添加壳聚糖的藻酸盐印模材料抗菌性能研究

目的:对添加壳聚糖的藻酸盐印模材料的抗菌性进行测试,为口腔抗茵印模材的研究奠定基础.方法:分别以不同的添加比将不同分子量和脱乙酰度的壳聚糖加入藻酸盐印模材料中,采用薄膜密着法分别测试添加抗菌成分后印模材料对大肠杆菌,金黄色葡萄球菌的抗茵活性.结果:壳聚糖分别以1%和1.4%的添加比添加到藻酸盐印模材料中,对大肠杆菌和金黄色葡萄球菌有最好的抗菌性.随着脱乙酰度的提高,抑菌率均可达到100%.结论:添加壳聚糖的藻酸盐印模材料具有良好的抗茵效果.     

不同分子量壳聚糖对五种常见菌的抑制作用研究

体外抑菌法研究了六种不同相对分子量的壳聚糖对金黄色葡萄球菌、大肠杆菌、绿脓杆菌、白色念珠菌、变形杆菌的抑菌活性,并对壳聚糖的抑菌机理做了探讨。     

不同分子量壳聚糖对五种常见茵的抑制作用研究

体外抑菌法研究了六种不同相对分子量的壳聚糖对金黄色葡萄球菌、大肠杆菌、绿脓杆菌、白色念珠菌、变形杆菌的抑菌活性,并对壳聚糖的抑菌机理做了探讨.     

低聚壳聚糖美拉德衍生物抑菌性能研究

本文研究了基于与葡萄糖、麦芽糖和木糖进行美拉德反应的低聚壳聚糖衍生物的抑菌性.测定低聚壳聚糖及其衍生物对大肠杆菌和金黄色葡萄球菌的抑制效果.结果显示:壳聚糖及其衍生物对金黄色葡萄球菌的抑制作用强于对大肠杆菌的抑制作用,且随着浓度增加,对两种菌的抑菌效果增强.大多数壳聚糖衍生物的抑菌效果优于壳聚糖本身,其中CG 1∶1 8 h(低聚壳聚糖的氨基与葡萄糖的羰基的物质量比为1∶1,反应8h)的抑菌效果最好,CM 1∶3 8 h(低聚壳聚糖的氨基与麦芽糖的羰基的物质量比为1∶3,反应8 h)抑菌性最差,这可能与参加反应的还原糖种类、反应物比例以及反应时间相关.     

壳聚糖吸附胆固醇的研究

血清中胆固醇水平高是冠心病等疾病的重要原因。在当前吸附法治疗高脂血症的推广应用中,所用吸附剂不是价格过于昂贵就是性能不稳定,很难应用于临床。本文试图以具有优良血液相容性和吸附性的壳聚糖用作胆固醇吸附剂。 通过 Ｈａｃｋｍａｎ法制备了壳聚精,并研磨成 ７５～１５０μｍ的粉末,加入血清中吸附,用酶氧化法测量吸附量。 实验中发现壳聚糖对胆固醇的吸附与壳聚糖脱乙酸化程度、分子量有密切关系,实验结果表明：随壳聚糖脱乙酸化度提高,壳聚糖对胆固醇吸附量也提高,当壳聚糖分子量为５３～５４万时,吸附量达到最大值,吸附量还跟壳聚糖形态有关,壳聚精粉末粒径越小越利于吸附。     

桑白皮中壳聚糖的分离与鉴定

首次报道了一种从桑白皮中分离壳聚糖的简便方便。经碱醇液高温处理 5h,壳聚糖收率为 7.2 % ,游离氨基为 2 9.6% ,脱乙酰度为 2 5% ,1%浓度壳聚糖的 1%醋酸溶液粘度为 1.52 MPa·s,平均分子量为 1.3× 10 3。     

纳米银胶/壳聚糖复合抗菌剂的制备及其在洗涤产品中抗菌性能

本文研究了纳米银胶/壳聚糖抗菌剂的制备及其形貌的表征分析,以大肠杆菌为代表菌株,研究了复合抗菌剂在洗涤产品中的抗菌效率及抗菌的稳定性,结果说明复合抗菌剂在洗涤产品中添加1.0%时,其抗菌效率达99%,经180 d长期分析,其抗菌活性仍保持95%左右。此外,复合抗菌剂对不同菌株的抗菌性能也均较强。     

