几丁聚糖在硅橡胶表面作涂层的实验研究

几丁聚糖具有良好的生物相容性和抗菌性,作为生物涂层已经引起了广泛的注意。研究了基体的不同表面处理方法、浸涂次数和几丁聚糖溶液浓度对涂层的表面形貌、结合强度等性能的影响,结果显示,几丁聚糖溶液浓度和硅橡胶表面粗糙度都存在一个最佳取值范围;增加浸涂次数可以改善涂层光洁度,但是对涂层附着力贡献不大;硅橡胶经紫外照射后可以改善几丁聚糖在其上的成膜性能。     

核酸适配子表面改性医用不锈钢及其内皮祖细胞捕获性能研究

本论文以多巴胺和聚乙烯亚胺为反应组分,在医用不锈钢表面制备了Dopa-PEI涂层,并在该涂层进一步固定核酸适配子,以构建出具有捕获内皮祖细胞(EPCs)的功能化涂层。衰减全反射傅里叶红外光谱结果表明多巴胺和PEI通过迈克尔加成和西弗碱反应在医用不锈钢表面形成了交联涂层。石英晶体微天平(QCM-D)检测结果显示表面固定的核酸适配子密度可达到298.4 ng/cm2;体外内皮祖细胞的动态捕获实验表明表面固定核酸适配子的样品在动态条件下能有效地捕获内皮祖细胞。本论文的研究结果为具有内皮祖细胞捕获功能的血管支架表面构建提供了有效的改性手段。     

几丁聚糖在组织工程中的应用

支架材料作为组织工程的生物学植入替代物,对细胞移植与引导新组织生长有重要的作用。几丁聚糖可制成无毒性,无刺激性,生物相容性和生物可降解性良好的生物医用材料,在人工皮肤,骨修复材料,手术缝线等方面已广泛应用。本文分析了纯几丁聚糖支架结构和它与其他天然或合成材料复合的支架结构的物理、化学性质及其独特的生物学功能,同时还进一步介绍了其应用的范例并探讨了发展前景。     

医用几丁聚糖在临床医学中的应用

医用几丁聚糖是从虾/蟹壳中藉生物提取的几丁质(chi tin)经脱乙酰基后为几丁糖(chito san),再经深加工达到医用级水平的天然生物材料,是继纤维素后的世上第二大天然资源,据报导有100万～1000万亿吨之多。目前仅利用了数万吨,其中大约25％用于医学领域。早在1811年,法国布Brac on not发现了蘑菇中含有几丁质,当时称之为Fung in,1823年法国科学家Odier在昆虫表面坚硬的皮质中发现了这种物质,并用希腊语chitin将其命名,因此沿用迄今。尽管发现是如此之早,但对其研究却十分缓慢。一百多年后,1977年4月第一届几丁     

生物陶瓷技术的现状与发展趋势

生物陶瓷主要应用于生物硬组织医用材料,其基础研究从1965年开始,临床研究从1975年开始.传统的生物硬组织医用材料有体骨,动物内,后来发展到采用不锈钢和塑料.但这些材料在生物体中使用效果不理想：不锈钢存在溶析、腐蚀和疲劳问题,塑料存在稳定性差和强度低的问题。1990年代初,国际上兴起了人工骨研究,即将生物陶瓷用作医用复合材料,应用于人体生物体的修复,制做人工关节、人工骨、人工牙根、听觉小骨、中耳引流管等。生物陶瓷能模仿人体骨头的成分、强度,不仅具有不锈钢塑料所具有的特性,     

