微波辐射法氧化制备低分子量壳聚糖的实验研究

应用微波辐射技术氧化制备低分子量的壳聚糖，对影响壳聚糖分子量的工艺因素，如过氧化氢溶液浓度、反应时间、壳聚糖与过氧化氢溶液的固液比、微波功率等分别进行了实验研究。结果表明：在温度为70℃～80℃的条件下，用5％的H2O2，壳聚糖质量为8克时，可将高分子量的壳聚糖氧化成产率较高的低分子量壳聚糖。     

影响聚维酮碘溶液稳定性的因素及对策

目的探讨影响聚维酮碘溶液稳定性的因素及对策。方法对不同温度、酸度和储存方式条件下的聚维酮碘溶液的稳定性进行分析,讨论最佳的保存条件。结果储存方式、温度和酸度的变化都对聚维酮碘溶液的稳定性产生影响。棕色瓶见光开口贮藏和白色瓶见光开口贮藏在相同温度和湿度条件下对于碘的稳定性的保存效果较差,而棕色瓶密闭避光贮藏的效果最好。而同一包装方式下25℃贮藏较30℃为好,同一时间点相比较,25℃下贮藏时片剂质量及有效碘含量下降均较30℃下慢（P〈0.05）。当聚维酮碘溶液pH〉8时,储存性能不稳定,聚维酮碘溶液pH〈5.0时稳定性比较接近。结论聚维酮碘溶液采用棕色瓶密闭避光在25℃、pH〈5.0是的贮藏效果较好。     

影响聚维酮碘溶液稳定性的因素及对策

目的 探讨影响聚维酮碘溶液稳定性的因素及对策.方法 对不同温度、酸度和储存方式条件下的聚维酮碘溶液的稳定性进行分析,讨论最佳的保存条件.结果 储存方式、温度和酸度的变化都对聚维酮碘溶液的稳定性产生影响.棕色瓶见光开口贮藏和白色瓶见光开口贮藏在相同温度和湿度条件下对于碘的稳定性的保存效果较差,而棕色瓶密闭避光贮藏的效果最好.而同一包装方式下25 ℃贮藏较30℃为好,同一时间点相比较,25 ℃下贮藏时片剂质量及有效碘含量下降均较30℃下慢(P＜0.05).当聚维酮碘溶液pH＞8时,储存性能不稳定,聚维酮碘溶液pH＜5.0时稳定性比较接近.结论 聚维酮碘溶液采用棕色瓶密闭避光在25 ℃、pH＜5.0是的贮藏效果较好.     

壳聚糖导管材料的制备及力学性能研究

目的壳聚糖在组织工程血管支架、神经修复导管等方面虽有潜在的广泛用途,但体内降解慢,本实验研究壳聚糖导管在满足基本力学性能要求下尽量降低管壁的厚度,以缩短降解时间。方法在初始溶液中加入聚乙二醇、甘油,通过浸渍-沥滤法制备壳聚糖管状材料,研究不同的成型工艺参数对壳聚糖导管力学性能的影响。结果在初始溶液中加入适量的甘油有利于提高壳聚糖导管的断裂应力和断裂伸长率,但其杨氏模量无显著变化;2%的壳聚糖初始溶液较2.5%所制备的导管的断裂应力、断裂应变和杨氏模量高;制备过程浸入-干燥的次数为2次的较3次制备出的导管的断裂应力、断裂应变和杨氏模量高。结论初始溶液中甘油、壳聚糖浓度以及重复次数都会影响导管的力学性能,优化成型工艺能在满足基本力学性能要求下降低管壁的厚度以达到最佳效果。     

胶原/生物活性玻璃/壳聚糖增强型复合支架

背景：生物活性玻璃/胶原复合材料具有优良的成骨活性和的生物学性能,然而其在人体环境中易降解而导致支架溃散、力学性能下降。 目的：构建具有良好力学性能、抗降解性能和骨修复特性的胶原/生物活性玻璃/壳聚糖增强型复合支架。 方法：以壳聚糖作为分散剂,将生物活性玻璃粉体预先在壳聚糖溶液中均匀分散,然后与胶原溶液混合,结合冷冻干燥法制备多孔胶原/生物活性玻璃/壳聚糖增强型复合骨修复支架。采用傅里叶变换红外光谱仪、场发射扫描电子显微镜、X射线衍射仪、动态生物力学试验机等对复合支架的结构和性能进行表征。 结果与结论：由于壳聚糖和生物活性玻璃粉体在微酸性环境下的电荷吸引,使在壳聚糖中预分散的生物活性玻璃颗粒在复合支架中分散更均匀;壳聚糖的引入大量增加了机体中的羟基和氨基,使分子间的相互作用增强,显著提高了材料的抗压模量和强度;壳聚糖和胶原在分子尺度的混合,使胶原分子被壳聚糖包裹,降低了胶原酶对胶原分子的酶切能力,显著提高了复合支架的抗胶原酶解性;壳聚糖分子使生物活性玻璃颗粒更均匀的包裹在大分子基相中,减少了生物活性玻璃颗粒的团聚和暴露,导致复合支架在模拟体液中的矿化活性略微降低。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

