新型纳米银体外广谱抗菌作用及机制

目的探讨新型纳米银体外对临床感染常见细菌的广谱抗菌作用及机制。方法选择临床常见的金黄色葡萄球菌、大肠埃希菌、肺炎克雷伯菌、鲍曼不动杆菌和铜绿假单胞菌为研究对象,采用平板涂布法检测新型纳米银的广谱抗菌作用,利用透射电镜观察细菌呼吸链脱氢酶活性和细菌细胞膜的渗漏性改变,探讨新型纳米银的抗菌作用机制。结果新型纳米银浓度超过0.05μg/mL对临床感染常见的5种细菌具有明显的抑制作用;浓度5μg/mL的新型纳米银体外作用临床感染常见细菌5min,可100%抑制细菌生长。电镜观察新型纳米银可吸附在金黄色葡萄球菌和大肠埃希菌的菌体表面,改变了细菌形态结构。新型纳米银可明显抑制金黄色葡萄球菌与大肠埃希菌的呼吸链脱氢酶活性;较高浓度的新型纳米银可破坏金黄色葡萄球菌与大肠埃希菌的细胞膜,导致细菌胞浆内容物外漏。结论新型纳米银对临床感染常见细菌具有广谱高效的抗菌作用,其作用机制可能与新型纳米银吸附在细菌表面,抑制细菌表面生物大分子功能或活性有关,研究结果为新型纳米银抗菌作用的深入研究及临床应用提供了实验依据。     

新型纳米银胶体溶液体外对耐甲氧西林金黄色葡萄球菌的抑制作用及机制

目的探讨新型纳米银胶体溶液体外对耐甲氧西林金黄色葡萄球菌(MRSA)的抑制作用及机制。方法以MRSA为研究对象,采用涂布法检测新型纳米银胶体溶液的杀菌作用,同时分析体外不同作用时间、剂量及因素对新型纳米银胶体溶液杀菌效果的影响。采用比色法检测细菌呼吸链脱氢酶活性,采用透射电镜观察其对MRSA菌体形态的影响。结果 0.05μg/mL新型纳米银胶体溶液对MRSA具有明显杀菌作用(抑菌率97.0%)。5μg/mL新型纳米银胶体溶液对MRSA作用5、15、30、60 min时均有明显杀菌作用(抑菌率均≥98.0%)。血清白蛋白对新型纳米银胶体溶液体外杀菌效果影响显著。新型纳米银胶体溶液能有效抑制MRSA呼吸链脱氢酶活性,对MRSA菌体形态破坏明显。结论新型纳米银胶体溶液体外对MRSA具有高效、多靶位抑制作用,可作为抗耐药菌治疗的新途径。     

胶体纳米银对产超广谱β-内酰胺酶肺炎克雷伯菌的抑制作用

目的探讨胶体纳米银对产超广谱β-内酰胺酶(ESBLs)肺炎克雷伯菌的抑制作用。方法以产ESBLs肺炎克雷伯菌为研究对象,采用涂布法检测杀菌作用,肉汤微量稀释法测量最低抑菌浓度(MIC),电镜法观察胶体纳米银对产ESBLs肺炎克雷伯菌的作用机理。结果≥0.5μg/mL的胶体纳米银对产ESBLs的肺炎克雷伯菌具有100%杀菌作用;≥0.05μg/mL的胶体纳米银对产ESBLs的肺炎克雷伯菌也具有明显的杀菌作用;5μg/mL胶体纳米银对产ESBLs肺炎克雷伯菌5、15、30和60 min均有明显的杀菌作用;胶体纳米银对产ESBLs肺炎克雷伯菌的MIC为3.125μg/mL;不同因素对胶体纳米银的杀菌作用,蛋白因素影响显著(P0.05);胶体纳米银对产ESBLs肺炎克雷伯菌的形态学有明显影响。结论胶体纳米银对产ESBLs肺炎克雷伯菌具有明显的抑制作用,这些结果将为胶体纳米银的临床应用提供了实验依据。     

