海藻酸钠的疏水改性及释药性能研究

为了提高对疏水性药物的负载量和缓释作用,将海藻酸钠氧化后与十二胺反应使其进行疏水改性.对改性后聚合物结构进行了表征.研究了聚合物在水溶液及盐溶液中的粘度变化;将聚合物分散于NaCl/CaCl2的混合溶液中制备成凝胶微球,对药物布洛芬进行了包埋释放实验.结果表明,疏水改性后的海藻酸钠粘度增加,其凝胶微球对布洛芬负载量提高,具有较好的缓释作用.     

海藻酸钠水凝胶的制备及其在药物释放中的应用

近年来,由于智能水凝胶在药物的控制释放、基因传送、组织工程等领域的应用前景诱人,研究者对智能水凝胶的研究十分活跃。合成类水凝胶常用的单体有丙烯酸及其衍生物、丙烯酰胺及其衍生物等,合成水凝胶具有较好的稳定性,但其生物降解性和生物相容性较差。天然类水凝胶的原料主要有壳聚糖、海藻酸钠、纤维素、淀粉等。由于这些天然多糖具有较好的生物相容性和生物降解性,同时价廉易得,因此,天然类水凝胶在药物控制释放领域更具有优势。海藻酸钠是β-D-甘露糖醛酸(β-D-mannuronic,M)和α-L-古洛糖醛酸(α-L-guluronic,G)按照(1→4)糖苷键连接而成的线型聚合物,每个糖醛酸单元上含有一个羧基,因此,海藻酸钠在中性或碱性条件下呈现聚阴离子电解质的性质。本文综述了海藻酸钠水凝胶的制备方法,包括物理交联法、化学交联法、酶交联法、互穿聚合物网络等;概述了海藻酸钠水凝胶在药物释放中的应用,包括口服给药、皮下给药、黏膜给药、肺部给药、经皮给药等;最后讨论了海藻酸钠水凝胶在研究与应用中存在的问题。     

电荷密度和疏水性对疏水改性聚丙烯酰胺与牛血清蛋白相互作用的影响

对比研究了牛血清蛋白(BSA)与部分水解的未改性聚丙烯酰胺(PAM-AA)、疏水改性聚丙烯酰胺(PAM-C12)和含有丙烯酸基团的疏水改性聚丙烯酰胺(PAM-C12-AA)之间的相互作用.等温滴定量热实验结果表明,除PAM-C12外,其他聚合物与BSA的结合焓均为放热,随AA含量的增加,放热焓值增大.与PAM和PAM-C12相比,PAM-C12-AA能够诱导BSA二级结构和微环境的明显变化,表明疏水性和电荷密度均对聚合物与BSA相互作用有重要影响.另外,不同浓度的PAM-C12-AA与BSA的作用方式不同,当聚合物的浓度略高于临界胶束浓度(CMC)时,由于聚合物的量较少,BSA分子改变其构型从而最大程度地与聚合物结合;当聚合物的浓度远高于CMC时,更多的聚合物链结合到BSA分子的正电荷"patch"上,PAM-C12-AA与BSA的紧密聚集体利于BSA二级结构的稳定.     

疏水改性凝胶的合成及其药物释放性能的研究

以偶氮二异丁腈为引发剂,通过化学引发聚合合成甲基丙烯酸β-羟乙酯(HEMA)/N-乙烯基吡咯烷酮(NVP)二元共聚物和HEMA/NVP/甲基丙烯酸乙酯(或甲基丙烯酸丁酯)三元共聚物水凝胶,研究了凝胶在不同的酸度介质中对小分子药物阿司匹林的释放过程,结果表明,在模拟胃肠道条件下,随着疏水性单体的加入使凝胶的药物释放速率减缓,可实现药物的控制缓释作用。     

羧甲基壳聚糖水凝胶制备及其在药物控释中的应用

以戊二醛为交联剂制备了一系列羧甲基壳聚糖pH敏感水凝胶 .研究了合成条件对羧甲基壳聚糖水凝胶溶胀性能的影响 .实验结果表明羧甲基壳聚糖的脱乙酰度、交联剂用量对水凝胶溶胀率的影响较大 .pH=3 0时 ,水凝胶收缩 ,而pH =1 0 ,5 0 ,7 4 ,9 0时 ,水凝胶溶胀 ,且在碱性条件下水凝胶的溶胀率远大于酸性条件下的溶胀率 .包埋在此水凝胶中的水杨酸释放随载药介质的pH值和水凝胶半径大小的变化而显著不同 ,pH =1 0条件下载药的水凝胶的释药率大于pH =7 4 ,12 0条件下的释药率 ,且水凝胶的半径越大 ,释药速度和释药率也越大     

大茴香醛改性海藻酸钠凝胶的制备及释药性能

在酸催化下使海藻酸钠与对甲氧基苯甲醛(又名大茴香醛)发生缩醛化反应,使其疏水改性,并将其制备成凝胶。利用红外(FTIR)、荧光、透射电镜(TEM)、扫描电镜(SEM)、紫外、热重分析(TGA)对产物进行了表征。结果表明,大茴香醛成功地与海藻酸钠发生了反应。该凝胶可以作为药物载体对牛血清白蛋白进行包埋释放,结果发现,改性后的产物其载药率和缓释性能比未改性的海藻酸钠有了一定的提高。     

