PGA) polymers are highly crystalline, by hydrolysis in the physiological environment of the first occurrence in the amorphous regions, since there are side-methyl-PLA, PGA ex

13、hibited stronger than the hydrophobic, and therefore of PLA hydrolysis difficult than hydrolysis of the PGA. The copolymerization of glycolic acid with lactic acid, by adjusting the ratio of the two monomers, is expected to give the desired rate of hydrolysis of biological material [5]. PLA, PGA and

14、 PLGA has good biocompatibility and safety, and their carrying of biological scaffolds have been widely studied [6] on drugs. Drug carrying particle micro-encapsulated nano particles, and, generally spray drying method, three methods of W / O / W double emulsion solvent evaporation method and

15、aerosol extraction method [7]. Drug-loaded particles can enter the organism by the oral, subcutaneous and intramuscular way. Akiko Japanese scientists, who reported to the PLA and PLGA microencapsulation of material for luteinizing hormone release in vitro studies, the results showed that, pH value

16、of the medium, salt concentration and other factors will affect the release of the drug. Hongkee et al [9] reported a mixture of PLA and PGA micro encapsulating material to control bovine serum albumin, transfer and pancreatic protein ferritin analog protein release, we found that the microencapsula

17、tion can achieve a continuous release of an antigen, can effectively replace the multiple injections of antigens, have potential applications in terms of vaccine inoculation. Zambaux et al reported the preparation and characterization of load protein C (a plasma factor) of PLA nanoparticles in 1999,

18、 and found that protein C is adsorbed on the hydrophobic interaction based on PLA nanoparticles. Prabba, who reported carrying different sizes of PLGA nanoparticles on DNA in 2002, the result is the smaller the particle size, the higher the efficiency of DNAs carrying. Breitenbach et analysis of lin

19、ear polyesters carrying proteins and other macromolecules hydrophilic macromolecules on the basis of unfavorable factors, by changing the polyester structure and increase the hydrophilic polymer, effectively regulate the degradation rate of the polymer and the release rate of the drug. They were syn

20、thesized with polyethylene oxide (PEO) branched star structure polyester and dextrin or polyvinyl alcohol-based chain, polyester comb polymer branched, research shows that they can be used as intestinal ideal drug carrier material outside. Vila, who designed and fabricated with polyethylene glycol (

21、PEG) for the coating of PLA nanoparticles coated with chitosan and chitosan nanoparticles PLGA nanoparticles carrying on their research activity of the protein The results showed that the stability of hydrophilized engineered nanoparticles and proteins contained negative amount are greatly increased

22、. Sahli, who studied the PLA and PEO-PLA nanoparticles in mice with the after effects of plasma factor found no hydrophilic structure of PLA nanoparticles clumping factor is very sensitive, PEO-PLA nanoparticles containing hydrophilic structure of cohesion factors have a stronger role in the resista

23、nce, it can be a long time stability in the blood. Biocompatibility studies with PLGA as A segment to the B segment of PEO ABA block copolymer Zange and others with fibroblast cell culture model, found that increasing the content of PEO, the degradation rate of the copolymer is increased, as fiber c

24、ell adhesion and growth thereon situation is more favorable. In PLA or PLGA-based materials, through enhanced modified, it can be made to obtain the required scaffold for tissue engineering. Wang et al. Reported a hydroxyapatite ceramic particles to enhance PLA, the material can be given biological

25、 activity, can induce the formation of bone tissue hydroxyapatite similar on the surface. Campbell found that a mixture of the polycaprolactone, PLGA and hydroxyapatite have potential applications in bone tissue engineering. The porous component composition of a mixture of these may be degraded in w

26、ater and serum-containing medium, and the degradation rate of materials increases with PLGA content quickly. Although the PLA, PLGA or PGA have a good biocompatibility been widely studied and used as part of the clinical application of the drug carrying material and other material aspects of the im

27、plant, but as a long-term implanted device materials, their acidic degradation productsIt is also of concern, because the acidic degradation products of cell adhesion and growth, unfavorable, and may lead to tissue inflammation. To overcome these problems, and others with diethanolamine LU Zejian of

28、 PLA modified by introducing hydrophilic amine has a weak alkaline, to neutralize the acidic degradation products, the surface of the material to improve cell adhesion, promotes cell increase. Ambrosio et al. In polyphosphazene mixture and poly hydroxy acids are biological materials degrade system i