纳米银体外抗腺病毒作用初步研究

目的探讨纳米银(silver nanoparticles,silver-nps)在体外对腺病毒3型(Adenovirus type 3,ADV3)的抑制作用。方法运用细胞培养技术、MTT测值法、CPE和免疫荧光观察法,分析纳米银对ADV3感染HeLa细胞的预防作用、直接灭活作用以及对ADV3子代病毒体生成的抑制作用。结果纳米银能明显杀伤ADV3,且呈剂量依赖性;纳米银在HeLa细胞上最大无毒浓度(TC0)为52.48μg/ml;ADV3在HeLa细胞上的组织半数感染量(TCID50)为10-2.74/100μl;最大无毒剂量范围内,50、25、12.5、6.25和3.125μg/ml的纳米银分别与100 TCID50ADV3等体积混合,细胞存活率分别为(95.38±2.60)%、(60.51±9.42)%、(57.99±8.72)%、(41.35±3.91)%和(37.88±3.75)%,而100 TCID50ADV3感染HeLa细胞后,测得细胞存活率为(31.92±8.98)%,二者相比差异有统计学意义(P0.05);免疫荧光结果显示,与纯病毒组形成的强特异性荧光相比,纳米银在ADV3吸附细胞后加入、吸附前预处理HeLa细胞和纳米银同ADV3同时作用三种途径特异性荧光都很少见,说明纳米银在不同途径下对ADV3均有抑制作用。结论纳米银对腺病毒3型具有明显的抑制作用。     

纳米银的抗菌机制及临床应用研究

纳米银因具备抗菌谱广、效果好、安全性高等特性,其医疗制品在临床治疗方面应用广泛。现普遍认为纳米银可通过释放银离子(Ag+)和诱导活性氧自由基的表达等方式达到杀菌目的,但其发挥抗菌作用的效果受到表面正电荷和粒子直径等因素影响。本文就纳米银的抗菌机制及临床实践应用进行综述,对现有的各种抗菌材料进行分类,重点探讨纳米银对金黄色葡萄球菌、大肠埃希菌、白假丝酵母菌和铜绿假单胞菌的杀菌和抑菌原理,以及其在抗菌过程中的影响因素,并阐述了纳米银及其复合材料在临床实践中的应用,以期为纳米银抗菌应用方面的后续研究提供一些参考。     

胶体纳米银对白假丝酵母菌的抑制作用

目的 探讨胶体纳米银对白假丝酵母菌的抑制作用。方法 以白假丝酵母菌为研究对象,采用倍比稀释及涂布法,检测胶体纳米银对白假丝酵母菌的抑制作用及影响因素。结果 化学纳米银及物理纳米银对白假丝酵母菌的最小抑菌浓度及最小杀菌浓度相同,分别为3.13 μg/mL和6.25 μg/mL。12.50 μg/mL的化学纳米银及物理纳米银可在5 min内完全杀死白假丝酵母菌。胶体纳米银的抑菌作用受到杀菌环境的影响,特别氯离子对胶体纳米银的杀菌作用有明显的影响。结论 胶体纳米银对白假丝酵母菌具有明显的抑菌作用,其抑制作用易受到氯离子及蛋白质的的影响。     

纳米银-活性炭纤维敷料的体外抗菌实验研究

目的：观察比较纳米银-活性炭纤维敷料、纳米银敷料、碳纤维敷料和普通敷料对大肠杆菌、金黄色葡萄球菌和绿脓杆菌的抑菌效果,为临床创面合理应用敷料提供理论依据。方法：1）、抑菌圈法将敷料剪成直径为10mm的圆片,灭菌后贴于接菌的培养皿上,置37℃电热恒温培养箱培养16～24小时,游标卡尺测量抑菌圈大小。2）、振荡烧瓶实验称取被剪成10mm×10mm大小的敷料样品0.75g,灭菌后加于含70mL PBS和5mL浓度为1×104cfu/mL菌悬液的250 mL烧瓶,封口固定于振荡器上以300r/h分别振荡2min和1h,各取20μL样液作为振荡前和振荡后,均匀涂于MH培养皿,37℃电热恒温培养箱孵育16～24小时后计数,测定抑菌率。结果：与其他三组敷料相比,纳米银-活性炭纤维敷料的抑菌圈和抑菌率最大（P〈0.05）。结论：纳米银-活性炭纤维敷料具有较强的广谱抗菌作用,是目前临床上较为理想的创面抗感染敷料。     