蛋清热变过程中的光学特性变化

目的为解决手术中激光切割能力下降的问题,以鸡蛋蛋清为样本,研究热变过程中生物组织的光学特性变化。方法使用积分球系统测量650nm激光照射下的样本在热风枪加热下,从26％升温到99℃过程中的准直透射光、漫透射光和反射光光强随温度变化的数据,计算吸收系数和散射系数变化曲线。结果样本热变前光学特性受温度影响较小,热变过程中透射率降低,吸收系数和散射系数增大。结论手术中低强度激光照射组织发生热变使吸收能力下降,应保持较高激光强度以达到消融阈值。     

羧甲基壳聚糖作为植入可降解缓释微球辅料的实验研究

羧甲基壳聚糖作为一种高分子材料 ,具有良好的组织相容性和生物可降解性。本实验试图利用羧甲基壳聚糖作为植入环丙沙星微球的缓释辅料 ,并探索这一剂型的制备工艺、结构形态和体外释药特性。首先我们采用乳化交联技术制备微球 ;然后用扫描电子显微镜、红外光谱、及示差热分析等方法研究微球的结构和形态 ;建立体外持续流动释放系统初步检测微球的体外释放特性。实验结果发现 :微球的结构和形态受制备工艺条件如温度、离子强度、搅拌速度等因素的影响 ;一定工艺条件下制备的环丙沙星微球的体外释放时间可达 7d以上 ,释放行为符合 Higuchi方程。因此 ,我们认为 :羧甲基壳聚糖可作为环丙沙星可降解植入微球的缓释辅料 ;乳化交联技术是制备这一微球的有效方法 ,工艺简单、稳定     

硫酸长春新碱缓释药膜的制备及稳定性初步研究

目的制备出载硫酸长春新碱微球的胶原-壳聚糖缓释药膜,并考察该制剂的稳定性。方法采用W/O/O溶剂挥发法制备载硫酸长春新碱的聚乳酸/聚羟基乙酸共聚物(PLGA)微球,后把微球与壳聚糖、胶原溶液共混及二次冻干,制备出载硫酸长春新碱微球的胶原-壳聚糖药膜。对微球和药膜表面形态进行了电镜观察,测定了微球和药膜的包封率、载药量及药物释放,药物含量采用高效液相法检测。此外,还初步考察了缓释药膜的稳定性。结果制备的微球包封率达到79.0%±1.0%,微球药物的突释为27.2%±1.2%,制备成药膜后降低到18.0%±1.1%,采用该工艺流程制备出来的缓释药膜,药物突释明显减少。稳定性实验显示,该药膜在40℃条件下放置3个月药物含量下降到97.9%±0.1%,而高湿度或光照环境下放置10 d药物含量下降到91.4%±0.3%和91.2%±0.4%。结论药物包囊制成微球后与胶原、壳聚糖共混制备出的缓释药膜具有较好的释放特性和稳定性,有望成为一种实用的新型缓释抗肿瘤制剂。     

壳聚糖对幽门螺杆菌外膜屏障功能的影响

研究壳聚糖 (即脱乙酰壳聚糖 ,Chi tosan)对Hp外膜屏障功能的影响 ,以探讨壳聚糖抗Hp的作用机制 ,以 6种抑菌作用较好的壳聚糖溶液 ,3种 70 %脱乙酰、3种 88.5 %脱乙酰为试验材料。将Hp标准菌株SydneyStrain 1(SS1)、NCTC116 39、NCTC116 37加入上述壳聚糖溶液中 ,细菌浓度为 10 8CFU ml,将每种壳聚糖分别与Hp菌液加入 2 4孔加样板中 ,每孔 2ml,每种溶液做 5孔 ,在 37℃和微需氧条件下 ,12 0r min振荡 ,4 8h后取出孔内液 ,30 0 0r min离心 10min后 ,取上清液分别测葡萄糖含量、天门冬氨酸氨基转移酶 (AST)和γ 谷氨酰转肽酶(GGT)…     