29、nvestigated by pH change, and found degradation products polyphosphazenes and poly hydroxy acids can neutralize acidic degradation products, reduce the degradation of the mixture acidic, increasing the biocompatibility of the material. Therefore, PLA, PGA and PLGA-based biomaterials, if trying to i

30、ntroduce a hydrophilic portion, will be more conducive to carrying and releasing drugs. If introduced to neutralize acidic degradation products of components, will impart better biocompatible materials. GA and LA ratio changes, you can adjust the degradation rate of PLGA. Polyester with side carbox

31、yl or amine groups have good solubility in water, and loading and sustained-release pharmaceutical. Cammas, who first aspartic acid as the starting material synthesis of macromolecular drugs may carry a high molecular weight poly (β- malic acid). Kazuhiro others with 3 (s) - [(benzyloxy carboxy) met

32、hyl] -1,4-dioxane-2,5-dione ring-opening polymerization to obtain a carboxyl group-containing side polyglycolic acid. Fietier et al. The serine amino protection, and then into the lactone ring, and then the lactone ring-opening polymerization and deprotection, synthesis of amine functional polyester

33、 with a side. But, so far about the band rarely seen side of carboxyl or amine polyester reports biomedical area. 3 poly-amino acids are typical of biological material polylactic acid amide-containing polymers they are rich in the side functional groups, and the degradation products are simple α-

34、amino acids, biological materials to do with it, has obvious advantages. Early polyglutamic acid synthesis, an amino acid is first reacted with an excess of phosgene N- carboxy anhydride (NCA), and then the anionic ring-opening polymerization. Phosgene synthesis NCA, requires a large excess of highl

35、y toxic phosgene, is not conducive to the stoichiometry and master balance. 1988 Daly reported the synthesis of NCA with triphosgene work, as triphosgene is a crystalline solid, store safe and easy to use, stoichiometry, soluble in organic solvents such as THF and hexane, which greatly facilitates t

36、he synthesis of the NCA. However, in addition to poly-glutamic acid, other poly amino acid is difficult to dissolve, and poor physical properties and processing properties. Recently, however, Klok through continuous open loop - deprotection step polymerization of highly branched dendritic water-solu

37、ble poly-lysine, such polymers is expected to have wide use in biological medicine. Therefore, it has not yet developed a poly-amino acid products have value. Over the past decade, in order to improve the solubility of poly-amino acids and workability, studied copolymerization very active. Cammas a

38、nd others with one end of the primary amino groups of PEO initiated β- benzyl ester -N- -L- aspartic acid anhydride-containing hydrophilic segments PEO and di-block copolymer poly amino acid ester segments, the copolymer in water to form stable micelles, and freeze-dried to obtain a powder having a

39、diameter of 35nm micelles. Kataoka reported the use of a primary amine group at one end of polyethylene glycol (PEG) initiator substituted lysine NCA, obtained diblock polymers, and of partially substituted for lysine structural adhesive bundle of influence. Yuan et al., With both ends of polyoxyeth

40、ylene primary amine initiators L- phenylalanine NCA, to obtain a better hydrophilic triblock polymers. Kang et al., Both ends of a primary amine of polypropylene oxide (PPO) triggered NCA β- benzyl glutamate to give the middle PPO triblock polymer, the polymer and blood compatibility gas permeation

41、studies have shown that the introduction of amorphous poly amino acids PPO, help to improve the permeability and gas anticoagulant effect of block copolymers. Since poly (γ- -L- glutamic acid methyl ester) with a natural look and feel like leather, but its resilience and good adhesion to cells. Uch

42、ida et al. Reported separately with a primary amine, tertiary amine and hydrazine as initiator, synthetic polymer containing polyurethane segment and poly (γ- benzyl glutamate) segments, studies have shown that the polymer modified resilience and adhesion of cells have been improved significantly.

43、4-hydroxy acids and amino acid copolymers type of biological material Hydroxy acids and amino acid copolymers formed, will combine excellent performance of two types of polymers are biodegradable, absorption and metabolism of the very potential of tissue engineering materials. Since glycolide or la

44、ctide open-loop via a cationic mechanism, NCA via anionic ring opening mechanism, and therefore can not be put together lactide and copolymerizing NCA. Barrera, who first synthesized cyclic dimer containing lysine units and amino acid structural unit to be protected, then the cyclic dimer lactide co

45、 together via cationic ring-opening polymerization, go protection , you get containing 2.6% of lactic acid lysine unit and lysine copolymer. Amine groups of the copolymer can be conjugated peptides, giving it a better biological activity. Jin, who synthesized serine-containing 2% lactic acid and ser

