聚酰胺-胺树状大分子的研究进展

聚酰胺-胺(PAMAM)是1985年由美国人Tomalia合成的一种树状大分子,现已广泛应用于基因载体、光电传感、废水处理、药物载体、催化剂等领域。本文综述了PAMAM树状大分子的结构和合成方法、细胞毒性,作为基因载体、药物载体所取得的成果以及PAMAM聚合物作为载体在胶质瘤治疗方面的研究进展及展望,并对今后胶质瘤放射治疗的研究方向进行了概述。     

核壳结构树状大分子的设计及其生物医学应用

核壳结构树状大分子(core-shell tecto dendrimers, CSTDs)是一类以相对高代树状大分子为核、相对低代树状大分子为壳的超结构树状大分子纳米体系。越来越多的研究表明,利用不同代的聚酰胺-胺[poly(amidoamine),PAMAM]树状大分子作为反应模块构建的CSTDs不仅具有比相对高代树状大分子更优异的理化性能,还克服了单代树状大分子在医学应用上的一些局限性(如有限的载药量和EPR效应等)。在此,本文综述了近年来CSTDs的几种制备方法,并分类介绍了基于CSTDs的纳米平台在生物学成像、化疗、基因治疗以及联合治疗等方面的应用。最后,结合CSTDs研究现状分析了其当前在生物医学领域中的挑战和机遇。     

PEG化PAMAM树状大分子的合成及其作为药物载体的研究

研究经聚乙二醇(PEG)进行表面修饰的聚酰胺-胺树枝状大分子作为药物载体时对药物的包裹及释放能力。用经三氟乙基磺酸单甲氧基(Tresylate)活化的相对分子质量为5000的单甲氧基聚乙二醇(Tresylated MPEG-5000)对聚酰胺-胺G4.0-PAMAM树状大分子修饰,目标产物PEG化树状大分子用FT-IR1、H NMR进行结构表征。MTT研究其细胞毒性。通过包裹与释放实验研究该药物载体对抗癌药物甲氨蝶呤(MTX)的包裹及释放能力。每个修饰后的树状大分子可包裹33个抗癌药物甲氨蝶呤分子,细胞毒指数较低,释药速度减慢。修饰后的树状大分子与未PEG化的树状大分子载体相比具有更强的包裹能力,并具有一定的药物缓释功能;细胞毒性试验表明,其胞毒性与未PEG化的树状大分子相比明显偏低。     

乙酰化可降低聚酰胺-胺的细胞毒性

背景：聚酰胺-胺型树枝状高分子纳米材料已被广泛应用于药物载体的研究,但由于整代聚酰胺-胺表面有大量带正电荷的氨基,具有一定的细胞毒性。 目的：观察乙酰化对聚酰胺-胺细胞毒性的影响。 方法：①细胞增殖检测：采用MTT法检测在含0,0.125,0.25,0.5,1,2,4 μmol/L乙酰化聚酰胺-胺的培养液中人胚肾293T细胞的增殖。②细胞形态：倒置荧光显微镜观察在含4 μmol/L乙酰化聚酰胺-胺的培养液中人胚肾293T细胞的形态。③细胞周期：流式细胞术检测在含0,5,10,15,20 mg/L乙酰化聚酰胺-胺的培养液中人胚肾293T细胞的细胞周期。 结果与结论：聚酰胺-胺对293T细胞具有一定的细胞毒性,在4 μmol/L浓度下48 h的细胞存活率仅为52%,而乙酰化可显著降低聚酰胺-胺的细胞毒性(P < 0.01); 聚酰胺-胺孵育的细胞发生团缩,伸展性变差,而乙酰化聚酰胺-胺孵育的293T细胞与正常培养细胞基本一致,具有良好的伸展性;乙酰化聚酰胺-胺对细胞周期无影响,而聚酰胺-胺在20 mg/L较高质量浓度时可使细胞S期产生阻滞。表明乙酰化可以降低聚酰胺-胺的细胞毒性。     