羧甲基壳聚糖-羧甲基纤维素防粘连膜的制备及其理化特性

背景:壳聚糖能有效预防粘连,可制成不同的剂型,如凝胶、溶液、海绵状以及薄膜等,但其缺点是溶液、凝胶易流动,不易在局部形成较高浓度,而单纯应用壳聚糖制成海绵状及薄膜机械强度及韧性不够。目的:以羧甲基壳聚糖、羧甲基纤维素为主要成分,制备具有优良物理、生物性能,预防粘连的生物膜。方法:将羧甲基壳聚糖和羧甲基纤维素按一定比例混合,加入戊二醛、硫酸铝铵进行双交联,甘油增塑。根据膜的色泽、拉伸强度、吸水率、溶胀比等指标通过正交试验筛选处方构成,优化膜的制备工艺,初步确定膜的制备工艺流程。通过扫描电镜、红外光谱等对制备样本的理化特性进行检测,并将膜植入SD大鼠体内观察膜的降解情况。结果与结论:得到优化后膜的处方构成为:羧甲基壳聚糖/羧甲基纤维素为1:1;硫酸铝铵浓度为0.15%;甘油含量为0.8%;戊二醛含量为0.003%。在以上工艺条件下制得的膜呈半透明状,微黄,上表面略粗躁,下表面光滑;膜的平均厚度为0.09mm;吸水率为964%;溶胀比为3.25;干态下膜的最大拉伸强度为20MPa,湿态下膜的最大拉伸强度为5MPa;接触角平均为35°。羧甲基壳聚糖和羧甲基纤维素间形成了较强的分子间作用力。膜表面结构呈相互交错的纤维状,表面有不规则的孔状结构。膜植入鼠体内后10d左右水化成凝胶,1个月后体内完全降解吸收。提示羧甲基壳聚糖-羧甲基纤维素膜是一种生物相容性良好、可降解吸收、具有一定手术缝合强度的生物膜。     

Determination of rutin in human plasma by high-performance liquid chromatography utilizing solid-phase extraction and ultraviolet detection

The degradation kinetics of aplidine were investigated using reversed-phase high-performance liquid chromatography combined with UV detection. Aplidine consists of at least two isomers that undergo interconversion at a low rate. Influences of pH, temperature, buffer ions and ionic strength on the degradation kinetics were studied. The log kobs) -pH profile can be divided into three parts, a proton, a solvent and a hydroxyl-catalysed section. The stability-indicating properties of the used analysis technique as well as the identities of the main degradation products were checked using gradient liquid chromatography and mass spectrometric detection. The overall degradation rate constant as a function of the temperature under acidic and alkaline conditions obeys the Arrhenius equation. No catalytic influences were observed with phosphate and carbonate buffers and, in addition, the ionic strength showed no substantial effect on the stability, as expected. Results from gradient LC-MS indicated that hydrolysis of the ester groups present in the ring structure was the main degradation route. There is no difference in degradation rate constants for the individual isomers.     

Hydrophilic and cationic latex particles for the specific extraction of nucleic acids

The adsorption of BSA and RNA onto hydrophilic and thermosensitive poly(N-isopropyl-acrylamide) (NIPAM) latex particles was described as a function of pH, ionic strength and temperature. The hydrogel poly(NIPAM) latex was synthesized by precipitation polymerization in the presence of a cationic amino-containing monomer. The latex obtained was characterized in terms of particle size, and electrophoretic mobility as a function of pertinent variables: pH, temperature and ionic strength. The adsorption of BSA onto the latex was investigated to identify the conditions at which the adsorbed amount of BSA was negligible. The adsorption of RNA was studied to establish the conditions which give rise to maximal adsorption of RNA. In order to favor the desorption of RNA, desorption was investigated by changing the pH, ionic strength, and temperature. The adsorption of BSA was found to be lower at 20 than at 40 degrees C. However, the adsorption of RNA is drastically affected by the pH and the ionic strength of the medium. Maximal adsorbed amounts were obtained at acidic pH, 20 degrees C, and low ionic strength. The adsorption is shown to decrease when the pH, temperature and ionic strength increase, implying that the adsorption was mainly governed by electrostatic interactions. Maximal release of RNA molecules was obtained at high ionic strength and basic pH.     

