低分子量壳聚糖的研制

研究了在酸性条件下过氧化氢对壳聚糖的氧化降解反应，讨论了过氧化氢浓度、温度及反应时间对氧化降解反应的影响。结果表明，用过氧化氢使壳聚糖氧化降解是制备药用低分子量壳聚糖的一种简便易行的方法。     

壳聚糖分子参数对羟基喜树碱包衣脂质体体外性质的影响研究

目的研究不同脱乙酰度(DD)及不同相对分子质量(Mr)的壳聚糖(CS)对CS包衣羟基喜树碱(HCPT)脂质体的体外性质的影响,为选择具有合适分子参数的壳聚糖作为该制剂的包衣材料提供实验基础.方法采用过氧化氢氧化降解的方法制备不同Mr的CS;利用N-乙酰基取代法制备不同DD的CS.采用薄膜分散法制备HCPT脂质体,并用不同分子参数的CS包衣.对其形态、zeta电位、平均粒径、包封率及体外释药特性做了考察.结果CS包衣HCPT脂质体外观均呈球形,粒径均匀.未包衣脂质体zeta电位为(-46.8±1.0)mV(n=10),经CS包衣后,zeta电位均变为正值,且随着DD的降低而变小,而Mr对zeta电位无显著影响.DD对脂质体的平均粒径无显著性影响,而随着Mr的降低而减小.CS包衣脂质体的包封率随着CS的Mr和DD的降低而减小,体外释药速度随着DD及Mr的降低而加快.结论CS的分子参数对CS包衣HCPT脂质体的体外性质有较大的影响,且成一定规律性,可通过调整CS分子参数得到不同体外性质的CS包衣HCPT脂质体.     

微波辐射快速制备水溶性壳聚糖

目的快速制备水溶性壳聚糖。方法利用微波辐射 ,用过氧化氢作氧化剂 ,非均相降解高分子量壳聚糖。设计了正交试验法 ,得到最优化反应条件。结果最优反应条件为 5 %过氧化氢、5 %壳聚糖 ,微波辐射功率约40 0W ,辐射 3min ,所得水溶性壳聚糖分子量为 1 .1× 1 0 4 D ,收率可达 60 %。结论微波法制备低聚壳聚糖效果理想 ,可进一步扩展到壳聚糖的其它化学修饰     

壳聚糖负载肉桂挥发油纳米粒制备工艺响应面法优化及质量评价

目的:优化壳聚糖负载肉桂挥发油纳米粒的制备工艺和处方,并对其质量进行评价。方法:采用单因素考察壳聚糖纳米粒制备的处方和工艺,以粒径、包封率和载药量为评价指标,应用星点设计-响应面法优化负载肉桂挥发油的壳聚糖纳米颗粒的制备工艺,采用透射电镜观察肉桂挥发油壳聚糖纳米粒形态,并对其稳定性进行研究。结果:壳聚糖负载肉桂挥发油纳米粒优化后的工艺为壳聚糖浓度0.2%,均质压力为500 bar(1 bar=0.1 MPa),循环次数为20次,TPP含量0.2 mg·mL^-1,在该条件下平均包封率为(83.37±0.40)%、平均载药量为(26.42±0.65)%、平均粒径为(248.5±12.2) nm, Zeta电位为(52.3±1.1) mV。透射电镜结果显示其呈粒径均匀的类球形,且肉桂油外包裹着一层壳聚糖。稳定性结果显示壳聚糖负载肉桂挥发油纳米粒混悬液在低温条件下贮存最佳。结论:负载肉桂挥发油壳聚糖纳米粒,制备工艺简单,可重复性较好,物理稳定性较好。     

复方茵柏合剂壳聚糖澄清工艺研究

目的研究壳聚糖澄清法用于复方茵柏合剂的除杂效果以及制备工艺的可行性。方法以绿原酸为评价指标，通过正交设计优选澄清条件，与原制备工艺比较，并进行稳定性试验。结果壳聚糖澄清法所制备样品中绿原酸含量、薄层色谱鉴别与原工艺比较均无显著差异，且澄清度和稳定性均优于原工艺。结论壳聚糖澄清法具有简化工艺、缩短生产周期、提高制剂稳定性等优点，可用于复方茵柏合剂的制备。     