纳米银抑制铜绿微囊藻的研究

目的:探讨不同浓度的纳米银对铜绿微囊藻的影响。方法:采用血球计数板计数和电子扫描显微镜研究纳米银对铜绿微囊藻生长和形态的影响。结果:当纳米银的浓度达到1.965 mg/L时,对铜绿微囊藻细胞的生长繁殖和叶绿素a的合成有抑制作用;当纳米银的浓度大于或等于9.825 mg/L时完全抑制叶绿素a的合成,但藻细胞依然能够存活。随着纳米银浓度的升高,对铜绿微囊藻的抑制作用增强。在扫描电镜下,可以清晰地看到纳米银与铜绿微囊藻的相互作用,纳米银结合在铜绿微囊藻的细胞壁上,引起细胞形变或裂解。结论:实验结果表明纳米银对铜绿微囊藻叶绿素a合成有较强的抑制作用,对细胞的生长繁殖的抑制相对较弱。     

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。     

纳米银在水-沉积物中的迁移机制研究

为研究纳米银(Ag NPs)在水体中的迁移、水-沉积物中的分配及转化机制,采用武汉东湖湖水及沉积物开展模拟实验,以硝酸银(Ag NO3)为参照,研究了Ag NPs和聚乙烯吡咯烷酮包裹纳米银[Poly(vinylpyrrolidone)-coated silver nanoparticles(PVP-Ag NPs)]在上覆水中的沉降、在沉积物中的迁移和形态分布、以及扰动释放过程。结果表明,上覆水银初始浓度均为75 mg/L的Ag NO3、Ag NPs及PVP-Ag NPs在120h后分别为0.086、0.957和2.770 mg/L,显示纳米银和硝酸银进入水体后120h内大部分沉入沉积物中,且经过包裹的纳米银比未包裹的纳米银在水中停留时间稍长;60d后三种银均主要分布在表层沉积物中,Ag NO3体系银含量随深度的增加而逐渐降低,Ag NPs和PVP-Ag NPs体系银在2 cm以上随深度的增加而增高,随后逐渐降低,表明纳米银比硝酸银具有更强的迁移能力。此外,PVP-Ag NPs在2—3 cm层中的银含量占总量的24.6%,而Ag NPs在同一层中含量仅为2.6%,说明前者的迁移能力更强。在沉积物中,硫化物和有机物是银的主要结合相。释放实验结果表明,沉积物中纳米银的释放量远小于硝酸银的释放量,表明纳米银一旦与沉积物结合就难以再次释放。以上实验结果为评价纳米银的生态安全提供了科学依据。     

Interaction of silver nanoparticles with catechol O-methyltransferase: Spectroscopic and simulation analyses

Catechol O-methyltransferase, an enzyme involved in the metabolism of catechol containing compounds, catalyzes the transfer of a methyl group between S-adenosylmethionine and the hydroxyl groups of the catechol. Furthermore it is considered a potential drug target for Parkinson’s disease as it metabolizes the drug levodopa. Consequently inhibitors of the enzyme would increase levels of levodopa. In this study, absorption, fluorescence and infrared spectroscopy as well as computational simulation studies investigated human soluble catechol O-methyltransferase interaction with silver nanoparticles. The nanoparticles form a corona with the enzyme and quenches the fluorescence of Trp143. This amino acid maintains the correct structural orientation for the catechol ring during catalysis through a static mechanism supported by a non-fluorescent fluorophore–nanoparticle complex. The enzyme has one binding site for AgNPs in a thermodynamically spontaneous binding driven by electrostatic interactions as confirmed by negative ΔG and ΔH and positive ΔS values. Fourier transform infrared spectroscopy within the amide I region of the enzyme indicated that the interaction causes relaxation of its β?structures, while simulation studies indicated the involvement of six polar amino acids. These findings suggest AgNPs influence the catalytic activity of catechol O-methyltransferase, and therefore have potential in controlling the activity of the enzyme.     

