Preparation and anticoagulant activity of a low-molecular-weight sulfated chitosan

Synthesis of chitosan sulfates with low molecular weight (M_v 9000–35,000 Da) was carried out by sulfation of low molecular weight chitosan (M_v 10,000–50,000 Da). The oleum was used as sulfating agent and dimethylfornamide as medium. The chitosans were prepared by enzymatic and acidic hydrolysis of initial high molecular weight chitosan as well as by extrusion solid-state deacetylation of chitin. As was shown by FT-IR and NMR-methods and elemental analysis, the sulfation occurred at C-6 and C-3 positions and substitution degree is 1.10–1.63. The molecular weight sulfated chitosan was determined by viscometric method and the Mark–Houwink equation [η]=10⁻⁵ 4.97 M^0.77. Study of anticoagulant activity showed that chitosan sulfates with lowered molecular weight demonstrated a regular increase of anti-Xa activity like heparins.     

Hydrogel coated monoliths for enzymatic hydrolysis of penicillin G

The objective of this work was to develop a hydrogel-coated monolith for the entrapment of penicillin G acylase (E. coli, PGA). After screening of different hydrogels, chitosan was chosen as the carrier material for the preparation of monolithic biocatalysts. This protocol leads to active immobilized biocatalysts for the enzymatic hydrolysis of penicillin G (PenG). The monolithic biocatalyst was tested in a monolith loop reactor (MLR) and compared with conventional reactor systems using free PGA, and a commercially available immobilized PGA. The optimal immobilization protocol was found to be 5 g l(-1) PGA, 1% chitosan, 1.1% glutaraldehyde and pH 7. Final PGA loading on glass plates was 29 mg ml(-1) gel. For 400 cpsi monoliths, the final PGA loading on functionalized monoliths was 36 mg ml(-1) gel. The observed volumetric reaction rate in the MLR was 0.79 mol s(-1) m(-3) (monolith). Apart from an initial drop in activity due to wash out of PGA at higher ionic strength, no decrease in activity was observed after five subsequent activity test runs. The storage stability of the biocatalysts is at least a month without loss of activity. Although the monolithic biocatalyst as used in the MLR is still outperformed by the current industrial catalyst (immobilized preparation of PGA, 4.5 mol s(-1) m(-3) (catalyst)), the rate per gel volume is slightly higher for monolithic catalysts. Good activity and improved mechanical strength make the monolithic bioreactor an interesting alternative that deserves further investigation for this application. Although moderate internal diffusion limitations have been observed inside the gel beads and in the gel layer on the monolith channel, this is not the main reason for the large differences in reactor performance that were observed. The pH drop over the reactor as a result of the chosen method for pH control results in a decreased performance of both the MLR and the packed bed reactor compared to the batch system. A different reactor configuration including an optimal pH profile is required to increase the reactor performance. The monolithic stirrer reactor would be an interesting alternative to improve the performance of the monolith-PGA combination.     

血清白蛋白在多聚阳离子－壳聚糖共混材料表面的构象变化及其与细胞生长的关系

用L-多聚赖氨酸、聚乙烯亚胺及L-多聚鸟氨酸三种多聚阳离子对壳聚糖进行共混修饰,制备了三种共混材料.在这些材料表面吸附了血清白蛋白,并利用圆二色(CD)光谱研究了白蛋白吸附到材料表面后的构象变化.结果显示,与天然状态相比,白蛋白吸附到共混材料表面后,其α-螺旋、β-折叠及无规则卷曲的含量均发生了明显改变.通过研究MC3T3-E1细胞在这些材料表面的生长情况,发现细胞的增殖与血清白蛋白的构象变化有一定关系,在吸附的白蛋白构象与天然构象最接近的共混材料表面,MC3T3-E1细胞增殖水平最高.     