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。     

几丁聚糖对双歧杆菌体外生长的影响

目的观察几丁聚糖对双歧杆菌是否有增菌作用。方法应用分光光度比色法分析几丁聚糖对双歧杆菌体外生长作用的影响,并与中药黄芪对该菌的作用进行比较。结果与对照组比较,几丁聚糖和黄芪浓度分别为2.5 mg/mL和62.5 mg/mL时,对双歧杆菌有明显的增殖作用（P〈0.05）。比较两种药物在该浓度时对双歧杆菌的生长作用,虽然黄芪的增殖作用高于几丁聚糖,但差异无统计学意义（P〉0.05）。结论 2.5 mg/mL剂量的几丁聚糖体外能够促进双歧杆菌的生长。     

几丁聚糖和透明质酸钠对血管内皮细胞增殖的影响

目的：比较几丁聚糖和透明质酸钠对血管内皮细胞增殖的影响。方法：用含不同浓度的几丁聚糖和透明质酸钠的培养液对血管内皮细胞（EV304）进行培养,以四唑盐比色法测细胞增殖,并用流式细胞仪测定细胞周期。结果：几丁聚糖在≥0.1mg/ml时促进血管内皮细胞的增殖,透明质酸钠对血管内皮细胞的增殖有抑制作用,几丁聚糖可使细胞周期中G1期比例下降,而透明质酸钠使细胞周期中G1期比例上升。结论：几丁聚糖促进血管内皮细胞的增殖,而透明质酸钠对血管内皮细胞的增殖有抑制作用。     

Cu 型医用抗菌不锈钢在大鼠体内抗细菌感染研究

目的:比较普通304医用不锈钢和304-Cu型医用抗菌不锈钢的体内抗细菌感染性能。方法:将两种不锈钢片涂布浓度为1×107cfu/mL的金黄色葡萄球菌培养24 h,植入SD大鼠胫腓骨肌袋内,继续饲养并在术前及术后第1、4、7、14天进行大体观察、植入部位细菌培养、白细胞计数、组织学观察等检测。结果:普通304不锈钢组术后中度化脓,检测到较多细菌,白细胞增多且有大量的炎症细胞出现;而304-Cu型抗菌不锈钢术后只有轻微化脓,检测到的细菌较少,白细胞数稍有增多但无统计学差异,炎症细胞少,感染程度轻。结论:与医用304不锈钢相比,304-Cu型抗菌不锈钢有较好的抗细菌性能,有一定的抗感染作用。     

几丁聚糖促进人脐静脉内皮细胞的生长及相关蛋白的表达

目的：研究几丁聚糖对体外培养的人脐静脉内皮细胞生长的影响及相关作用机制。方法：用不同质量浓度的几丁聚糖和雷帕霉素培养液培养内皮细胞48h,以四唑盐比色法测细胞增殖。免疫组化测c-Myc,Bcl-2和Bax蛋白的表达。结果：随着几丁聚糖质量浓度≥0．01mg／ml的增加,内皮细胞数增多（P〈0.05）,同时Bax的表达降低。结论：几丁聚糖通过下调Bax的表达抑制内皮细胞的凋亡,起到增殖的效果。     

含铜抗菌不锈钢的抗菌性能研究

对铁素体和奥氏体2种含铜抗菌不锈钢的抗菌性能进行了考察.采用覆膜法检测抗菌率,用透射电镜观察与铁素体抗菌不锈钢作用后的大肠埃希菌细胞形态.2种抗菌不锈钢材料对供试的 17 株常见菌,除产气肠杆菌外均显示较强的抗菌性能,抗菌谱广;铁素体和奥氏体对1×107 cfu/mL及以下浓度的大肠埃希菌在 24 h内杀灭率达到99%;铁素体和奥氏体分别在作用 3 h和 9 h时可将1×107 cfu/mL的大肠埃希菌全部杀灭;打磨次数和环境温度的变化不影响2种抗菌不锈钢的杀菌率;透射电镜结果显示,与抗菌不锈钢作用后的大肠埃希菌菌体结构松散,细胞壁和细胞膜破裂,有内容物漏出.铁素体和奥氏体抗菌不锈钢均具优良的抗菌性能,抗菌谱广,与其作用后的细菌菌体破裂,有内容物溶出,最终致菌死亡.     