聚酰胺——胺的聚电解质复合物血液相容性研究

本文用六水哌嗪和甲撑双丙烯酰胺合成了聚酰胺-胺(PAA)，并由藻朊酸(AA)。羧甲基纤维素(CMC)和聚甲基丙烯酸(PMA)按不同比例与PAA形成六种聚电解质复合物(PEC)．同时采用动态凝血时间试验和抗人血小板膜糖蛋白Ⅲa单克隆抗体(SZ-21)放免试验综合评价了这六种PEC的血液相容性。其中由藻朊酸和聚酰胺-胺(2：1)形成的PEC具有优异的血液相容性。     

组氨酸修饰聚酰胺-胺型树状高分子提高血清中基因转染效率的研究

组氨酸的咪唑环由于其独特的质子化机理而受到了广泛的关注。研究表明,组氨酸修饰的基因载体可对抗血清对基因转染的影响,提高载体在血清中的基因转染效率。本研究利用氨解反应将组氨酸接枝到聚酰胺-胺树枝状高分子(PAMAM)的表面,制备了一种新型的PAMAM衍生物—组氨酸修饰的聚酰胺-胺树枝状高分子(His-PAMAMG4)。利用1HNMR对His-PAMAM G4进行表征,证明一个PAMAM G4分子上接枝37个组氨酸分子。对His-PAMAM G4/DNA复合物进行结合DNA能力、粒径、表面电位、粒子形态等理化性能的表征,证明该新型聚合物对DNA分子具有良好的压缩能力。细胞活性检测结果表明,His-PAMAM G4对Bel 7402和Hela细胞的毒性均显著低于未经修饰的PAMAM G4。His-PAMAM G4在血清中的转染效率与PAMAM G4相比大幅度提高,也显著高于阳离子聚合物PEI 25k和市售商品阳离子脂质体Lipofectamine。因此,His-PAMAM G4有望成为一种高效、安全、可在体内应用的非病毒基因载体。     

聚酰胺-胺型纳米载体在基因治疗中的研究进展

聚酰胺-胺型树枝状高聚物可与DNA形成纳米尺寸的聚电解质复合物,具有很高的稳定性和溶解性,因此被认为是较好的基因载体.现有研究对聚酰胺一胺型树枝状高聚物介导的基因入胞机制已经较为清楚,体外研究证实该载体基因转染效率高.转基因能长期、稳定表达,且细胞毒性小;体内研究则证实在尤文肉瘤防治、心脏移植、恶性疟疫苗和肺纤维化防治等诸多疾病的基因治疗领域有较好的前景.     

皮肤组织工程-细胞支架的构筑及其生物相容性评价

皮肤组织工程的发展提供了一种无损伤修复创伤和功能重建的皮肤治疗模式.作为组织工程的三要素之一,细胞支架发挥着重要的作用.为满足组织工程中对细胞支架在力学性能、物理结构及生物相容性等方面的要求,我们首先制备了聚乳酸(PDLLA)、聚乳酸-己内酯(PLACL)多孔支架,并以生物相容性较好的猪的无细胞真皮(acellular dermis matrix,ADM)为参比,分别把三种材料植入大鼠背部肌层,术后定期取大鼠皮下埋藏组织进行组织学检测.结果发现PDLLA与PLACL多孔支架的降解周期、力学性能、孔隙率及其孔径都可以根据皮肤组织工程中的要求进行调控.组织学检查,移植物内无明显炎性细胞,21天后,均完全血管化且分布较均匀.说明PDLLA与PLACL的生物相容性较ADM差,但并未出现明显的异物排斥反应,两者的生物相容性基本上可以满足组织工程中对支架的要求,这为聚乳酸类人工皮肤的进一步研究提供了有意义的实验依据.     