46、ine, copolymers of the free hydroxyl groups at both ends of the PEO isocyanato reaction, increasing the amorphous content of the polymer, improved polymer Biofacies capacitive. So far, the amino acid modification is introduced into the main structure and hydrophilic adjust its crystallinity, the

47、reby improving the polymers biodegradation behavior and histocompatibility. Although researchers have realized a total of polymerization of amino acids and hydroxy acids, but amino acid content of the copolymer of structural units is very low. Related amino acid copolymers reported in terms of biolo

48、gical material is very rare. Reference: [1] 俞耀庭(YUYao-ting),陳興棟(CHENXin-dong).生 物醫(yī)用材料(Biomaterials).天津大學(xué)出版社(TianjinUniversityPress),第1版(Edition1),2000:12. [2] GilgingDK,ReedAM.Polymer,1979,20:1459. [3] ReedAM,GildingDK.Polymer,1981,22:494. [4] LisaB.InternationalJournalofPharmaceutics,1995, 116

49、(1):1. [5]KissE,Vargha-ButlerEI.ColloidsandSurfaceB: Biointerfaces,1999,15(3～4):181. [6] AkikoK,ShgeruK,AkiraS,etal.J.Controlled Rel.,1996,40(3):269. [7] ClaudiaW,EricD.J.ControlledRel.,1998,51(2～ 3):327. [8] RocioH,MiguelRF.AdvancedDrugDelevery Reviews,2001,52(1):5. [9] HongkeeS,RobintonT

50、,ChienY.J.ControlledRel., 1995,35(2～3):137. 中文原文: 摘要:綜述了含酯鍵和酰胺鍵以及酯鍵和酰胺鍵混合鍵的高分子生物材料的合成、改性以及生物相容性等方面的研究成果。富含親水基團(tuán)的可降解以及降解產(chǎn)物可被生物體吸收或代謝的高分子材料可滿足組織工程的需要,含可偶聯(lián)蛋白分子、藥物分子活性基團(tuán)的高分子生物材料將有更大的應(yīng)用潛力。 關(guān)鍵詞:高分子生物材料;聚酯;聚酰胺 1 引言 生物材料又稱生物醫(yī)用材料,是指對生物體進(jìn)行治療、診斷和置換壞損的組織器官或增進(jìn)其功

51、能的材料。它分為金屬材料、高分子材料、陶瓷材料及復(fù)合材料四種[1] 。20世紀(jì)80年代后期,人們將生物技術(shù)應(yīng)用于生物材料的研究,結(jié)合生物要素和功能去構(gòu)建希望的有生物活性的材料,從而提出了組織工程的概念。組織工程標(biāo)志著醫(yī)學(xué)將走出組織器官移植的范疇,進(jìn)入制造組織和器官的時代,因而組織工程是21世紀(jì)具有巨大潛力的高科技產(chǎn)業(yè)。20世紀(jì)的高分子科學(xué)的蓬勃發(fā)展有力地推動了生物材料的發(fā)展,生物高分子材料在藥物載送釋放和生物支架材料等方面有廣泛的應(yīng)用前景。目前,全世界的醫(yī)用高分子材料已有90余個品種,1800多種產(chǎn)品,西方國家的消耗按每年10%～20%的速度增長。組織工程期望的高分子生物活性材料不僅有良好的生

52、物相容性,而且可生物降解和降解產(chǎn)物容易吸收或代謝,并且有利于細(xì)胞的粘附、生長、增殖以及基因表達(dá)和調(diào)控等。 酯鍵和酰胺鍵是容易水解的化學(xué)鍵,因此高分子生物材料多是以含酯鍵或酰胺鍵的聚合物。聚羥基酸及其羥基酸的共聚物,如聚乳酸(PLA)和羥基乙酸和乳酸的共聚物(PLGA)是典型的含酯鍵的生物材料,聚氨基酸是典型的含酰胺鍵的生物材料。對它們的合成、改性以及在生物醫(yī)用方面的應(yīng)用有較廣泛的研究。 2 聚酯類生物材料 聚乳酸和羥基乙酸與乳酸的共聚物一般是用乙交酯或丙交酯在有機(jī)錫催化劑作用下按陽離子機(jī)理聚合得到的,它們可以在生理環(huán)境中降解,其降解產(chǎn)物可被代謝而排除體外。自1970年聚羥基乙酸成為商用外科縫