壳聚糖─海藻酸钠微囊对蛋白质控制释放的研究

采用乳化法制备了可注射用壳聚糖海藻酸钠微囊, 其粒径小于２００ μｍ ,且具有相对较窄的近似高斯分布。牛血清白蛋白作为模型药物在微囊中的包埋率可超过５０ ％ 。通过壳聚糖在海藻酸钠微囊表面的复合,牛血清白蛋白从微囊中的持续释放时间从几个小时延长到半个月以上。     

肽类药物口服剂型材料及控制释放性能研究Ⅰ.壳聚糖─海藻酸盐微囊对胰岛素的控释作用

应用壳聚糖-海藻酸盐微囊技术制备了一系列胰岛素微囊，并研究了不同反应条件如海藻酸钠浓度、壳聚糖浓度、壳聚糖分子量及壳聚糖溶液pH值对微囊的胰岛素包封率及其释放性能的影响。结果表明，海藻酸钠浓度越高，微囊对胰岛素的包封率越高，在模拟小肠液中释放速率越低；壳聚糖浓度越大，微囊的胰岛素包封率及其在模拟胃液中释放率越高，在模拟肠液中释放达最大值所需时间越长；而随壳聚糖分子量减小，微囊在胃液中释放率增高；壳聚糖溶液pH值的变化对微囊的胰岛素包封率未造成明显影响。     

栓塞型新型微包纳药物控释载体的制备及性能

为了抑制药物的突释效应, 减缓药物的释放速率, 实现不同药物的空间分配及顺序释放, 采用乳化法结合高压静电液滴法, 制备了内部包埋有几丁聚糖/海藻酸钙纳米囊的聚精氨酸/几丁聚糖/海藻酸盐微包纳体系(Nano-in-micro drug delivery system, NiM). 通过荧光标记的方法证实了“微包纳”结构并考察了NiM的理化性能. 以牛血清白蛋白及氟尿嘧啶作为药物模型, 考察了聚精氨酸/几丁聚糖/海藻酸盐微包纳体系对单一蛋白类药物和负载两种药物的缓释性能并进行了动力学模型拟合. 结果表明, Ritger-Peppas模型能够较好地模拟该溶胀控释系统的药物释放过程, 与实验结果比较吻合. 同时也证明了该新型载体体系具有无突释、释放速率减缓及顺序释放的功能, 为新型药物载体体系的研究提供了新的思路.     

Microencapsulation of DNA Within alginate microspheres and crosslinked chitosan membranes for in vivo application

Calf thymus DNA was microencapsulated within crosslinked chitosan membranes, or immobilized within chitosan-coated alginate microspheres. Microcapsules were prepared by interfacial polymerization of chitosan, and alginate microspheres formed by emulsification/ internal gelation. Diameters ranged from 20 to 500 Μm, depending on the formulation conditions. Encapsulated DNA was quantifiedin situ by direct spectrophotometry (260 nm) and ethidium bromide fluorimetry, and compared to DNA measurements on the fractions following disruption and dissolution of the microspheres. Approximately 84% of the DNA was released upon core dissolution and membrane disruption, with 12% membrane bound. The yield of encapsulation was 96%. Leakage of DNA from intact microspheres/capsules was not observed. DNA microcapsules and microspheres were recovered intact from rat feces following gavage and gastrointestinal transit. Higher recoveries (60%) and reduced shrinkage during transit were obtained with the alginate microspheres. DNA was recovered and purified from the microcapsules and microspheres by chromatography and differential precipitation with ethanol. This is the first report of microcapsules or microspheres containing biologically active material (DNA) being passed through the gastrointestinal tract, with the potential for substantial recovery.     

Pickering emulsions stabilized by hydrophobically modified alginate nanoparticles: Preparation and pH-responsive performance in vitro

pH-responsive Pickering emulsions were prepared, taking the hydrophobic modified calcium alginate nanoparticles (MCA) of pH sensitivity as emulsifiers. The MCAs were obtained via gelation between Ca²⁺ in emulsion and alginate sodium that reacted with diacetone acrylamide since alginate sodium was too hydrophilic to be used as a stabilizer. The effect of MCA characteristics, Ca²⁺ content, and pH on the preparation and property of emulsion was evaluated. Then, the released behaviors of MCA-stabilized emulsion loading oil-soluble drug of curcumin were investigated in vitro. The results demonstrated that Pickering emulsions released curcumin intestine-specifically (37% in 4 hours with a pH of 6.8), compared with the one in the gastric fluid (3% in 4 hours with a pH of 1.5), proving that MCA had similar pH sensitivity to alginates and probably as the promising candidate in oral drug controllable release.     