新型多肽聚酰胺-胺型靶向药物载体的载药性能及细胞吸收和毒性

背景：前期研究通过噬菌体展示体内筛选方法获得了一条NCI-H460非小细胞肺癌特异结合的多肽(Lung cancer targeting peptide, LCTP),将该多肽与修饰的聚酰胺-胺型(Polyamidoamine, PAMAM)树枝状高分子材料连接制备了纳米靶向药物载体PAMAM-Ac-FITC-LCTP,该载体在体内外对非小细胞肺癌NCI-H460具有很好的靶向性。 目的：在前期研究基础上,进一步研究PAMAM-Ac-FITC-LCTP靶向载体对阿霉素的包埋、释放及其细胞吸收和毒性性能。 方法：以筛选到的多肽LCTP为靶向剂,构建了PAMAM-Ac-FITC-LCTP靶向载体。采用物理包埋法将PAMAM-Ac- FITC-LCTP与阿霉素连接,通过体外透析实验观察载体对药物的缓释功能,共聚焦显微镜观察细胞对药物的吸收。以游离阿霉素作为对照,MTT法观察载体载药后对NCI-H460细胞的作用。 结果与结论：PAMAM-Ac-FITC-LCTP对阿霉素的最大包埋率为7.46%。载体对药物具有明显的缓释作用,离子浓度、pH和温度对药物的释放具有影响,说明PAMAM-Ac-FITC-LCTP主要是通过静电相互作用与阿霉素结合。PAMAM-Ac- FITC-LCTP/阿霉素短时间内较单独药物更高效进入NCI-H460细胞,而复合物24 h 的细胞毒性与阿霉素对细胞的毒性基本一致。以上结果说明PAMAM-Ac-FITC-LCTP可能是一个肿瘤治疗和诊断中很有用的药物靶向传输载体。     

壳聚糖-羧甲基壳聚糖复合膜的研制及其生物相容性评价

壳聚糖膜降解较慢^[1]，为了加快其降解速度，研制了壳聚糖-羧甲基壳聚糖复合膜(以下简称复合膜)并进行了生物学评价。结果表明，该复合膜具有很好的生物相容性，可以满足体内植入膜的基本要求。     

Side‐On Nematic Liquid Crystal Dendrimers Based on PAMAM and PPI as Dendritic Scaffolds: Synthesis and Characterization

The design, synthesis, and investigation of two series of side‐on dendrimers displaying nematic liquid crystal behavior at room temperature are described. The dendritic structures are derived from poly(amidoamine) (PAMAM‐(NH₂)_n) or poly(propylene imine) dendrimers (PPI‐(NH₂)_n) (with n = 4, 8, 16, 32, and 64) containing lateral attached mesogenic units in the periphery. The materials are characterized by ¹H, ¹³C nuclear magnetic resonance (NMR) spectroscopy, matrix‐assisted laser desorption/ionization‐mass (MALDI‐TOF MS) spectrometry, differential scanning calorimetry (DSC), polarized optical microscopy (POM), and x‐ray diffraction spectroscopy. All dendrimers exhibit nematic mesophase behavior at room temperature. Conoscopic studies reveal that the nematic phase is uniaxial. The relationship between the structure of the two dendrimer series and the mesomorphic behavior is discussed.

     

Enhanced transfection efficiency of low generation PAMAM dendrimer conjugated with the nuclear localization signal peptide derived from herpesviridae

Abstract

Polyamidoamine (PAMAM) dendrimer is an extensively studied polymer in the biomedical research because of its low polydispersity, distinct molecular structure, and surface functionalities. Generally, a high-generational PAMAM dendrimer is used for gene delivery because transfection efficiency is dependent on charge density; however, an increase in charge density induces disruption of the cellular membrane, and damage to the membrane results in cytotoxicity. In this study, we selected PAMAM generation 2 to reduce the cytotoxic effect and conjugated RRILH and RRLHL sequences, nuclear localization signals (NLS) derived from herpesviridae to PAMAM generation 2. The transfection efficiency of RRILH-PAMAM G2 and RRLHL-PAMAM G2 was similar to that of polyethylenimine (PEI) in Neuro2A, HT22, and HaCaT cells, whereas their transfection efficiency was much higher than that of PEI in NIH3T3 cells. RRILH-PAMAM G2 showed relatively lower cytotoxicity than did RRLHL-PAMAM G2 in all cell lines, but the transfection capacity of the two polymers was similar. Our study shows that low-generational PAMAM dendrimer conjugated with NLS sequences has potential as an alternative to PEI in gene delivery.     