九香虫血淋巴及其纯化蛋白抑菌活性的研究

对九香虫AsporgopuschinensisDallas血淋巴及其血淋巴蛋白质分离物的抗菌活性进行了研究,抗菌活性检测指示菌为大肠杆菌Escherichiacoli和金黄色葡萄球菌Staphilocalliesacereus。测定结果表明,九香虫血淋巴及其离心上清液都具有明显的抗菌活性。用凝胶过滤法从血淋巴蛋白分离提纯获得一种小分子肽,SDS PAGE电泳为单一带,分子量约为1～1 4 4kD。该小分子蛋白对大肠杆菌和金黄色葡萄球菌都有抑菌作用,与血淋巴对2种细菌的抗菌性一致,表明其是九香虫血淋巴中具抗菌作用的主要物质之一。     

AgNO3对大肠杆菌和金黄色葡萄球菌的抗菌作用及机制

以大肠杆菌和金黄色葡萄球菌为模式菌,对AgNO3的抗菌效果进行研究,并对其抗菌机制作初步探讨。AgNO3对大肠杆菌的抑制生长曲线表明:2.891 mg/L的AgNO3能够完全抑制106个/mL的大肠杆菌细胞生长,AgNO3使大肠杆菌和金黄色葡萄球菌的延滞期加长,并且浓度越高,延滞期越长。另外,AgNO3对大肠杆菌和金黄色葡萄球菌脱氢酶的活性有明显影响,随着AgNO3浓度的提高,脱氢酶的活性逐渐降低。AgNO3溶液作用于细菌后,细菌表面疏水性均有不同程度地下降,且浓度越大对其影响也越明显,大肠杆菌的下降程度要大于金黄色葡萄球菌。     

大肠杆菌生产的重组尿激酶的纯化及其特性

由大肠杆菌生产的重组尿激酶的高低分子量两种形式均已经重新折叠和提纯。对该蛋白质的低分子量形式作了比活性,氨基酸组成,氨基末端分析,羧基末端分析,胰蛋白酶图谱,抗体滴定,和色谱行为等特性描述。对高分子量形式作了比活性和色谱行为等特性描述。除缺少连接了天冬酰氨302碳水化合物外,在被试验的各个方面,重组尿激酶和天然尿激酶几乎完全相同。结果表明,由于大肠杆菌生产的可适当折叠,天然尿激 酶上连接的碳水化合物在酶的催化活性中不起作用。     

壳聚糖中胺基对其抑菌性能的影响及与DNA的作用

采用抑菌圈法研究了壳聚糖对大肠杆菌(E.coli)和金黄色葡萄球菌(St.aureus)的抑菌活性。利用壳聚糖的席夫碱反应,对壳聚糖的胺基进行保护后,研究了壳聚糖中胺基对其抑菌性能的影响。同时,运用紫外吸收光谱和电化学的方法,研究了壳聚糖与DNA的相互作用,提出了壳聚糖对E.coli和St.aureus的抑菌机理。研究结果表明,壳聚糖对E.coli和St.aureus具有很好的抑制作用,且抑菌活性与其胺基有关;壳聚糖能与细胞内带负电的核酸结合,使细胞正常DNA复制生理功能受到影响,抑制细菌的繁殖,从而达到抑菌的目的。     

Galactose dialdehyde: the forgotten candidate for a protein cross-linker?

Chitosan derivatives with quaternary ammonium salt, such as N,N,N-trimethyl chitosan, N-N-propyl-N,N-dimethyl chitosan and N-furfuryl-N,N-dimethyl chitosan were prepared using different 96% deacetylated chitosan of M(v) 2.14x10(5), 1.9x10(4), 7.8x10(3). Amino groups on chitosan react with aldehydes to from a Schiff base intermediate. Quaternized chitosan were obtained by reaction of a Schiff base with methyl iodide. The yields, degree of quaternization and water-solubility of quaternized chitosan were influenced by the molecular weight of the chitosan sample. The antibacterial activities of quaternized chitosan against Escherichia coli were explored by calculation of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) in water, 0.25 and 0.50% acetic acid medium. Results show the antibacterial activities of quaternized chitosan against E. coli is related to its molecular weight. Antibacterial activities of quaternized chitosan in acetic acid medium is stronger than that in water. Their antibacterial activities is increased as the concentration of acetic acid is increased. It was also found that the antibacterial activity of quaternized chitosan against E. coli is stronger than that of chitosan.     