低相对分子质量透明质酸的制备及其促血管生成作用

目的观察2种降解方法制备的低相对分子质量(Mr)透明质酸(LMWHA)对血管生成的影响。方法采用过氧化氢氧化降解和透明质酸酶酶解的方法制备LMWHA,利用鸡胚绒毛尿囊膜(CAM)模型观察LMWHA对血管生成的影响。结果Mr不同的LMWHA,其对CAM血管生成的影响也不同;Mr低于10000的LMWHA对CAM血管生成的影响与溶剂对照组相比,差异有非常显著性意义(P<0.01)。结论Mr低于10000的LMWHA具有促进CAM血管生成的作用。     

甘草酸表面修饰N-己酰化壳聚糖纳米粒的制备及其稳定性研究

目的:制备N-己酰化壳聚糖纳米粒(CCS-NPs)和甘草酸表面修饰N-己酰化壳聚糖纳米粒(CCS-NPs-GL),并考察其稳定性。方法:应用离子凝胶法制备CCS-NPs,高碘酸盐氧化法制备CCS-NPs-GL;考察各纳米粒在冷冻干燥前、后和不同pH缓冲盐中粒径、电位的变化以及不同温度对CCS-NPs-GL的粒径、药物包封率和甘草酸结合率的影响。结果:CCS-NPs和CCS-NPs-GL在冷冻干燥后粒径稍有增大,缓冲盐溶液中迅速分散,电位下降不明显;在生理pH条件下,两者易于分散且粒径无明显变化;不同温度下,CCS-NPs-GL的粒径、药物包封率和甘草酸结合率无明显变化。结论:CCS-NPs-GL作为潜在的肝靶向主动传输载体,其粒子的稳定性可满足后续静脉给药的体内靶向研究和药效学评价。     

不同分子量和脱乙酰度壳聚糖用作组织工程材料的性质评价

目的对不同相对分子质量(Mr)和脱乙酰度的壳聚糖用于组织再生修复的前景进行评价。方法MTT法测定Mr为5万,20万,50万,100万,脱乙酰度分别为85%和95%的8种壳聚糖对骨髓间充质干细胞的亲和性,测定它们在体外、体内的降解特性,并通过检测接触角考察了它们的亲水性。结果在所研究的8种壳聚糖中,Mr为50万和100万,脱乙酰度为95%的壳聚糖更利于骨髓间充质干细胞的黏附生长,亲水性较强,在体内埋植8~16周后仍能保持形态完整,利于种子细胞生存。结论Mr为50万和100万,脱乙酰度为95%的壳聚糖能够与骨髓间充质干细胞复合用于组织再生修复。     

壳聚糖膜的制备及其稳定性研究

将不同性能的壳聚糖制膜并研究了其稳定性。结果表明,壳聚糖膜可生物降解,其降解速度与介质pH、溶菌酶等因素有关。     

壳聚糖-岩藻聚糖硫酸酯纳米粒的制备及性质研究

目的：本文以低分子量岩藻聚糖硫酸酯为交联剂,研究了聚电解质凝聚法制备壳聚糖-岩藻聚糖硫酸酯纳米微粒(Chitosan-fucoidan nanoparticles, CS-Fuc NPs)的制备工艺,并对纳米粒的胃肠道和贮藏稳定性进行研究。方法：采用聚电解质凝聚法制备壳聚糖-岩藻聚糖硫酸酯纳米微粒,采用体外模拟胃液和模拟肠液消化体系,检测纳米粒的胃肠稳定性,常温贮藏实验测定纳米粒的短期贮藏稳定性。结果：壳聚糖-岩藻聚糖硫酸酯纳米微粒的最优制备条件是：壳聚糖(1mg/ml)与岩藻聚糖硫酸酯(1mg/ml)体积比为1.1/1,pH 4.5,温度30℃。所得纳米粒粒径为227.8 nm,Zeta电位为38.4 mV,PDI为0.231,岩藻聚糖硫酸酯复合率(Fuc%)为94.92%。所制备的纳米颗粒在10周内没有显著变化,在模拟胃环境中稳定性良好,在模拟肠道环境中解聚性良好。结论： 壳聚糖-岩藻聚糖硫酸酯纳米粒制备工艺简单,性能良好,有望成为新型的口服药物运送载体。     

Characterization of chitosan and its derivatives using asymmetrical flow field-flow-fractionation: a comparison with traditional methods

Chitosan and its derivatives are an important group of polymers used extensively in pharmaceutics. Thus, their physicochemical properties are of considerable interest and need to be characterized carefully. The most important feature to determine is their molecular weight and molecular weight distribution while the molecular weight of polymers plays an important role as pharmaceutical excipients. In this study, the feasibility of using asymmetrical flow field-flow-fractionation (AF4) connected online to a multi-angle light scattering (MALS) detector to measure the molecular weight of chitosans, trimethyl chitosans were studied and compared with the results from some traditional measurement methods. It was found that the influence of trimethyl chitosan synthesis process on the resulting molecular weight decrease depends on the initial molecular weight of chitosan. Significant molecular weight decrease was observed when chitosan molecular weight was larger than 100 kDa. In contrast, the influence was marginal when the molecular weight of chitosan was less than 50 kDa. The AF4-MALS was found to be a suitable method for the characterization of pure chitosans and trimethyl chitosans.     