Effect of preparation conditions on properties and permeability of chitosan-sodium hexametaphosphate capsules

Capsules were obtained by interpolymer complexation between chitosan (polycation) and sodium hexametaphosphate (SMP, oligoanion). The effect of the preparation conditions on the capsule characteristics was evaluated. Specifically, the influence of variables such as pH, ionic strength, reagent concentration, and additives on the capsule permeability properties was investigated using dextran as a model permeant. The capsule membrane permeability was found to increase by decreasing the chitosan/SMP ratio as well as adding mannitol to the oligoanion recipient bath. Increasing the ionic strength or the pH of the initial chitosan solution was also found to enhance the membrane permeability, moving the membrane exclusion limit to higher values. Generally, the capsules prepared tinder all tested conditions had a relatively low permeability which rarely exceeded a molecular cut-off of 40 kD based on dextran standards. Furthermore, the diffusion rate showed a strong temporal dependence, indicating that the capsules prepared under various conditions exhibit different apparent pore size densities on the surface. The results indicated that, in order to obtain the desired capsule mass-transfer properties, the preparation conditions should be carefully considered and adjusted. Adding a polyol as well as low salt amount (less than 0.15%) is preferable as a means of modulating the diffusion characteristics, without disturbing the capsule mechanical stability.     

羧甲基壳聚糖微球固定化AS1.398中性蛋白酶的制备和性质研究

以戊二醛为交联剂,制备羧甲基壳聚糖微球固定AS1．398中性蛋白酶。研究了羧甲基壳聚糖固定化酶微球的制备条件、固定化酶的适宜温度、pH、米氏常数和储存稳定性等性质。结果表明。在pH=7．0的中性环境下；交联剂与羧甲基壳聚糖摩尔比为0．4：1；干酶与羧甲基壳聚糖的质量比为0．125：1；在室温下交联至少4h。便可得到活力相对较高的固定化酶。自由酶和固定化酶的最适宜温度分别为40℃和65℃。在70℃下，固定化酶的热稳定性比自由酶要好。自由酶和固定化酶的最佳pH分别为7．0和6．0，固定化酶具有较宽的酸碱稳定性，在pH6～8都保持较高活力。固定化酶在5℃和35℃下储存1周后酶相对活力分别为97．6％和85．1％，而没有被固定的自由酶在5℃下储存1周酶相对活力仅为61．3％。自由酶和固定化酶的Km分别为5．66g／L和1．04g／L。     

Effect of preparation conditions on properties and permeability of chitosan–sodium hexametaphosphate capsules

Capsules were obtained by interpolymer complexation between chitosan (polycation) and sodium hexametaphosphate (SMP, oligoanion). The effect of the preparation conditions on the capsule characteristics was evaluated. Specifically, the influence of variables such as pH, ionic strength, reagent concentration, and additives on the capsule permeability properties was investigated using dextran as a model permeant. The capsule membrane permeability was found to increase by decreasing the chitosan/SMP ratio as well as adding mannitol to the oligoanion recipient bath. Increasing the ionic strength or the pH of the initial chitosan solution was also found to enhance the membrane permeability, moving the membrane exclusion limit to higher values. Generally, the capsules prepared under all tested conditions had a relatively low permeability which rarely exceeded a molecular cut-off of 40 kD based on dextran standards. Furthermore, the diffusion rate showed a strong temporal dependence, indicating that the capsules prepared under various conditions exhibit different apparent pore size densities on the surface. The results indicated that, in order to obtain the desired capsule mass-transfer properties, the preparation conditions should be carefully considered and adjusted. Adding a polyol as well as low salt amount (less than 0.15%) is preferable as a means of modulating the diffusion characteristics, without disturbing the capsule mechanical stability.     

Viscosity of polyelectrolyte solutions

The viscosity behaviour of polyelectrolytes in solutions of low ionic strength has been investigated. The dependence of the viscosity on the degree of substitution, the molecular weight and the velocity gradient was studied in detail. The measurements were carried out in solutions of different ionic strength and the limiting intrinsic viscosity at zero ionic strength was determined by extrapolation. It was found that at zero ionic strength the exponent in the KUHN -MARK -HOUWINK equation has the value a = 1.1. It was further found that the intrinsic viscosities in the low and medium molecular weight region were considerably higher than those expected for rigid rodlike molecules of comparable size. The exceptionally high values of the intrinsic viscosity in solutions of low ionic strength indicate the presence of a pronounced “electroviscous effect” in these solutions.     