羧甲基壳聚糖对口腔重要厌氧菌的抑菌性能评价

目的 :评价羧甲基壳聚糖对口腔重要厌氧菌的抑菌性能。方法 :选择与口腔疾病密切相关的厌氧菌 11株 ,采用梯度稀释法测定羧甲基壳聚糖的最低抑菌浓度 (MIC)。结果 :羧甲基壳聚糖对牙龈卟啉菌、放线共生放线菌、中间普氏菌、牙龈嗜二氧化碳纤维菌、黄褐嗜二氧化碳纤维菌、产黑色素普氏菌、白色念珠菌、牙髓卟啉菌、小齿普氏菌、变形链球菌、远缘链球菌、粘性放线菌的 MIC分别为 2 0 ,10 ,5,80 ,2 0 ,>80 ,2 0 ,5,2 0 ,10 ,60 ,40 mg/ml。结论 :羧甲基壳聚糖对多数与口腔疾病密切相关的厌氧菌有一定抑制作用 ,而对产黑色素普氏菌的抑菌性不明显     

几丁聚糖作生物涂层的潜在应用

本文综述了生物涂层的作用、种类和应用,阐述了亲水生物涂层的机理和应用,介绍了几丁聚糖的基本性能和国内外近年来用几丁聚糖作为涂层膜的研究现状,同时探索了几丁聚糖对医疗装置进行生物涂层的可能性,并预测了其潜在应用。     

Elicitation of different Panax ginseng transformed root phenotypes for an improved ginsenoside production

We tested the effect of the presence in the culture medium of chitosan, vanadyl sulfate or methyl jasmonate on growth and ginsenoside production of three stable hairy root lines of Panax ginseng C.A. Meyer showing different morphological phenotypes C-M, HR-M and T-M. The response depended upon line phenotype, specificity of the elicitor and the stage of growth at which the lines were treated. The highest ginsenoside yield was found when methyl jasmonate was added during the progressive deceleration growth phase (on day 25 of culture). In this case, the ginsenoside content reached at the end of the culture (day 28) by root lines C-M, HR-M and T-M was, respectively, 2, 1.8 and 4 times higher than the highest content achieved, also at the end of the culture, by the corresponding untreated root lines. Under the same conditions, the ginsenoside content in the presence of vanadyl sulfate also increased considerably, while with chitosan it clearly decreased. The ginsenoside pattern in response to the presence of the elicitors is also considered.     

Repeated Enzymatic Hydrolysis of Polygalacturonic Acid, Chitosan and Chitin Using a Novel Reversibly-soluble Pectinase with the Aid of κ-carrageenan

Aspergillus niger pectinase, together with κ-carrageenan, could be precipitated in the presence of 0.2% KCl and re-dissolved by ten-fold dilution of the salt. The free as well as this reversibly-soluble (rs) enzyme were evaluated for hydrolysis of polygalacturonic acid, chitosan and chitin. The rs-enzyme showed 92%, 80% and 74% activity (as compared to the corresponding amount of enzyme when present as a free enzyme) towards the three substrates, respectively. There was no significant change in the pH and temperature optima of the rs-enzyme. This preparation could be reused six times without loss of any detectable polygalacturonase activity. This biocatalyst design was found to be efficient for the hydrolysis of polygalacturonic acid, chitosan and chitin.     