53、合線以來[2,3],以羥基乙酸和乳酸為單體的生物降解聚合物引起廣泛關(guān)注,研究者根據(jù)所期望的降解機(jī)制及力學(xué)性能設(shè)計可生物降解的聚合物[4]。PLA和聚羥基乙酸(PGA)都是高結(jié)晶的聚合物,它們在生理環(huán)境中的水解首先發(fā)生在非晶區(qū),由于PLA有側(cè)甲基,表現(xiàn)出比PGA更強(qiáng)的憎水性,因此PLA的水解比PGA的水解困難。將羥基乙酸與乳酸共聚合,通過調(diào)節(jié)兩單體的配比,可望得到預(yù)期水解速率的生物材料[5] 。PLA、PGA及PLGA有良好的生物相容性和生物安全性,它們在藥物載送和生物支架材料方面已得到廣泛研究 [6] 藥物載送的微包囊、微粒及納米粒子的制備,一般有噴射干燥法、W/O/W雙乳液溶劑蒸發(fā)

54、法和氣溶膠提取法等三種方法[7]。負(fù)載藥物的粒子可以通過口服、皮下注射和肌肉注射等方式進(jìn)入生物體。日本科學(xué)家Akiko等人報道了以PLA和PLGA為材料的微包囊對促黃體激素的體外釋放研究,結(jié)果表明,介質(zhì)的pH值、鹽濃度等因素都會影響藥物的釋放。Hongkee等人[9] 報道了PLA和PGA混合物為材料的微包囊對牛血清蛋白、轉(zhuǎn)移鐵蛋白及胰蛋白等模擬蛋白的控制釋放,發(fā)現(xiàn)這種微包囊可以實現(xiàn)對抗原的連續(xù)釋放,可以有效代替抗原的多次注射,在疫苗的接種方面有潛在的應(yīng)用。Zambaux等人于1999年報道了負(fù)載蛋白C(一種血漿因子)的PLA納米粒子的制備及表征,并發(fā)現(xiàn)蛋白C基于疏水作用吸附在PLA納米粒子上

55、。Prabba等人在2002年報道了 不同粒徑的PLGA納米粒子對DNA的載送,結(jié)果是粒徑愈小對DNA的載送效率越高。Breitenbach等在分析線形聚酯對蛋白類大分子及其它親水大分子的載送的不利因素的基礎(chǔ)上,通過改變聚酯結(jié)構(gòu)和增加聚合物的親水性,有效調(diào)節(jié)聚合物的降解速率和藥物的釋放速率。他們合成了以聚氧化乙烯(PEO)為支鏈的星形結(jié)構(gòu)聚酯和以糊精或聚乙烯醇為主鏈、聚酯為支鏈的梳形結(jié)構(gòu)聚合物,研究表明,它們可作為腸外藥物的理想載送材料。Vila等人設(shè)計并制備了以聚乙二醇(PEG)為涂層的PLA納米粒子、以殼聚糖為涂層的PLGA納米粒子和殼聚糖納米粒子,研究了它們對活性蛋白的載送,結(jié)果表明,經(jīng)

56、親水化改造的納米粒子的穩(wěn)定性和對蛋白的載負(fù)量都大大增加。Sahli等人 研究了PLA和PEO-PLA納米粒子在小鼠體內(nèi)與血漿因子的作用后發(fā)現(xiàn),無親水結(jié)構(gòu)的PLA納米粒子對凝聚因子很敏感,含親水結(jié)構(gòu)的PEO-PLA納米粒子對凝聚因子有較強(qiáng)的抵抗作用,能在血液中較長時間穩(wěn)定。Zange等人用成纖細(xì)胞培養(yǎng)模式研究了以PLGA為A段,以PEO為B段的ABA型嵌段共聚物的體外生物相容性,發(fā)現(xiàn)增加PEO的含量,共聚物的降解速率增加,成纖細(xì)胞在其上面的粘附和增長情況更加良好。 以PLA或PLGA為基礎(chǔ)材料,通過增強(qiáng)改性,可以制得組織工程所需的支架材料。Wang等人報道了以羥基磷灰石生物陶瓷粒子增強(qiáng)