Degradation of electrospun PLGA-chitosan/PVA membranes and their cytocompatibility in vitro

Nanofibrious composite poly(lactide-co-glycolide) (PLGA) and chitosan/poly(vinyl alcohol) (PVA) membranes were prepared by simultaneously electrospinning PLGA and chitosan/PVA from two different syringes. The in vitro degradation of PLGA and cross-linked composite membranes was examined for up to 10 weeks in phosphate-buffered saline (PBS, pH 7.4) at 37 degrees C. The pH of PBS, the weight average molecular weight of PLGA, fiber morphology and mechanical properties, including tensile strength, Young's modulus and elongation-at-break, were measured as a function of degradation time. The fibrous composite membranes were further investigated as a promising scaffold for human embryo skin fibroblasts (hESFs) culture. The cell adhesion and morphology of hESFs seeded on each electrospun membrane was observed using scanning electron microscope and inverted phase contrast microscopy after Wright-Giemsa staining. The introduction of chitosan/PVA component changed the hydrophilic/hydrophobic balance and, thus, influenced degradation behavior and mechanical properties of the composite membranes during degradation. The cells could not only favorably attach and grow well on the composite membranes, but were also able to migrate and infiltrate the membranes. Therefore, the results suggest that the composite membranes can positively mimic the structure of natural extracellular matrices and have the potential for application as three-dimensional tissue-engineering scaffolds.     

Effect of gamma,ethylene oxide,electron beam,and plasma sterilization on the behaviour of SR-PLLA fibres in vitro

The aim of this study was to evaluate the effect of various sterilization processes on the physical and mechanical properties of self-reinforced bioabsorbable fibres made out of polylactide (PLLA). The samples were sterilized using plasma, ethylene oxide (one and two cycles), gamma (25 kGy at room temperature, 25 kGy in dry ice, and 2 x 25 kGy at room temperature), and electron beam (15, 25, and 55 kGy) sterilization. The intrinsic viscosity, crystallinity, and mechanical properties (modulus of elasticity, yield strength, and ultimate tensile strength) were tested before and immediately after each sterilization treatment, as well as up to 30 weeks in vitro. Compared with unsterilized fibres, the intrinsic viscosity was markedly decreased after radiation sterilization (gamma and electron beam) and the loss in mechanical properties was accelerated during in vitro degradation. Plasma and ethylene oxide (one and two cycles) did not markedly alter the properties of the samples after sterilization or during in vitro degradation. These data are important for determining the effect of various sterilization processes on the physical and mechanical properties of polylactide-based materials and can be used to predict how fast degradation of the mechanical properties of the self-reinforced PLLA will occur. They can also be used to tailor the degradation kinetics to optimize implant design.     

Solution studies of chitosan 6-O-sulfate

Commercial chitosan, and highly deacetylated congeners thereof, can be selectively and extensively sulfated at the O-6 level. Either a 2:1 mixture of sulfuric and chlorosulfonic acid (Method I) or a pyridine-SO₃ complex, following protection of the 2-NH₂ and 3-OH groups with copper ions (Method II), can be used. The properties of sulfated chitosan with different degrees of acetylation are studied at pH conditions which promote a polyampholyte structure. Light scattering and intrinsic viscosity ([η]) measurements of chitosan 6-O-sulfate with a degree of acetylation of 20%, prepared by Method II, indicate the presence of molecular and structural heterogeneity, probably due to ordered structures in highly acetylated regions of the parent chitosan. This hypothesis is confirmed by the NMR analysis of the fragments obtained by depolymerization with nitrous acid. The heterogeneity is not observable in compounds obtained by Method I and in highly deacetylated chitosan 6-O-sulfate. The [η] increase of the polyampholyte on decreasing ionic strength can be explained in terms of a more rigid conformation stabilized by electrostatic interactions between the sulfate groups and the protonated amino groups on neighbouring residues.     

Chitosan/polyethylene glycol blend fibers and their properties for drug controlled release

Fibers of chitosan and polyethylene glycol (PEG), with salicylic acid as model drug incorporated in different concentrations, were obtained by spinning their solution through a viscose-type spinneret into a coagulating bath containing aqueous tripolyphosphate and ethanol. Chemical, morphological, and mechanical properties characterization were carried out, as well as the studies of the factors that influence the drug releasing from chitosan/PEG fibers. These factors included the component ratio of chitosan and PEG, the loaded amount of salicylic acid, the pH and the ionic strength of the release solution and others. The diameter of the fibers is around 15 +/- 3 microm. The best values of the tensile strength at 12.86 cN/tex and breaking elongation at 21.13% of blend fibers were obtained when the PEG content was 8 and 5 wt %, respectively; the water-retention value of blend fibers increased as the composition of PEG was raised. The results of controlled release tests showed that the amount of salicylic acid released increased with an increase in the proportion of PEG present in the fiber. Moreover, the release rate of drug decreased as the amount of drug loaded in the fiber increased, but the cumulative release amount is increasing. The chitosan/PEG fibers were also sensitive to pH and ionic strength. The release rate was being accelerated by a lower pH and a higher ionic strength, respectively. All the results indicated that the chitosan/PEG fiber was potentially useful in drug delivery systems.