水溶性O-羟乙基壳聚糖的合成

壳聚糖[β-1→4）-2-氨基-2脱氧-D-葡萄糖]是目前发现的生物界唯一存在的碱性氨基多糖,具有无毒、可生物降解、良好的成膜性和生物相容性,近年来已在水处理、医药、食品、化妆品、农业等领域显示了其独特的应用用价值。但壳聚糖只溶于酸,在很大程度上限制了它的推广应用。通过降解     

表面截留聚乳酸的壳聚糖纤维的制备及其与聚乳酸的相容性

为了提高壳聚糖纤维和聚乳酸的相容性,采用表面截留法用消旋聚乳酸(PDLLA)对壳聚糖(CS)纤维表面进行修饰。在此基础上,利用模压成型法制备了修饰前后的CS纤维与左旋聚乳酸(PLLA)复合材料,并对CS纤维和基体PLLA之间的相容性进行了分析。研究结果表明:CS纤维表面成功截留了PDLLA分子,截留法修饰的CS纤维表面形态保持较为完好。与基体PLLA的界面黏结性和相容性得到了提高,修饰后的CS纤维明显提高了复合材料的抗弯性能。     

羧乙基壳聚糖的合成及表征

壳聚糖是甲壳素的N-脱乙酰基产物,并具有良好的螯合重金属离子、纺丝性和成膜性,且无毒副作用,广泛应用污水处理、食品、生物医用材料等领域[1-3].水溶性壳聚糖的合成及应用近年来文献报道很多[4-8].但对于水溶性羧乙基壳聚糖的合成报道较少.     

羟乙基淀粉的羟乙基取代位置的研究

将羟乙基淀粉进行甲基化-水解-还原乙酰化反应，产生羟乙基葡萄糖的部分甲基化糖醇乙酸酯衍生物，应用气相色谱/化学电离质谱（GC/CIMS）和气相色谱/电子轰击质谱/质谱（GC/EIMS/MS）联用技术研究了羟乙基在淀粉糖环上的取代位置，发现G-2位取代的量是总取代量的82.0％。     

酸性离子液体催化合成N-氰乙基-N-羟乙基苯胺

N-氰乙基-N-羟乙基苯胺是一种具有广泛用途的染料中间体,针对传统合成方法中的缺陷,以1-丁基-3-甲基咪唑硫酸氢盐([BMIM]HSO 4)为催化剂,丙烯腈和N-羟乙基苯胺为原料,建立了N-氰乙基-N-羟乙基苯胺的绿色合成新工艺。系统考察了离子液体种类、离子液体用量、底物比例等因素的影响规律,结果表明,[BMIM]HSO 4用量为0.8 mmol,n(N-羟乙基苯胺)∶[KG-*3/5]n(丙烯腈)=1∶[KG-*3/5]1.2,反应温度为90℃,反应时间为12 h时,N-氰乙基-N-羟乙基苯胺产率最高(89%),离子液体循环使用5次后,催化活性基本保持不变。     

聚乳酸/肝素缓释微囊复合材料组织相容性研究

研究了三种不同包覆材料的肝素微胶囊／聚乳酸(PLA)复合材料的组织相容性。结果表明，随着胶囊中壳聚糖浓度的增大，肝素的释放速率变慢。皮肤刺激、皮内刺激、热原、全身急性毒性和细胞培养等试验表明，制备的复合材料在生物学评价试验中均呈阴性反应，材料无明显毒性，材料中不存在潜在致敏性物质，所含热原含量符合生物体的要求。由此表明，肝素缓释微胶囊／PLA复合材料符合三维多孔材料的要求，且具有优良的组织相容性。     