Design and Synthesis of Phosphorescent Iridium Containing Dendrimers for Potential Applications in Organic Light‐Emitting Diodes

Three phosphorescent dendrimers ( IrC1 , IrC3 , and IrF2 ) with an iridium complex core and oligocarbazole or oligofluorene substituted ligands were synthesized and characterized. The structures of the oligocarbazole were designed to maintain high triplet energy of the ligands so that phosphorescence quenching in the resulting dendrimers can be prevented, while the oligofluorene in IrF2 resulted in undesired phosphorescence quenching. Best performance was obtained from an IrC3 based electrophosphorescent light‐emitting device with a maximum luminance of 13 060 cd · m^?2 at a driving voltage of 11.5 V and a peak current‐efficiency of 4.3 cd · A^?1 at a luminance of 3 400 cd · m^?2, owing to its high PL efficiency, and efficient energy transfer between the iridium complex core and the ligands.

     

Synthesis of Diphenylamine‐Substituted Phenylazomethine Dendrimers and the Performance of Organic Light‐Emitting Diodes

Summary: We have designed and synthesized novel diphenylamine‐substituted phenylazomethine dendrimers (DP‐Gn, n = 1, 2) as hole‐transport materials for organic light‐emitting diodes (OLEDs). These dendrimers similar to phenylazomethine dendrimers showed a stepwise metal complexation with metal ions. They have good multi‐redox properties attributed to the terminal amine moieties and excellent thermal stabilities. Double layer EL devices utilizing the dendrimers as a hole‐transport material and Alq₃ as the emitting and electron transport materials were fabricated. The EL performances of the devices increased with higher dendrimer generations. Moreover, by using the metal ion (0.5 equiv. SnCl₂)‐complexed DP‐G2 dendrimers, the luminance and EL efficiency of the devices were drastically increased by more than double and over 30%, respectively. These metal complexable phenylazomethine dendrimers are novel and promising materials for highly efficient OLEDs.

Structure of the diphenylamine‐substituted phenylazomethine dendrimer DP‐G2.     

Synthesis of a heparinized poly(organophosphazene)

The synthesis of a new potential anti-thrombogenic polymer is described. Limited halogenation of an aryloxysubstituted polyphosphazene, followed by quaternization with triethylamine yielded a polymer capable of forming polyelectrolyte complexes with sodium heparin. The results of preliminary clotting tests with bovine blood are presented.     

Synthesis of Ionic Dendrimers and Their Potential Use as Electrolytes for Lithium–Sulfur Batteries

A series of ionic dendrimers is synthesized and used as conducting salt in carbonate‐based electrolytes for Li/S‐cells. The resulting electrolytes display increasing viscosity with increasing chain length of the side chains, both in the first‐ and second‐generation dendrimers. Higher conductivity is observed for the first‐generation dendrimers as compared to the second‐generation ones. While all cells show high cycle stability, the differences in dendrimer structure also influence the electrochemical behavior of the Li–S cells. Thus, discharge capacities of the corresponding Li–S cells correlate both with the viscosity and the conductivity of the electrolytes. The best electrolyte system is obtained with a first‐generation dendrimer having a short side chain, D1‐1, having the lowest viscosity and the highest conductivity, which delivers discharge capacities of 1150 mAh g_sulfur^?1 @ 0.5 C and 780 mAh g_sulfur^?1 @ 1 C.     

聚乳酸－乙醇酸共聚物合成与降解

本文对聚乳酸-乙醇酸(PLGA)的合成制备的多种方法进行了阐述,对聚乳酸-乙醇酸(PLGA)的降解性能和降解机理进行了概述.     