57、PLA,可賦予材料的生物活性,能在其表面上誘導(dǎo)形成類似骨組織的羥基磷灰石。Campbell等人發(fā)現(xiàn)由聚己內(nèi)酯、PLGA及羥基磷灰石組成的混合物在骨組織工程中有潛在應(yīng)用價值。由這些成分組成的多孔混合物可以在水和含血清的介質(zhì)中降解,并且材料的降解速率隨PLGA含量的增加而加快。 雖然PLA、PLGA或PGA等有良好的生物相容性,在用做藥物載送材料和其它植入材料方面得到廣泛研究和部分臨床應(yīng)用,但作為長期植入的器件材料,它們降解產(chǎn)物的酸性也備受關(guān)注,因為偏酸性的降解產(chǎn)物對細(xì)胞的粘附和增長不利,并且可能導(dǎo)致組織發(fā)炎。為克服這些問題,盧澤儉等人用二乙醇胺對PLA改性,通過引入有弱堿性的親水胺基,

58、來中和降解的酸性產(chǎn)物,改進(jìn)細(xì)胞在該材料表面的粘附性,促進(jìn)細(xì)胞的增長。Ambrosio等人以聚磷腈和聚羥基酸的混合物為生物材料,通過考察降解體系的pH變化,發(fā)現(xiàn)聚磷腈的降解產(chǎn)物可以中和聚羥基酸的酸性降解產(chǎn)物,降低混合物降解的酸性,增加材料的生物適應(yīng)性。 因此,以PLA、PGA和PLGA為基礎(chǔ)的生物材料,若設(shè)法引入親水部分,將更有利于藥物的載送和釋放。若引入可中和酸性降解產(chǎn)物的組分,將更好地賦予材料的生物適應(yīng)性。改變GA和LA的配比,可以調(diào)節(jié)PLGA的降解速率。 帶側(cè)羧基或胺基的聚酯有良好的水溶性,并可負(fù)載和持續(xù)釋放藥物。Cammas等人第一次以天冬氨酸為起始原料合成出可載送大分子藥物

59、的高分子量的聚(β-蘋果酸)。Kazuhiro等人用3(s)-[(芐氧基羧基)甲基]-1,4-二氧六環(huán)-2,5-二酮開環(huán)聚合,得到含側(cè)羧基的聚羥基酸。Fietier等通過對絲氨酸胺基的保護(hù),然后環(huán)化成內(nèi)酯,再對內(nèi)酯開環(huán)聚合及去保護(hù),合成出有側(cè)胺基的功能聚酯。不過,至今很少見到有關(guān)帶側(cè)羧基或胺基的聚酯在生物醫(yī)用方面的報道。 3 聚氨基酸類生物材料 聚氨基酸是典型的含酰胺鍵的聚合物,它們富含側(cè)功能基,且降解產(chǎn)物是簡單的α-氨基酸,用它做生物材料,具有明顯的優(yōu)越性。聚谷氨酸的早期合成方法,都是先用氨基酸與過量光氣反應(yīng)生成N-羧酸酐(NCA),然后再陰離子開環(huán)聚合。用光氣合成NCA,需要大大過量的劇

60、毒光氣,不利于化學(xué)計量和掌握平衡。1988年Daly等報道了用三光氣合成NCA的工作,由于三光氣是晶狀固體,儲存安全和使用方便,可化學(xué)計量,能溶于THF和己烷等有機(jī)溶劑,大大方便了NCA的合成。不過,除聚谷氨酸外,其它聚氨基酸很難溶解,且物理性能及加工性能較差。不過,最近Klok經(jīng)過連續(xù)開環(huán)-去保護(hù)步驟聚合得到高度支化的樹枝狀水溶性聚賴氨酸,預(yù)期該類聚合物在生物醫(yī)藥方面有廣泛用途。因此仍未就聚氨基酸開發(fā)出有應(yīng)用價值的產(chǎn)品。 近十多年來,為了提高聚氨基酸的溶解性和加工性,對其共聚改性的研究十分活躍。Cammas等人用一端為伯胺基的PEO引發(fā)β-芐基-L-天冬氨酸酯-N-羧酸酐,得到含親水鏈段P

61、EO和聚氨基酸酯鏈段的二嵌段共聚物,該共聚物在水中能形成穩(wěn)定的膠束,并經(jīng)過冷凍干燥得到直徑為35nm的膠束粉末。Kataoka等人報道了用一端為伯胺基的聚乙二醇(PEG)引發(fā)取代賴氨酸的NCA,得到了二嵌段聚合物,并研究了部分取代的賴氨酸結(jié)構(gòu)對膠束化的影響。Yuan等人用兩端都為伯胺基 的聚氧化乙烯引發(fā)L-苯基丙氨酸的NCA,得到有較好親水性的三嵌段聚合物。Kang等人用兩端為伯胺基的聚氧化丙烯(PPO)引發(fā)β-芐基谷氨酸酯的NCA,得到中間為PPO的三嵌段聚合物,對該聚合物的血液相容性和氣體滲透性研究表明,在聚氨基酸中引入無定型的PPO,有利于提高嵌段共聚物的抗血凝作用和氣體的滲透性。 由