脱氢枞氧基聚氧乙烯缩水甘油醚接枝羟乙基壳聚糖水凝胶制备及其性能

通过脱氢枞醇聚氧乙烯（10）醚（DA（EO）₁₀H）与环氧氯丙烷缩合后,再在NaOH存在下脱氯化氢得到脱氢枞氧基聚氧乙烯（10）缩水甘油醚（DA（EO）₁₀GE）,然后通过DA（EO）₁₀GE对羟乙基壳聚糖（HECTS）的接枝制备DA（EO）₁₀GE接枝羟乙基壳聚糖（DA（EO）₁₀GE-g-HECTS）,最后利用Genipin对DA（EO）₁₀GE-g-HECTS进行交联,得到DA（EO）₁₀GE-g-HECTS/Genipin水凝胶。研究结果表明：DA（EO）₁₀GE对HECTS糖单元摩尔比的增加能提高DA（EO）₁₀GE-g-HECTS的接枝度,并延长其与Genipin交联形成凝胶的时间;增加Genipin的用量可提高接枝产物与Genipin交联形成凝胶的能力;负载于DA（EO）₁₀GE-g-HECTS/Genipin凝胶中的氯霉素在人工肠液中的累积释放率与时间的关系,可以很好地用Boltzmann函数描述,且提高接枝度和降低Genipin用量有利于提高药物的最终累积释放率;低接枝度DA（EO）₁₀GE-g-HECTS经Genipin交联形成的载药凝胶,其药物释放行为符合一级动力学方程的特征。     

化学修饰壳聚糖的血液相容性

壳聚糖是无毒、可生物降解、具有生物相容性的天然碱性多糖。本文综述了近年来提高壳聚糖的血液相容性的方法及以壳聚糖为原料制备肝素替代品的研究。壳聚糖分子上接枝血液相容性高分子、引入亲水基团或负电基团、酰化改性等均能提高壳聚糖的血液相容性;以壳聚糖为原料制备肝素的替代品可通过在壳聚糖分子上引入磺酸基,或将壳聚糖氧化成6-羧基壳聚糖后再引入磺酸基来实现。对今后如何进一步提高壳聚糖衍生物的血液相容性研究前景进行了展望。     

新的液晶性壳聚糖衍生物——氰乙基壳聚糖的合成与表征

甲壳素是自然界蕴藏量最丰富的天然高分子化合物之一,但人们对它的了解却远不如纤维素和淀粉.仅就液晶领域而言,纤维素衍生物的液晶性早已为人们所认识,例如氰乙基纤维素的液晶性已有很多研究.     

功能化聚乳酸微球改性聚乳酸膜片表面及其细胞相容性

以两亲三嵌段共聚物PEO PPO PEO及其氨基酸、多肽RGD衍生物作为微球制备过程中的表面稳定剂 ,低分子量的聚乳酸作为成核材料 ,采用o w乳液溶剂挥发法制备得到表面含不同氨基酸的聚乳酸微球 ,荧光标记手段证明了氨基酸存在于微球的表面 ;利用溶胀嵌入固定法将微球固定到具有生物惰性聚乳酸膜片表面 ,制备得到了具有良好稳定性的微球改性聚乳酸生物惰性膜片 ;成骨细胞相容性测试表明 ,氨基酸尤其是多肽RGD在生物惰性聚乳酸表面的引入能较大程度地提高聚乳酸生物惰性表面的细胞相容性 ,能较好地诱导细胞行为如细胞粘附、增殖等过程的发生 ,为实现对细胞行为的诱导控制提供了一种新途径 .     

微波辅助壳聚糖接枝聚乳酸共聚物的合成及表征

在微波辅助下,以辛酸亚锡为催化剂、壳聚糖(CS)为大分子引发剂引发消旋丙交酯（D,L-LA）本体开环聚合制备了壳聚糖接枝聚乳酸共聚物。通过正交实验研究了微波功率、催化剂用量、反应温度和反应时间对聚合反应的影响,确定了最佳合成条件。并通过红外光谱、元素分析、核磁共振氢谱、X-射线衍射和热分析对接枝共聚物的结构与性能进行了表征。结果表明,在微波条件下,能快速、有效地合成预定结构的壳聚糖接枝聚乳酸共聚物;聚乳酸支链的引入,有效削弱了壳聚糖分子间和分子内较强的氢键作用,与相应的壳聚糖比较,共聚物的结晶性能下降,热分解温度降低;原料配比对共聚物的结构与性能有显著影响,随nD,L-LA/nCS糖环数值增大,共聚物中平均乳酰单元数逐渐增大,共聚物的结晶性能、起始分解温度逐渐下降。     

Antibacterial poly(D,L-lactide) (PDLLA) fibrous membranes modified with quaternary ammonium moieties

<正>Antibacterial poly(D,L-lactide)(PDLLA) fibrous membranes were developed via electrospinning,followed by surface modification which involved plasma pretreatment,UV-induced graft copolymerization of 4-vinylpyridine(4VP) and quaternization of the grafted pyridine groups with hexylbromide.The success of modification with quatemized pyridinium groups on the PDLLA fibrous membranes was ascertained by X-ray photoelectron spectroscopy(XPS).The antibacterial activities of these membranes were assessed against Gram-positive Staphylococcus aureus(S.aureus) and Gram-negative Escherichia coli(E.coli).The PDLLA fibrous membranes modified with quaternized pyridinium groups showed antibacterial efficiency against both bacteria as high as 99.999%.The results demonstrated that the antibacterial activity was based on the interaction of the positive charge of pyridinium group and negatively charged cell membrane of bacteria, resulting in loss of membrane permeability and cell leakage.     