Effect of chitosan structure properties and molecular weight on the intranasal absorption of tetramethylpyrazine phosphate in rats

The objective of this work was to assess and compare the absorption promoting effect of different molecular-weight chitosans, trimethyl chitosans and thiolated chitosans for intranasal absorption of 2,3,5,6-tetramethylpyrazine phosphate (TMPP). An in situ nasal perfusion technique in rats was utilized to test the rate and extent of TMPP absorption in situ. In vivo studies were carried out in rats and the pharmacokinetic parameters were calculated and compared with that of intravenous injection. All the chitosan derivatives investigated could enhance the intranasal absorption of TMPP significantly. However, thiolation could not improve the absorption-enhancing capacity of chitosan remarkably even when the thiolation ratio was as high as 152 μmol/g. In contrast, trimethylated chitosan exhibited stronger absorption-enhancing ability than the homopolymer chitosan. The permeation enhancing effect of chitosan increased with increasing molecular weight up to M_w 100 kDa. In vivo studies indicated that chitosan 100 kDa and TMC 50 kDa had comparable absorption-enhancing effect but chitosan 100 kDa functioned for more than 120 min versus 90 min for TMC. A good correlation was found between the in situ absorption data and plasma concentration in vivo for the polymers investigated. This study demonstrated that both chitosan structural features and chitosan molecular weight play a key role on promoting the intranasal absorption of TMPP. Taking safety reason into account, chitosan 100 kDa is the most promising as an intranasal absorption enhancer.     

Physical properties of chitosan dispersions in glycolic acid

Evaporation-freezing and rheological behaviour of chitosan dispersions at different temperatures and with different molecular weights using glycolic acid as anionic systems were studied. Chitosans of high, 2,000,000, medium, 750,000, and low, 70,000 molecular weight (hC, mC, and lC, respectively) were employed alone or as mixtures (hC/mC, hC/lC, and mC/lC 1:1, w/w). Different concentrations of glycols were added to these base dispersions (propylene glycol and glycerine) to investigate how the above physical properties change. The different rheological and evaporation-freezing behaviours of chitosan dispersions were related both to the molecular weight of chitosan and the vehicle composition of the dispersions. Particularly, the rheological study showed a pseudoplastic and shear thinning behaviour for all chitosan dispersions with flow index values n, tending to <1 at increasing molecular weights. Chitosans dispersions containing glycols showed lower apparent viscosity values than the base dispersions of the corresponding chitosans, but the water loss and the freezing point were lower especially for chitosan dispersions containing glycerine. This work presents a wide range of dispersion series from which to choose the most suitable to formulate pharmaceutical and cosmetic products.     

Mucoadhesive chitosan-coated liposomes: characteristics and stability

Lecithin liposomes, empty or containing FITC-dextran, were prepared by the ethanol injection method. Three different types of chitosans with different molecular weight and degrees of deacetylation were used (Seacure 113, 210 and 311). Chitosan coating was carried out by mixing the liposomal suspension with the chitosan solution followed by incubation. The size of liposomes was measured before and after polymer coating by an image analysis technique. The mean diameter of liposomes containing FITC-dextran was in the size range 250-280nm, whereas the size after coating was 300-330nm, regardless of chitosan type. All chitosan-coated liposomes were of spherical shape and no morphological differences between uncoated and coated liposomes were observed. Liposomes with FITC-dextran, originally entrapping 50% of the marker substance taken in the preparation and coated in the presence of unentrapped marker substance, contained 60-65%of the marker substance. The highest entrapment was found for liposomes coated with medium molecular weight chitosan. The stability of chitosan-coated liposomes in simulated gastric fluid was significantly higher as compared to uncoated liposomes. One can conclude that chitosan is stabilizing the original liposomal structure and protecting liposomally entrapped drug.     