Biocompatibility and degradation of poly(ether-ester) microspheres: in vitro and in vivo evaluation

Microspheres of a hydrophobic and a hydrophilic poly(ether–ester) copolymer were evaluated for their in vitro and in vivo biocompatibility and degradation. The microspheres prior to and after sterilization were tested for in vitro cytotoxicity. The in vivo biocompatibility of the poly(ethylene glycol) terephthalate and poly(butylene terephthalate) (PEGT/PBT) microspheres was evaluated subcutaneously and intramuscularly for 24 weeks in rabbits. The in vivo degradation of the microspheres was studied microscopically and compared to the in vitro degradation. The in vitro and in vivo studies showed the biocompatibility of the microspheres of both the hydrophobic and the hydrophilic PEGT/PBT copolymer. Extracts of these microspheres showed no cytotoxic reactivity in the in vitro cytotoxicity test. Sterilization of the microspheres by gamma irradiation did not affect the cytotoxicity. PEGT/PBT microspheres injected subcutaneously and intramuscularly in rabbits showed a mild tissue response in vivo, in terms of the inflammatory response, the foreign body reaction and the granulation tissue response. Although an in vitro degradation experiment showed a decrease in molecular weight due to hydrolysis, the in vivo degradation of the microspheres was slower than previously published.     

Cell-mediated immunity to cytomegalovirus (CMV) and herpes simplex virus (HSV) antigens in the acquired immune deficiency syndrome: Interleukin-1 and interleukin-2 modifyin vitro responses

Peripheral blood lymphocytes (PBL) were obtained from five patients with the acquired immune deficiency syndrome (AIDS), six homosexual males with lymphadenopathy, and five normal heterosexual controls. Modulation of virus-specific immunity was assayedin vitro by measuring the lymphocyte blastogenic response and the production of lymphokine (leukocyte inhibition factor; LIF) by PBL stimulated with herpes simplex virus (HSV) or cytomegalovirus (CMV) antigens in the presence or absence of interleukin-1 (IL-1) and interleukin-2 (IL-2). PBL from the control and lymphadenopathy subjects responded to both antigens in the lymphocyte transformation assay (LT) measured on day 7, and the responses were significantly enhanced in cultures grown in the presence of antigen and IL-2 (1 U/ml). PBL from the AIDS patients were unresponsive, but responsiveness was restored by the addition of IL-2. The addition of IL-1 (0.02 µg/ml) to antigen-stimulated PBL cultures failed to enhance the proliferative responses in all three study groups. LIF production was assayed in the supernatants from day 1 PBL cultures. LIF was not produced by PBL from AIDS patients grown in the presence of viral antigens, whereas three of five patients from the lymphadenopathy group, and three of five control subjects gave rise to positive responses. The addition of IL-1 to the antigenstimulated cultures enhanced LIF production in the control and lymphadenopathy groups but not in the AIDS patients. The addition of IL-2 did not modulate LIF production by antigen-stimulated PBL from the control oR AIDS patients while suppressing the LIF response of the similarly stimulated PBL from the lymphadenopathy patients.     

Synthesis,Characterization and Biocompatibility of Novel Biodegradable Cross-linked Co-polymers Based on Poly(propylene oxide) Diglycidylether and Polyethylenimine

Novel biodegradable cross-linked co-polymers were prepared from poly(propylene glycol) diglycidylether (PPGDGE) and poly(ethylene imine) (PEI). PPGDGE and PEI were mixed at ambient temperature with varying PEI concentrations of 10, 15, 18.5, 25, 30, 40 and 50 wt%; the homogenous PPGDGE/PEI mixtures obtained were cured at elevated temperatures, resulting in formation of PPG–PEI cross-linked co-polymers via ring-opening reaction of PPGDGE with PEI. The physicochemical and biological properties of these co-polymers were dependent on the PEI content and the extent of curing reaction. The glass transition temperature of PPG–PEI cross-linked co-polymers varied in the range from ?14 to +42°C, while the co-polymers displayed composition-dependent mechanical behavior, from brittle to ductile with increasing PEI content from 18.5 wt% to 40 wt%. Chinese hamster ovary (CHO) cells were cultured on the PPG–PEI co-polymers; the MTT assay was used to measure cell viability and determine the cytotoxicity. The cell viability rate, relative to tissue-culture polystyrene (TCPS), increased from 49% to 125% with increasing PEI content from 18.5 wt% to 40 wt%. Although epoxy monomers usually exhibit cytotoxicity, the epoxy groups were exhausted via curing reaction in the fully cross-linked co-polymers. The PEI-cured PPG epoxy resin, i.e., PPG–PEI cross-linked co-polymers obtained in this study, showed excellent biocompatibility.