肌红蛋白在海藻酸钠水凝胶中的电化学和电催化特性

海藻酸钠(Sodium Alginate,SA)是由L-葡萄糖醛酸与D-甘露糖醛酸组成的高分子线性糖醛酸,常作为固定化酶包埋材料。本文研究了海藻酸钠水凝胶膜中的肌红蛋白在磷酸盐缓冲溶液中的直接电化学和酶催化性质,探讨了测定H2O2和NO2^-的可能性。     

Preparation and controlled degradation of oxidized sodium alginate hydrogel

Degradation is often a critical property of materials utilized in tissue engineering. Although alginate, a naturally derived polysaccharide, is an attractive material due to its biocompatibility and ability to form hydrogels, its slow and uncontrollable degradation can be an undesirable feature. In this study, the degradation behavior of hydrogel based on oxidized sodium alginate (OSA) crosslinked with Ca²⁺ was studied in phosphate buffer solution (PBS, pH = 7.4) and Tris-(hydroxymethyl) aminomethane–HCl (Tris–HCl, pH = 7.4) at 37 °C. The degradation behavior of OSA hydrogels with different degrees of oxidation was evaluated as a function of degradation time by monitoring the changes of molecular weight and weight loss. It was found that the degradation behavior relied heavily on the degree of oxidation and the surrounding medium. This result indicates that the degradation rates of OSA hydrogels can be controlled by changing the degree of oxidation.     

新疆褐煤疏水改性提高其成浆性能

针对新疆褐煤具有较高内水的问题,制备了阴离子AKD改性剂和非离子AKD改性剂,对褐煤颗粒进行疏水改性。研究了改性前后煤粒表面化学成分、孔隙分布、亲疏水性和Zeta电位等煤粒表面特性,并结合NSF分散剂在改性前后煤粒表面吸附量大小,探讨了改性前后褐煤水煤浆的成浆性、流变性和稳定性。结果表明,改性后煤粒孔隙结构降低,煤粒表面碳的相对含量增加,氧的相对含量降低,煤水界面接触角增加,煤粒疏水性能增强。NSF分散剂在改性煤表面吸附量增加,煤粒表面负电性增强。由阴离子AKD改性煤、非离子AKD改性煤制备的水煤浆最大成浆质量分数从原煤56.6%分别增加至61.0%、62.5%,浆体析水率从原煤13.97%分别降低至7.45%、7.89%,同时改性后煤粒制备的浆体均表现出剪切变稀的假塑性流体。因此,改性煤粒更容易制备高浓度、低黏度、高稳定性且易于储存和运输的水煤浆。     

Evaluation of the protection and release rate of bougainvillea (Bougainvillea spectabilis) extracts encapsulated in alginate beads

There is a growing demand in the food industry for natural food products to replace synthetic ingredients. Motivated by this fact, the present work studied the extraction of coloring compounds from Bougainvillea spectabilis under aqueous and ethanolic conditions, and the encapsulation of the extract in alginate beads. Ethanolic extraction was more efficient as reflected by the higher values for total phenols (6.78?±?0.24?mg EAG/g), betacyanins (5.04?±?0.13?mg/g), betaxanthines (1.35?±?0.06?mg/g,) and inhibition capacity (81.31?±?4.23%). FTIR analysis suggested the presence of interactions between the extract and the alginate chains. The release kinetics of compounds in alginate beads was measured under aqueous and ethanolic conditions at 25.0?°C and at 70.0?°C. Color was also monitored, showing that the color parameters followed a kinetics pattern similar to the released extract. However, the release of betalains exhibited a mixed behavior, reflecting interactions between the different compounds of the bougainvillea extract and the alginate chains. The extracts released from the beads were characterized to determine the preservation of their properties during encapsulation, concluding that the encapsulation is efficient to protect and release the bioactive compounds from bougainvillea extracts.     

海藻酸钠脱除重金属研究进展

重金属污染已成为全球性的环境问题,脱除重金属是治理重金属污染的主要途径。海藻酸钠(SA)本身无毒、性质稳定、价格低廉,具有较强的胶凝性、成膜性和络合能力,既可作为脱除重金属的吸附材料,又可作为脱除重金属的固定化载体,在重金属脱除中具有广泛的应用。本文重点综述了SA凝胶球、SA复合膜、SA纳米复合材料、SA分子印迹脱除重金属,以及SA作为单一固定化载体和复合固定化载体脱除重金属进展情况。展望了SA脱除重金属的应用前景。     

Preparation of antimicrobial sodium alginate with chito-oligosaccharide side chains

To provide sodium alginate (SA) with an antimicrobial property, we introduced chito-oligosaccharide (COS) via chemical bonding in a two-step procedure. We reacted COS with N-methylol acrylamide (NMA) with N-methylol groups to prepare acrylamidomethyl chito-oligosaccharide (COS–NMA). SA with COS side chains (SA–COS) was produced through a subsequent reaction of SA with COS–NMA. The chemical structure of SA–COS was confirmed by IR spectroscopy and ¹H NMR spectroscopy. With a two-step method, we successfully prevented insoluble-complex formation due to electrostatic attraction between chitosan and alginate. SA–COS showed excellent antimicrobial activity, with the growth of microorganisms completely suppressed by a small amount of COS (1.8 wt %). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1810–1816, 2001