Preparation and characterization of chitosan-based nanoparticles

The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on chitosan for biomedical applications. Natural di- and tricarboxylic acids were used for intramolecular cross-linking of the chitosan linear chains. The condensation reaction of carboxylic groups and pendant amino groups of chitosan was performed by using water-soluble carbodiimide. This method allows the formation of polycations, polyanions, and polyampholyte nanoparticles. The prepared nanosystems were stable in aqueous media at low pH, neutral, and mild alkaline conditions. The structure of products was determined by NMR spectroscopy, and the particle size was identified by laser light scattering (DLS) and transmission electron microscopy (TEM) measurements. It was found that particle size depends on the pH, but at a given pH, it was independent of the ratio of cross-linking and the cross-linking agent. Particle size measured by TEM varied in the range 60-280 nm. In the swollen state, the average size of the particles measured by DLS was in the range 270-370 nm depending on the pH. The biodegradable cross-linked chitosan nanoparticles, as solutions or dispersions in aqueous media, might be useful for various biomedical applications.     

The synthesis of chitosan-based silver nanoparticles and their antibacterial activity

Chitosan-based silver nanoparticles were synthesized by reducing silver nitrate salts with nontoxic and biodegradable chitosan. The silver nanoparticles thus obtained showed highly potent antibacterial activity toward both Gram-positive and Gram-negative bacteria, comparable with the highly active precursor silver salts. Silver-impregnated chitosan films were formed from the starting materials composed of silver nitrate and chitosan via thermal treatment. Compared with pure chitosan films, chitosan films with silver showed both fast and long-lasting antibacterial effectiveness against Escherichia coli. The silver antibacterial materials prepared in our present system are promising candidates for a wide range of biomedical and general applications.     

Novel chitin and chitosan nanofibers in biomedical applications

Chitin and its deacetylated derivative, chitosan, are non-toxic, antibacterial, biodegradable and biocompatible biopolymers. Due to these properties, they are widely used for biomedical applications such as tissue engineering scaffolds, drug delivery, wound dressings, separation membranes and antibacterial coatings, stent coatings, and sensors. In the recent years, electrospinning has been found to be a novel technique to produce chitin and chitosan nanofibers. These nanofibers find novel applications in biomedical fields due to their high surface area and porosity. This article reviews the recent reports on the preparation, properties and biomedical applications of chitin and chitosan based nanofibers in detail.     

Impact of biological factors on the ennoblement of stainless steel in Baltic seawater

Open circuit potentials of stainless steels increased when immersed in the Baltic Sea. The ennoblement potential was +200 mV_sce in 40 to 50 days when sea water temperature was below 52°C and +300–400 mV_sce within <40 days at around 102°C. Ennoblement occurred in a laboratory ecosystem at 232°C in 20 to 30 days, and at 262°C in <20 days, but no ennoblement occurred at A322°C within 40 days. By the time the ennoblement was complete, compact microcolonies covered 1–10% of the steel surface. Nutrient enrichment of Baltic Sea water by twofold above the natural levels increased microbial growth but attenuated open circuit potential increase of the stainless steels. Exposure of the ennobled stainless steels to similar levels of nutrients did not reverse the already developed open circuit potentials. Attenuation of the ennobling response of the stainless steels by increases of temperature and eutrophication suggests a role for microorganisms which is crucial for the electrochemical behaviour of steels in brackish Baltic Sea water. Journal of Industrial Microbiology & Biotechnology (2000) 24, 410–420. Received 02 November 1999/ Accepted in revised form 24 March 2000     

