甘油三酯介质中制备壳聚糖纳米粒工艺研究

用乳化溶剂扩散法结合离子沉淀交联法从甘油三酯介质中制备壳聚糖纳米粒,用L9(34)正交设计优选纳米粒制备的处方工艺条件,用显微镜测定纳米粒的粒径,用透射电镜观察纳米粒的形态。结果:正交设计确定纳米粒制备的最优处方工艺条件为:搅拌速度150 r.min-1,壳聚糖质量分数0.10%,壳聚糖分子量9.1万,甘油三酯与壳聚糖酸溶液体积之比200:1,制备的纳米粒平均粒径为(150±50)nm。甘油三酯介质中制备壳聚糖纳米粒工艺简便,制剂具有广泛应用前景。     

区域选择性改性的纤维素和壳聚糖衍生物及其血液相容性

通过对纤维素和壳聚糖的区域选择性改性,将内皮细胞表面硫酸乙酰肝素（ES—HS）分子结构中对其血液相容性有重要影响的官能团引入纤维素和壳聚糖的分子结构中,并将其通过离子键固定在部分阳离子化的纤维素膜上,以期模拟ES—HS的血液相容性。血小板吸附结果表明,6位改性的纤维素衍生物的吸附程度较高。在五种壳聚糖衍生物中,2位的NS03／NAc为6／4的衍生物表现出最低的血小板吸附。当保持壳聚糖2位的NS03／NAc值不变时,对6位进行完全磺酸酯化,也可有效减少血小板的吸附。     

Investigation of PVA/ws-chitosan hydrogels prepared by combined γ-irradiation and freeze-thawing

γ-Irradiation combined with freeze-thawing, i.e. irradiation followed by freeze-thawing and freeze-thawing followed by irradiation, was applied to prepare poly(vinyl alcohol) (PVA)/water soluble chitosan (ws-chitosan) hydrogels for wound dressing. The properties of these hydrogels were investigated and compared to those prepared by freeze-thawing and by irradiation, respectively. Hydrogels made by irradiation followed by freeze-thawing show larger swelling capacity and mechanical strength, higher thermal stability, lower water evaporation rate, and are less turbid than those made by pure freeze-thawing and freeze-thawing followed by irradiation. Hydrogels made by irradiation alone cannot be used as wound dressing due to their poor mechanical strength. SEM results show that the final structure of hydrogels made by combined irradiation and freeze-thawing is mainly determined by the first processing step. It is found that the appropriate amount of ws-chitosan can endow hydrogels with large swelling capacity and mechanical strength. The presence of ws-chitosan provides the hydrogels with good antibacterial activity against Escherichia coli (E. coli).     

The influence of molecular weight of quaternized chitosan on antifungal activity

Quaternized chitosan derivatives with different molecular weights were synthesized in the laboratory. Subsequent experiments were conducted to test their antifungal activities against Botrytis cinerea Pers. (B. cinerea pers.) and Colletotrichum lagenarium (Pass) Ell.et halst (C. lagenarium (Pass) Ell.et halst). Our results indicate that quaternized chitosan derivatives have stronger antifungal activities than chitosan. Furthermore, quaternized chitosan derivatives with high molecular weight are shown to have even stronger antifungal activities than those with low molecular weight.     

Colorimetric determination of urinary adenosine using aptamer-modified gold nanoparticles

This paper describes a colorimetric sensing approach for the determination of adenosine triphosphate (ATP) using aptamer-modified gold nanoparticles (Apt-Au NPs). In the absence of the analytes, the color of the Apt-Au NPs solution changed from wine-red to purple as a result of salt-induced aggregation. Binding of the analytes to the Apt-Au NPs induced folding of the aptamers on the Au NP surfaces into four-stranded tetraplex structures (G-quartet) and/or an increase in charge density. As a result, the Apt-Au NPs solution was wine-red in color in the presence of the analytes under high salt conditions. For mixtures of ATP (20.0–100.0 nM), Apt-Au NPs (3.0 nM), 10.0% poly(ethylene glycol), 0.2 μM TOTO-3, 150.0 mM NaCl, 15.0 mM KCl, and 16.0 mM Tris–HCl (pH 7.4), a linear correlation (R² = 0.99) existed between the ratio of the extinctions of the Apt-Au NPs at 650 and 520 nm (Ex_650/520) and the concentration of ATP. The limit of detection for ATP was 10.0 nM. The practicality of this simple, sensitive, specific, and cost-effective approach was demonstrated through the determination of the concentration of adenosine in urine samples.     