Molecular weight and pH effects of aminoethyl modified chitosan on antibacterial activity in vitro

Aminoethyl modified chitosan derivatives (AEMCSs) with different molecular weight (Mw) were synthesized by grafting aminoethyl group on different molecular weight chitosans and chitooligosaccharide. FTIR, (1)H NMR, (13)C NMR, elemental analysis and potentiometric titration results showed that branched polyethylimine chitosan was synthesized. Clinical Laboratory Standard Institute (CLSI) protocols were used to determine MIC for Gram-negative strain of Escherichia coli under different pH. The antibacterial activity of the derivatives was significantly improved compared with original chitosans, with MIC values against E. coli varying from 4 to 64 μg/mL depending on different Mw and pH. High molecular weight seems to be in favor of stronger antibacterial activity. At pH 7.4, derivatives with Mw above 27 kDa exhibited equivalent antibacterial activity (16 μg/mL), while oligosaccharide chitosan derivative with lower Mw (~1.4 kDa) showed decreased MIC of 64 μg/mL. The effect of pH on antibacterial activity is more complicated. An optimal pH for HAEMCS was found around 6.5 to give MIC as low as 4 μg/mL, while higher or lower pH compromised the activity. Cell integrity assay and SEM images showed evident cell disruption, indicating membrane disruption may be one possible mechanism for antibacterial activity.     

Antibacterial characteristics and activity of acid-soluble chitosan

The antibacterial activity of chitosan was investigated by assessing the mortality rates of Escherichia coli and Staphylococcus aureus based on the extent of damaged or missing cell walls and the degree of leakage of enzymes and nucleotides from different cellular locations. Chitosan was found to react with both the cell wall and the cell membrane, but not simultaneously, indicating that the inactivation of E. coli by chitosan occurs via a two-step sequential mechanism: an initial separation of the cell wall from its cell membrane, followed by destruction of the cell membrane. The similarity between the antibacterial profiles and patterns of chitosan and those of two control substances, polymyxin and EDTA, verified this mechanism. The antibacterial activity of chitosan could be altered by blocking the amino functionality through coupling of the chitosan to active agarose derivatives. These results verify the status of chitosan as a natural bactericide.     

Antibacterial effects of water-soluble low-molecular-weight chitosans on different microorganisms

Low-molecular-weight chitosans with a viscosity-average molecular weight (Mv) of 5 to 27 kDa and equal degree of deacetylation (DD, 85%) were highly active against Pseudomonas aureofaciens, Enterobacter agglomerans, Bacillus subtilis, and Bifidobacterium bifidum 791, causing death of 80 to 100% of cells. An exception to this tendency was Escherichia coli, for which the rate of cell death, induced by the 5-kDa chitosan, was 38%. The antibacterial effect was manifested as early as 10 min after incubation of 12-kDa chitosan with B. subtilis or E. coli cells. Candida krusei was almost insensitive to the above crab chitosans. However, Candida krusei was highly sensitive to chitosans with Mv 5, 6, 12, 15.7, and 27 kDa: the minimum inhibitory concentration (MIC) varied from 0.06 to 0.005%. Chitosans with M, 5, 12, and 15.7 kDa exerted an antibacterial effect on Staphylococcus aureus. Chitosans with Mv 5, 15.7, and 27 kDa had no effect on Bifidobacterium bifidum ATCC 14893. The antibacterial effect of the 4-kDa chitosan on E. coli and B. bifidum 791 increased with DD in the range 55-85%.     

Effect of abiotic factors on the antibacterial activity of chitosan against waterborne pathogens

To assess the adaptability of chitosan (from agricultural waste) as a natural disinfectant, its antibacterial activity against bacteria associated with waterborne diseases was investigated by varying such abiotic conditions, as pH and ionic strength and by adding different amounts of acid solvent, metal ions, and EDTA. Two major waterborne pathogens, Escherichia coli and Staphylococcus aureus, were examined. Results showed that organic acids with low carbon number were better solvents for chitosan than were inorganic acids. The effect of pH below 6 on the antibacterial activity of chitosan was significant. The antibacterial activity of chitosan increased with ionic strength but decreased with the addition of metal ions. The addition of Zn(2+) ions inhibited the antibacterial activity of chitosan the most, while the addition of Mg(2+) ions inhibited the antibacterial activity of chitosan the least. This was due to the chelating capacity of chitosan toward metal ions. The antibacterial activity of chitosan against E. coli was enhanced by EDTA. However, the antibacterial activity of chitosan against S. aureus was partially suppressed by EDTA. The antibacterial activity of chitosan was also dependent on its charges and solubility. The antibacterial mechanism of chitosan has currently been hypothesized as being related to surface interference. The results show that the chitosan is a potential bactericide under various environmental conditions.     

Separation and purification of a potent bactericidal/permeability-increasing protein and a closely associated phospholipase A2 from rabbit polymorphonuclear leukocytes. Observations on their relationship.