62、于聚(γ-甲基-L-谷氨酸酯)的外觀和手感與天然皮相似,但它的回彈性和對細(xì)胞的粘附性不好。Uchida等人報道了分別用伯胺、叔胺和肼為引發(fā)劑,合成含聚氨酯鏈段和聚(γ-芐基谷氨酸酯)鏈段的聚合物,研究表明,改性后的聚合物的回彈性及對細(xì)胞的粘附性都得到顯著提高。 4 羥基酸和氨基酸共聚物類生物材料 羥基酸和氨基酸形成的共聚物,將綜合兩類聚合物的優(yōu)良性能,是生物可降解、吸收和代謝的十分有應(yīng)用潛力的組織工程材料。由于乙交酯或丙交酯的開環(huán)是經(jīng)由陽離子機(jī)理,NCA開環(huán)是經(jīng)由陰離子機(jī)理的,因此不能將交酯和NCA置于一起共聚合。Barrera等人先合成出含有乳酸結(jié)構(gòu)單元和胺基被保護(hù)的賴氨酸單元的環(huán)狀二聚體

63、,然后將該環(huán)狀二聚體與丙交酯一起經(jīng)由陽離子開環(huán)共聚合,再去保護(hù),就得到含賴氨酸單元2.6%的乳酸和賴氨酸的共聚物。該共聚物的胺基可偶聯(lián)短肽,賦予它更好的生物活性。Jin等人合成了含絲氨酸2%的乳酸與絲氨酸的共聚物,共聚物中的自由羥基與兩端是異氰酸根的PEO反應(yīng),增加了聚合物的無定形成分,改進(jìn)了聚合物的生物相容性。 至今,氨基酸的改性主要是引入親水結(jié)構(gòu)和調(diào)整其結(jié)晶性,進(jìn)而改善聚合物的生物降解行為和組織相容性。盡管有研究者實現(xiàn)了氨基酸與羥基酸的共聚合,但共聚物中氨基酸結(jié)構(gòu)單元的含量很低。有關(guān)氨基酸的共聚物在生物材料方面的研究報道十分罕見。 參考文獻(xiàn)： [1] 俞耀庭(YUYao-ting),

64、陳興棟(CHENXin-dong).生 物醫(yī)用材料(Biomaterials).天津大學(xué)出版社(TianjinUniversityPress),第1版(Edition1),2000:12. [2] GilgingDK,ReedAM.Polymer,1979,20:1459. [3] ReedAM,GildingDK.Polymer,1981,22:494. [4] LisaB.InternationalJournalofPharmaceutics,1995, 116(1):1. [5]KissE,Vargha-ButlerEI.ColloidsandSurfaceB: Biointe

65、rfaces,1999,15(3～4):181. [6] AkikoK,ShgeruK,AkiraS,etal.J.Controlled Rel.,1996,40(3):269. [7] ClaudiaW,EricD.J.ControlledRel.,1998,51(2～ 3):327. [8] RocioH,MiguelRF.AdvancedDrugDelevery Reviews,2001,52(1):5. [9] HongkeeS,RobintonT,ChienY.J.ControlledRel., 1995,35(2～3):137.

66、 評 定 項 目 分 值 成 績 1、選題：科學(xué)實用，有新穎性，屬于材料科學(xué)與工程范疇具體而不空泛。 10 2、論點(diǎn)：論文論點(diǎn)正確，觀點(diǎn)鮮明，主題突出。 20 3、論文結(jié)構(gòu)：論文結(jié)構(gòu)合理，層次清晰，邏輯性強(qiáng)。 20 4、論證：獨(dú)立思考問題并完成論文，能夠理論聯(lián)系實際，論文內(nèi)容充實，論證嚴(yán)密，引用的數(shù)據(jù)或資料詳實可靠。 30 5、創(chuàng)新：有新意。 10 6、寫作規(guī)范：符合學(xué)術(shù)論文的基本體例，語言通順，篇幅適當(dāng)，格式規(guī)范。 10 總成績： 教師： 時間：