壳聚糖及其衍生物体外抗幽门螺杆菌作用及影响因素

目的研究壳聚糖及其衍生物在体外对幽门螺杆菌(Hp)的抑菌作用及其影响因素。方法采用打孔法检测了不同浓度、pH值、脱乙酰度壳聚糖及羧甲基壳聚糖在体外对Hp的抑菌作用。结果①壳聚糖和羧甲基壳聚糖在体外对3株Hp标准菌株具有普遍的抑菌作用;②在pH 6~4范围内,随pH值降低,抗菌作用增强,差异有显著性(P<0.01),最佳pH值为4;③70%、88.5%脱乙酰度壳聚糖及羧甲基壳聚糖的抗Hp作用差异有显著性(P<0.01~0.05),抑菌强度依次为DD70壳聚糖、DD88.5壳聚糖和羧甲基壳聚糖;④在质量浓度为10 g.L-1~50 g.L-1范围内羧甲基壳聚糖抗Hp作用差异无显著性;在质量浓度为5 g.L-1~20 g.L-1范围内70%、88.5%脱乙酰度壳聚糖抗Hp作用差异也无显著性(P>0.05)。结论①壳聚糖和其衍生物对Hp有普遍的抑菌作用;②壳聚糖及其衍生物的抗Hp作用受多种因素影响,其中pH值对壳聚糖抗菌作用的影响最为明显,在pH值6~4范围内,壳聚糖的抗菌活性随着pH值的下降而增强;③壳聚糖的脱乙酰度、结构(化学修饰)及分子量也影响壳聚糖的抗菌活性,不同的细菌所要求的脱乙酰度、修饰基团和分子量有着明显的差异。     

Mucoadhesive chitosan-coated liposomes: characteristics and stability

Lecithin liposomes, empty or containing FITC-dextran, were prepared by the ethanol injection method. Three different types of chitosans with different molecular weight and degrees of deacetylation were used (Seacure 113, 210 and 311). Chitosan coating was carried out by mixing the liposomal suspension with the chitosan solution followed by incubation. The size of liposomes was measured before and after polymer coating by an image analysis technique. The mean diameter of liposomes containing FITC-dextran was in the size range 250-280 nm, whereas the size after coating was 300-330 nm, regardless of chitosan type. All chitosan-coated liposomes were of spherical shape and no morphological differences between uncoated and coated liposomes were observed. Liposomes with FITC-dextran, originally entrapping 50% of the marker substance taken in the preparation and coated in the presence of unentrapped marker substance, contained 60-65% of the marker substance. The highest entrapment was found for liposomes coated with medium molecular weight chitosan. The stability of chitosan-coated liposomes in simulated gastric fluid was significantly higher as compared to uncoated liposomes. One can conclude that chitosan is stabilizing the original liposomal structure and protecting liposomally entrapped drug.     

Low molecular weight chitosan inhibits obesity induced by feeding a high-fat diet long-term in mice

Three low molecular weight chitosans (molecular weight: 21, 46 and 130 kDa) obtained by enzymatic hydrolysis of a high molecular weight chitosan (average molecular weight: 650 kDa) had low viscosity and were water-soluble. The effects of these water-soluble chitosans on pancreatic lipase (in-vitro) and the elevation of plasma triacylglycerol concentration after the oral lipid tolerance test were examined in mice. The water-soluble 46-kDa chitosan was the most effective at inhibiting pancreatic lipase activity (in-vitro) and plasma triacylglycerol elevation after the oral lipid tolerance test. Based on this result, the effects of the 46-kDa chitosan on increases in bodyweight, various white adipose tissue weights, and plasma and liver lipids were examined in mice fed a high-fat diet for 20 weeks. Water-soluble 46-kDa chitosan (300 mg kg(-1), twice daily) prevented increases in bodyweight, various white adipose tissue weights and liver lipids (cholesterol and triacylglycerol) in mice fed a high-fat diet, and further increased the faecal bile acid and fat. The results suggest that the lipid-lowering effects of the 46-kDa chitosan may be mediated by increases in faecal fat and/or bile acid excretion resulting from the binding of bile acids, and by a decrease in the absorption of dietary lipids (triacylglycerol and cholesterol) from the small intestine as a result of the inhibition of pancreatic lipase activity. Water-soluble 46-kDa chitosan (100 and 300 mg kg(-1), twice daily) did not cause liver damage with the elevation of glutamic oxaloacetic transaminase and glutamic pyruvic transaminase, or kidney damage with the elevation of blood nitrogen urea. It was concluded that water-soluble 46-kDa chitosan is a safe functional food.     