Physical properties of fungal chitosan

Fungi are promising alternative sources of chitosan. This study evaluated the physical properties of fungal chitosan from Absidia coerulea (AF 93105), Mucor rouxii (Ag 92033), and Rhizopus oryzae (Ag 92033). FT-IR and X-ray diffraction of the extracted products showed typical chitosan peak distributions which confirmed the extracted products to be chitosan. All of their glucosamine contents and degrees of deacetylation (DD) were over 80%, not showing obvious differences respectively. However, differences had been observed in their molecular weight (M_w), ranging from 6.6  to 560 kDa. The results of this study demonstrated that different fungi could produce different M_w chitosan with high DD and high purity.     

Magnetic cell separation using nano-sized bacterial magnetic particles with reconstructed magnetosome membrane

Magnetic nanoparticles produced by magnetotactic bacterium, bacterial magnetic particles (BacMPs), covered with a lipid bilayer membrane (magnetosome membrane) can be used to separate specific target cells from heterogeneous mixtures because they are easily manipulated by magnets and it is easy to display functional proteins on their surface via genetic engineering. Despite possessing unique and valuable characteristics, the potential toxicity of BacMPs to the separated cells has not been characterized in detail. Here, a novel technique was developed for the reconstruction of magnetosome membrane of BacMPs expressing protein A (protein A-BacMPs) to reduce cytotoxicity and the newly developed nanomaterial was then used for magnetic cell separation. The development of the magnetosome membrane-reconstructed protein A-BacMP was based on the characteristics of the Mms13 anchor protein, which strongly binds to the magnetite surface of BacMPs. Treatment of protein A-BacMPs with detergents removed contaminating proteins but did not affect retention of Mms13-protein A fusion proteins. The particle surfaces were then reconstructed with phosphatidylcholine. The protein A-BacMPs containing reconstructed magnetosome membranes remained dispersible and retained the ability to immobilize antibody. In addition, they contained few membrane surface proteins and endotoxins, which were observed on non-treated protein A-BacMPs. Magnetic separation of monocytes and B-lymphocytes from the peripheral blood was achieved with high purity using magnetosome membrane-reconstructed protein A-BacMPs.     

变功率微波法制备壳聚糖絮凝剂的研究

研究了变功率下微波加热对甲壳素脱乙酰化反应和粘度的影响。结果表明:在4 80W下反应4min、然后在16 0W下反应6min的最佳功率组合下,可制得脱乙酰度77.3%、粘度4 6mPa·s的壳聚糖产品;与恒功率微波法相比,变功率微波法制备壳聚糖的脱乙酰度稍低,但粘度高出31% ,反应时间缩短三分之一,能耗降低6 0 %     

土壤中选育产壳聚糖酶菌株的研究

采用酶法降解壳聚糖具有反应条件易于控制、产物安全性高和环境污染少等独特的优越性。因此,筛选出高活力产壳聚糖酶菌株有着重要意义。该研究以不同地区采集土样分离出的1株细菌为出发菌株S,采用紫外线诱变（30W,20cm,5min）,经初筛和复筛及控温培养处理,获得了一株产壳聚糖酶较好的突变菌株,结果表明：所产酶活力达到3．47U/ml,酶活力提高近2倍,并具有较好的遗传稳定性,明显优于出发菌株,为发酵产壳聚糖酶的进一步研究提供了高产菌株。     

Thermal stabilization of trypsin with glycol chitosan

Glycol chitosan was evaluated as thermoprotectant additive for trypsin in aqueous solutions. Maximal stabilization was achieved by using a polymer/protein ratio of 2 (w/w). The catalytic properties of trypsin were not affected by the presence of the polysaccharide. The enzyme thermostability was increased from 49 °C to 93 °C in the presence of the additive. Trypsin was also 37-fold more stable against incubation at 55 °C and its activation free energy of thermal inactivation was increased by 9.9 kJ/mol when adding glycol chitosan.