Synthesis and characterization of biodegradable block copolymers of ϵ-caprolactone and D,L-lactide initiated by potassium poly(ethylene glycol)ate

Poly(D ,L -lactide)–poly(ϵ-caprolactone)–poly(ethylene glycol)–poly(ϵ-caprolactone)–poly(D ,L -lactide) block copolymer (PLA–PCL–PEG–PCL–PLA) was prepared by copolymerization of ϵ-caprolactone (ϵ-CL) and D ,L -lactide (D ,L -LA) initiated by potassium poly(ethylene glycol)ate in THF at 25°C. The copolymers with different composition were synthesized by adjusting the mole ratio of reaction mixture. The resulted copolymers were characterized by ¹H-NMR, ¹³C-NMR, IR, DSC, and GPC. Efforts to prepare copolymers with the corresponding structure of PCL–PLA–PEG–PLA–PCL and D ,L -lactide/ϵ-caprolactone random copolymers were not successful. © 1997 John Wiley & Sons, Inc.     

Hydrolyzable poly(ester-urethane) networks from L-lysine diisocyanate and D,L-lactide/ϵ-caprolactone homo- and copolyester triols

Bioabsorbable poly(ester-urethane) networks were synthesized from ethyl 2,6-diisocyanatohexanoate (L -lysine diisocyanate) (LDI) and a series of polyester triols. LDI was synthesized by refluxing L-lysine monohydrochloride with ethanol to form the ester, which was subsequently refluxed with 1,1,1,3,3,3-hexamethyldisilazane to yield a silazane-protected intermediate. This product was then phosgenated using triphosgene. Polyester triols were synthesized from D,L-lactide, ?-caprolactone, or comonomer mixtures thereof, using glycerol as initiator and stannous octoate as catalyst. Polyurethane networks were cured using [NCO]/[OH] = 1.05 and stannous octoate (0.05 wt %) for 24 h at room temperature and pressure and 24 h at 50°C and 0.1 mm Hg. LDI-based polyurethane networks were totally amorphous and possessed very low sol contents. Networks based on poly (D,L-lactide) triols were rigid (T_g ∽ 60°C) with ultimate tensile strengths of ～ 40–70 MPa, tensile moduli of ～ 1.2–2.0 GPa, and ultimate elongations of ～ 4–10%. Networks based on ?-caprolactone triols were low-modulus elastomers with tensile strengths and moduli of ～ 1–4 MPa and ～ 3–6 GPa, respectively, and ultimate elongations of ～ 50–300%. Networks based on copolymers displayed physical properties consistent with monomer composition and were tougher than the networks based on the homopolymers. Tensile strengths for the copolymers were ～ 3–25 MPa with ultimate elongations up to 600%. Hydrolytic degradation under simulated physiological conditions showed that D ,L -lactide homopolymer networks were the most resistant to degradation, undergoing virtually no change in mass or physical properties for 60 days. ?-Caprolactone-based networks were resistant to degradation for 40 days, and high-lactide copolymer-based networks suffered substantial losses in physical properties after only 3 days. © 1994 John Wiley & Sons, Inc.     