Antioxidant properties of some different molecular weight chitosans

Chitosan, a cationic polysaccharide, is widely employed as dietary supplement and in pharmacological and biomedical applications. Although numerous studies have focused on its applications as pharmaceutical excipients or bioactive reagents, relationships between molecular weight (Mr) and biological properties remain unclear. The focus of this study was on the antioxidant properties of several Mr chitosans. We measured the ability of seven Mr chitosans (CT1; 2.8 kDa, CT2; 17.0 kDa, CT3; 33.5 kDa, CT4; 62.6 kDa, CT5; 87.7 kDa, CT6; 604 kDa, CT7; 931 kDa) to protect plasma protein from oxidation by peroxyl radicals derived from 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH). A comparison of the antioxidant action of high Mr chitosans (CT6–CT7) with that of low Mr chitosans (CT1–CT5) showed that low Mr chitosans (CT1–CT5) were more effective in preventing the formation of carbonyl groups in plasma protein exposed to peroxyl radicals. AAPH substantially increases plasma protein carbonyl content via the oxidation of human serum albumin (HSA). We also measured the ability of these chitosans to protect HSA against oxidation by AAPH. Low Mr chitosans (CT1–CT5) were found to effectively prevent the formation of carbonyl groups in HSA, when exposed to peroxyl radicals. Low Mr chitosans were also good scavengers of N-centered radicals, but high Mr chitosans were much less effective. We also found a strong correlation between antioxidant activity and the Mr of chitosans in vitro. These activities were also determined by using the ‘TPAC’ test. These results suggest that low Mr chitosans (CT1–CT3) may be absorbed well from the gastrointestinal tract and inhibit neutrophil activation and oxidation of serum albumin that is frequently observed in patients plasma undergoing hemodialysis, resulting in a reduction in oxidative stress associated with uremia.     

Ethylenesulfide as a useful agent for incorporation into the biopolymer chitosan in a solvent-free reaction for use in cation removal

Chitosan (Ch) was chemically modified with ethylenesulfide (Es) under solvent-free conditions to give (ChEs), displaying a high content of thiol groups due to opening of the three member cyclic reagent. Elemental analysis showed a decrease in nitrogen content. This result indicated the incorporation of two ethylenesulfide molecules for each unit of the polymeric structure of the precursor biopolymer. Infrared spectroscopy, thermogravimetry, and ¹³C NMR in the solid state demonstrated the effectiveness of the reaction, with signals at 30 ppm for ChEs due to the change in the methylene group environment. Divalent metal uptake by chemically modified biopolymer gave the order Cu > Ni > Co > Zn, reflecting the corresponding acidity of these cations in bonding to the sulfur and the basic nitrogen atoms available on the pendant chains. The equilibrium data were fitted to Freundlich, Temkin, and Langmuir models. The maximum monolayer adsorption capacity for the cations was found to be 1.54 ± 0.02, 1.25 ± 0.03, 1.13 ± 0.01, and 0.83 ± 0.03 mmol g⁻¹, respectively. The Langmuir model best explained the cation–sulfur bond interactions at the solid–liquid interface. The thermodynamics for these interactions gave exothermic enthalpic values of −43.02 ± 0.03, −28.72 ± 0.02, −26.27 ± 0.04, and −17.32 ± 0.02 kJ mol⁻¹, respectively. The spontaneity of the systems is given by negative Gibbs free energies of −31.2 ± 0.1, −32.7 ± 0.1, −31.7 ± 0.1, and −32.2 ± 0.1 kJ mol⁻¹, respectively, in spite of the unfavorable negative entropic values of −39 ± 1, −13 ± 1, −18 ± 1, and −49 ± 1 J K⁻¹ mol⁻¹ due to solvent ordering in the course of complexation. This newly synthesized biopolymer is presented as a chemically useful material for cation removal from aqueous solution.     

Chitosan-LiOH-urea aqueous solution—a novel water-based system for chitosan processing

A solution of partially N-deacetylated chitosan in aqueous lithium hydroxide (LiOH)/urea was prepared successfully through a freeze-thawing process and the dissolution behavior was studied. The results indicated that chitosan can directly dissolve in LiOH/urea aqueous solution. LiOH mainly contributed to the breakage of intramolecular and intermolecular hydrogen bonds in chitosan. Urea, LiOH, and chitosan formed inclusion compound (IC) with urea as the IC host, and the LiOH-chitosan complex as the guest. Aqueous 4.8 wt % LiOH/8.0 wt % urea was verified to be the optimal solvent for chitosan. The results of rheology and viscosity characterizations revealed that chitosan/4.8 wt % LiOH/8.0 wt % urea aqueous solution was pseudoplastic fluid, and was more stable than the solution of chitosan in acetic acid at ambient temperature.