Two antibacterial proteins from rabbit polymorphonuclear leukocytes, a potent bactericidal cationic protein that increases the envelope permeability of susceptible gram-negative bacteria and a phospholipase A2, have been purified to near homogeneity by ion exchange, gel filtration, and hydrophobic interaction chromatography. The apparently noncatalytic bactericidal/permeability-increasing protein has an approximate molecular weight of 50,000 and is isoelectric at pH 9.5 to 10.0. The molecular properties, including amino acid composition, and the antibacterial potency and specificity of this rabbit leukocyte protein and of the bactericidal/permeability-increasing protein from human granulocytes that we have recently purified (J. Biol. Chem. 253, 2664-2672, 1978) are closely similar. Both proteins kill several strains of Escherichia coli and Salmonella typhimurium. Rough strains are more sensitive than smooth strains. All gram-positive bacterial species tested are insensitive to high concentrations of either rabbit or human protein. The phospholipase A2, purified by hydrophobic interaction chromatography on phenyl-Sepharose, ran as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 14,000 and had a specific enzymatic activity comparable to that of purified phospholipases A2 from other sources. Separation of the phospholipase A2 from the bactericidal/permeability-increasing protein has no noticeable effect on the bactericidal and permeability-increasing activities of the purified bactericidal protein, but removes the ability of the phospholipase A2 to hydrolyze the phospholipids of intact Escherichia coli. Upon recombination of the phospholipase A2 with the bactericidal/permeability-increasing protein, the phospholipase A2 regains its activity toward the phospholipids of intact E. coli suggesting that these two antibacterial leukocyte proteins act in concert.     

Synthesis and antimicrobial activity of a water-soluble chitosan derivative with a fiber-reactive group

A novel fiber-reactive chitosan derivative was synthesized in two steps from a chitosan of low molecular weight and low degree of acetylation. First, a water-soluble chitosan derivative, N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan chloride (HTCC), was prepared by introducing quaternary ammonium salt groups on the amino groups of chitosan. This derivative was further modified by introducing functional (acrylamidomethyl) groups, which can form covalent bonds with cellulose under alkaline conditions, on the primary alcohol groups (C-6) of the chitosan backbone. The fiber-reactive chitosan derivative, O-acrylamidomethyl-HTCC (NMA-HTCC), showed complete bacterial reduction within 20 min at the concentration of 10ppm, when contacted with Staphylococcus aureus and Escherichia coli (1.5-2.5 x 10(5) colony forming units per milliliter [CFU/mL]).     

Structure and antimicrobial activities of benzoyl phenyl-thiosemicarbazone-chitosans

Previously, we had prepared acetyl phenyl-thiosemicarbazone derivatives of chitosan, and their antimicrobial activities were analyzed. The purpose of the present study was to further assess the relationship between the structure and antimicrobial activities of benzoyl phenyl-thiosemicarbazone-chitosan. Ten new benzoyl phenyl-thiosemicarbazone-chitosans were prepared and their structures were characterized by FT-IR and elemental analysis. The antimicrobial experiment against four species of bacteria and four crop-threatening pathogenic fungi were conducted based on the derivatives of chitosan with different molecular weight at different concentrations. The results indicated that the antimicrobial activities of benzoyl phenyl-thiosemicarbazone derivatives are much better than that of pure CS. The value of the minimum inhibition concentration (MIC) and the minimum bactericidal concentration (MBC) of the derivatives against Escherichia coli was 7.03 and 225 μg mL(-1) respectively. All of the derivatives had significant inhibiting effect on the investigated fungi in the concentration of 50-500 μg mL(-1), and the maximum inhibitory index was 94.74%. These results indicate that the derivatives have potential ability used as antibacterial reagent in agricultural field.     

Factors affecting the entry of antibiotics into Escherichia coli

Factors affecting the entry into Escherichia coli of diverse antibacterial agents, especially beta-lactams were investigated. Agents of greater than a critical molecular weight (approximately 600 Daltons) penetrated extremely poorly. However, there was little correlation between penetrative ability and molecular weight for substances below the critical size. Within classes of related antibiotics (e.g. cephalosporins) penetrative ability was highly dependent on hydrophobicity. The relationship was parabolic rather than linear in nature. The proposal that the envelope of E. coli preferentially excludes hydrophobic molecules is to some extent an artefact arising from pre-selection of the agents used. For unrelated antibiotics hydrophobic nature was a poor guide to penetrative ability. A rather empirical property, diffusion ability through agar, was found to show good inverse correlation with penetrative ability for many unrelated antibiotics.