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.     

The effect of gold and silver nanoparticles,chitosan and their combinations on bacterial biofilms of food-borne pathogens

Abstract

The antimicrobial activity of gold and silver nanoparticles (AuNPs, AgNPs), chitosan (CS) and their combinations was established by determining the minimum inhibitory concentration for planktonic (MICPC₈₀) and biofilm growth (MICBC₈₀), for biofilm formation (MICBF₈₀), metabolic activity (MICBM₈₀) and reduction (MICBR₈₀), and for the metabolic activity of preformed biofilm (MICMPB₈₀). Biofilms were quantified in microtitre plates by crystal violet staining and metabolic activity was evaluated by the MTT assay. Chitosan effectively suppressed biofilm formation (0.31–5?mg ml^?1) in all the tested strains, except Salmonella enterica Infantis (0.16–2.5?mg ml^?1) where CS and its combination with AgNPs induced biofilm formation. Nanoparticles inhibited biofilm growth only when the highest concentrations were used. Even though AuNPs, AgNPs and CS were not able to remove biofilm mass, they reduced its metabolic activity by at least 80%. The combinations of nanoparticles with CS did not show any significant positive synergistic effect on the tested target properties.     

Cytogenetic effects of silver and gold nanoparticles on Allium cepa roots

The present study evaluates the cytogenetic effects of both silver and gold nanoparticles on the root cells of Allium cepa. In this study, the root cells of Allium cepa were treated with both gold and silver nanoparticles of different concentrations (1?mg/L, 5?mg/L and 10?mg/L) along with control for 72?h. Experimental results revealed that after 72?h of exposure, a significant decrease in mitotic index (MI) from 68% (control) to 52.4% (1?mg/L), 47.3% (5?mg/L) and 41.4% (10?mg/L) for gold nanoparticles and 57.1% (1?mg/L), 53% (5?mg/l), 55.8% (10?mg/L) for silver nanoparticles. Through minute observation of the photograph, it was recorded that some specific chromosomal abnormalities such as stickiness of chromosome, chromosome breaks, nuclear notch, and clumped chromosome at different exposure conditions. Therefore, present results clearly suggest that Allium cepa root tip assay could be a viable path through which negative impact of both gold and silver nanoparticles can be demonstrated over a wide range of concentrations.     

Evaluation of silver nanoparticles in cosmeceutical and potential biosafety complications

Silver nanoparticles are well received in the cosmeceutical industry due to their broad spectrum of pharmacology applications. Research on the therapeutic properties exhibited by silver nanoparticles revealed that the antimicrobial and anti-inflammatory properties are the main attraction in the establishment of nanocosmeceutical products whereby their mechanisms of action are reviewed in this paper. In addition, studies on other uses of silver nanoparticles acknowledged that the particles act as antifungal agents in nail polishes and pigments in coloured beauty products such as lipsticks and eye shadows. Despite the extensive use of silver nanoparticles in the cosmetic line, there are still limited resources on the mechanism of actions and the effect of the particles on the bio-functionality of the body. The safety of silver nanoparticles could be comprehended from their skin penetration ability and toxicity to the human body in which it could be justified that both features are mainly influenced by the morphology of the particles and the method of application. This article summarizes exclusively on the synthesis of silver nanoparticles, the biomedical mechanisms and applications as well the limitations with respect to skin penetration ability and toxicity effects which will contribute significantly to the vast research on the association of nanotechnology and cosmetics.