Thermosensitive hydrogels for nasal drug delivery: The formulation and characterisation of systems based on N-trimethyl chitosan chloride

Towards the development of a thermosensitive drug-delivery vehicle for nasal delivery, a systematic series of N-trimethyl chitosan chloride polymers, synthesised from chitosans of three different average molecular weights, have been co-formulated into a hydrogel with poly(ethylene glycol) and glycerophosphate. Rheological evaluations have shown that hydrogels derived from N-trimethyl chitosan with a low degree of quaternisation and high or medium average molecular weight exhibit relatively short sol-gel transition times at physiologically relevant temperatures. Also, the same hydrogels display good water-holding capacity and strong mucoadhesive potential, and their mixtures with mucus exhibit rheological synergy. An aqueous hydrogel formulation, derived from N-trimethyl chitosan of medium average molecular weight and low degree of quaternisation, appears particularly promising in that it exhibits most favourable rheological and mucoadhesive behaviour and a sol-gel transition that occurs at 32.5 °C within 7 min.     

Chitosans as absorption enhancers of poorly absorbable drugs: 3: Influence of mucus on absorption enhancement

Chitosans are potent nontoxic absorption enhancers after nasal administration but their effects on the intestinal epithelium in vivo has not been studied in detail. In this study, the effects of chitosans with varying molecular weights and degrees of acetylation on the absorption of a poorly absorbed model drug (atenolol) were studied in intestinal epithelial cell layers with or without a mucus layer and in an in situ perfusion model of rat ileum. The effects of the chitosans on epithelial morphology and release of lactate dehydrogenase (LDH) into the perfusate were investigated in the in situ model. The chitosans had pronounced effects on the permeability of mucus-free Caco-2 layers and enhanced the permeation of atenolol 10- to 15-fold, with different absorption kinetics for different chitosans, in accordance with previous results. In contrast, enhancement of atenolol absorption through rat ileum was modest. LDH release from the tissues perfused with chitosans did not increase, indicating that the chitosans were used at nontoxic concentrations. Morphological examination of the perfused ileal tissues revealed more mucus discharge from the tissues exposed to chitosans than from controls, which suggested that the discharged mucus may inhibit the binding of chitosan to the epithelial surface and hence decrease the absorption-enhancing effect. This hypothesis was supported by studies with intestinal epithelial HT29-H goblet cells covered with a mucus layer. The binding of chitosan to the epithelial cell surface and subsequent absorption-enhancing effects were significantly reduced in mucus-covered HT29-H cultures. When the mucus layer was removed prior to the addition of chitosan, the cell surface binding and absorption-enhancing effects of the chitosans were increased. We conclude that the modest absorption-enhancing effects of unformulated chitosan solutions in the perfused rat ileum are a result of the mucus barrier in this tissue. This effect may be overcome by increasing the local concentrations of both chitosan and drug, i.e,. through formulation of the chitosan into a particulate dosage form.     

Potential of low molecular mass chitosan as a DNA delivery system: biocompatibility, body distribution and ability to complex and protect DNA

Cationic polymers have the potential for DNA complexation and it is recognised that they may be useful as non-viral vectors for gene delivery. Highly purified chitosan fractions of < 5000 Da (N1), 5000-10,000 Da (N2) and > 10,000 Daltons (N3) were prepared and characterised in respect of their cytotoxicity, ability to cause haemolysis, ability to complex DNA as well as to protect DNA from nuclease degradation. Also the biodistribution of 125I-labelled chitosans was followed at 5 and 60 min after intravenous injection into male Wistar rats. All chitosan fractions displayed little cytotoxicity against CCRF-CEM and L132 cells (IC50 > 1 mg/ml), and they were not haemolytic (< 15% lysis after 1 and 5 h). Chitosan-DNA interaction at a charge ration of 1:1 was much greater than seen for poly(L-lysine) and complexation resulted in inhibition of DNA degradation by DNase II: 99.9 +/- 0.1, 99.1 +/- 1.5 and 98.5 +/- 2.0% for N1, N2 and N3, respectively. After intravenous injection, all the chitosans showed rapid blood clearance, the plasma levels at 1 h being 32.2 +/- 10.5% of recovered dose for N1 and 2.6 +/- 0.5% of recovered dose for N3. Liver accumulation was molecular mass dependent, being 26.5 +/- 4.9% of the recovered dose for N1 and 82.7 +/- 1.9% of the recovered dose for N3. The observations that the highly purified chitosan fractions used were neither toxic nor haemolytic, that they have the ability to complex DNA and protect against nuclease degradation and that low molecular weight chitosan can be administered intravenously without liver accumulation suggest there is potential to investigate further low molecular weight chitosans as components of a synthetic gene delivery system.