Bactericidal Activity of Copper and Niobium–Alloyed Austenitic Stainless Steel

Biofouling and microbiologically influenced corrosion are processes of material deterioration that originate from the attachment of microorganisms as quickly as the material is immersed in a nonsterile environment. Stainless steels, despite their wide use in different industries and as appliances and implant materials, do not possess inherent antimicrobial properties. Changes in hygiene legislation and increased public awareness of product quality makes it necessary to devise control methods that inhibit biofilm formation or to act at an early stage of the biofouling process and provide the release of antimicrobial compounds on a sustainable basis and at effective level. These antibacterial stainless steels may find a wide range of applications in fields, such as kitchen appliances, medical equipment, home electronics, and tools and hardware. The purpose of this study was to obtain antibacterial stainless steel and thus mitigate the microbial colonization and bacterial infection. Copper is known as an antibacterial agent; in contrast, niobium has been demonstrated to improve the antimicrobial effect of copper by stimulating the formation of precipitated copper particles and its distribution in the matrix of the stainless steel. Thus, we obtained slides of 3.8% copper and 0.1% niobium alloyed stainless steel; subjected them to three different heat treatment protocols (550°C, 700°C, and 800°C for 100, 200, 300, and 400 hours); and determined their antimicrobial activities by using different initial bacterial cell densities and suspending solutions to apply the bacteria to the stainless steels. The bacterial strain used in these experiments was Escherichia coli CCM 4517. The best antimicrobial effects were observed in the slides of stainless steel treated at 700°C and 800°C using an initial cell density of approximately 10⁵ cells ml⁻¹ and phosphate-buffered saline as the solution in which the bacteria came into contact with copper and niobium–containing steel.     

Synthesis and characterization of sugar-bearing chitosan derivatives: aqueous solubility and biodegradability

The extended use of chitosan in biomedical fields has been limited by its insoluble nature in a biological solution. To endow the water solubility in a broad range of pH, chitosan derivatives were prepared by the covalent attachment of a hydrophilic sugar moiety, gluconic acid, through the formation of an amide bond. These sugar-bearing chitosans (SBCs) were further modified by the N-acetylation in an alcoholic aqueous solution. Thereafter, the effect of the gluconyl group and the degree of N-acetylation (DA) on the water solubility at different pHs and on the biodegradability of chitosan were investigated. The SBCs showed the water solubility in a broader range of pH than chitosan, whereas they were still insoluble at neutral and alkali pH. The N-acetylation of SBCs significantly affected the water solubility, for example, the SBCs with the DA, ranging from 29% to 63%, were soluble in the whole range of pH. This might result from the improved hydrophilicity by the gluconyl group, accompanied by the role of the N-acetyl group that disturbed the hydrogen bonding between amino groups of chitosan. From the biodegradation tests, determined by the decrease in the viscosity of a polymer solution exposed to lysozyme, it was evident that the gluconyl group attached to chitosan improved the biodegradability. Thus, it was possible to control the biodegradability of chitosan by adjusting the amounts of gluconyl and N-acetyl groups in the chitosan backbone. The N-acetylated SBCs, soluble in the broad range of pH, might be useful for various biomedical applications.     

Chitosan-induced restructuration of a mica-supported phospholipid bilayer: an atomic force microscopy study

Chitosan has emerged as a promising material for biomedical applications. However, the effect of chitosan adsorption on the structure of model biomembrane is not known. In this study, atomic force microscopy (AFM) is employed to investigate the interaction between chitosan and mica-supported dipalmitoylphosphocholine (DPPC) bilayer. First, in situ AFM measurement indicates that nucleation of chitosan occurs around the membrane defects at the initial stage of chitosan incubation. Eventually, DPPC-chitosan binding and chitosan intermolecular association lead to chitosan aggregation on the membrane surface which is quantified by average height measurement and RMS roughness analysis. Lateral force microscopy (LFM) confirms that the adsorbed chitosan has distinct material properties. Furthermore, the trend of surface pressure-area isotherms supports the condensation of DPPC monolayer induced by chitosan in the aqueous subphase. Surface coverage and surface roughness analysis show that the extent of chitosan aggregation on the supported membrane is affected by the incubation time during long-term chitosan incubation.