Structure and compatibility of poly(vinyl alcohol)-silk fibroin (PVA/SA) blend films

The structure and compatibility of poly(vinyl alcohol)-silk fibroin (PVA/SF) blend films were analyzed by differential scanning calorimetry (DSC), thermomechanical (TMA) and thermogravimetric (TGA) analysis, x-ray diffractometry, and scanning (SEM) and transmission (TEM) electron microscopy. DSC curves of PVA/SF blend films showed a major endothermic peak at 220°C, along with a peak at 280°C. These endotherms were assigned to the thermal decomposition of the ordered PVA elements and to the thermal degradation of silk fibroin, respectively. The PVA/SF blends behaved in a manner intermediate to the pure components, as suggested by both contraction expansion and sample weight retention properties recorded by TMA and TGA measurements. The IR absorption spectra of the blends were identified as purely a composite of the absorption bands characteristic of both PVA and SF pure polymers. The X-ray diffraction patterns of PVA/SF blends showed overlapping spacing due to PVA and SF. A dispersed phase formed by spherical particles of 3–7 μm diameter was observed by SEM and TEM. All these findings suggest that PVA and SF are incompatible. © 1994 John Wiley & Sons, Inc.     

Enzymatic hydrolysis of poly(D, L-lactide) spread monolayers by cutinase

 The enzymatic hydrolysis of a model poly(D,L-lactide) by cutinase was studied by using a barostat surface balance. A theoretical approach based on the adaptation of the Michaelis–Menten scheme at the interface and a process of random fragmentation of the macromolecules was developed. The role of the interfacial organisation of the reaction products was discussed. Hydrolysis rate constant values and the specific activity were estimated and compared with those obtained for the hydrolysis of lipid monolayers. The process of fragmentation of the interfacial polymer structures was visualised by using AFM imaging. Received: 19 August 1996 Accepted: 13 December 1996     

Mechanical and thermal properties of polypeptide modified hydroxyapatite/poly(L-lactide) nanocomposites

A new type of polypeptide(poly(-benzyl-L-glutamate)(PBLG))modified hydroxyapatite(HA)/poly(L-lactide)(PLLA)nanocomposites(PBLG-g-HA/PLLA)were prepared by the solvent-mixing method,and their mechanical and thermal properties were investigated.The tensile test showed that the mechanical properties of PBLG-g-HA/PLLA nanocomposites were better than that of PLLA,even a 0.3 wt%content of PBLG-g-HA in the nanocomposites could make the tensile strength 12%higher than that of the neat PLLA sample,and the tensile mod...     

Helix formation by poly{bis(hydroxyethyl)-L-glutamine}

Circular dichroism spectra are reported for poly {bis(hydroxyethyl)-L-glutamine}. Its conformation is predominantly that of a statistical coil at or above ambient temperature in water. It becomes partially helical upon cooling. The helix-forming potential of this polypeptide in water is between that of poly(hydroxyethyl-L-glutamine) and poly(hydroxypropyl-L-glutamine). The polypeptide has a large helix content when the solvent is rich in trifluoroethanol.     

PLGA-(PEG-ASP)n共聚物的合成与性能研究

以辛酸亚锡[Sn(Oct)2]为催化剂,聚乙二醇／L-天冬氨酸预聚物[(PEG-ASP)n]为共引发剂,引发D,L—LA和GA开环共聚合成具有功能侧氨基的PLGA-(PEGASP)n共聚物。通过FTIR、^1H—NMR、DSC、表面接触角测定和细胞培养等方法研究共聚物的结构与性能。结果表明,共聚物为典型的非晶态聚合物;共聚物的亲水性以及对骨髓基质细胞的粘附能力和粘附效率均明显优于PLGA。     

Preparation and Characterization of Poly(D,L-Lactide) (PLA) and Poly(D,L-Lactide)-Poly(Ethylene Glycol) (PLA-PEG) Nanocapsules Containing Antitumoral Agent Methotrexate

Summary: The aims of the present work were to prepare and characterize nanocapsules containing antitumoral agent methotrexate (MTX) from poly(D ,L -lactide) (PLA) and poly(D ,L -lactide)-poly(ethylene glycol) diblock copolymer (PLA-PEG) with the purpose of administrating this drug by topical ocular route for primary ocular lymphoma treatment. Nanocapsules were prepared by the interfacial deposition of preformed polymer. The influences of the initial amount of MTX on the encapsulation efficiency, drug recovery and drug content, as well as the physicochemical properties of the particles were evaluated. The particle mean diameters were 246 and 146 nm, and zeta potential values were −38.8 and −33.6 mV, for the MTX-loaded nanocapsules prepared from PLA and PLA-PEG, respectively. The methotrexate content in the particles increased with the increasing in the drug amount added to the formulations, but the drug recovery decreased significantly. After 4 h of in vitro release, 28 and 86% of MTX was released from PLA and PLA-PEG nanocapsules, respectively.