The potential of antimicrobial peptides as biocides

Antimicrobial peptides constitute a diverse class of naturally occurring antimicrobial molecules which have activity against a wide range of pathogenic microorganisms. Antimicrobial peptides are exciting leads in the development of novel biocidal agents at a time when classical antibiotics are under intense pressure from emerging resistance, and the global industry in antibiotic research and development stagnates. This review will examine the potential of antimicrobial peptides, both natural and synthetic, as novel biocidal agents in the battle against multi-drug resistant pathogen infections.     

Mechanical and antimicrobial properties of multilayer films with a polyethylene/silver nanocomposite layer

A layer of a polyethylene–silver nanoparticles composite was deposited on a five layer barrier film structure. Different methods were used for the nanocomposite layer deposition: laminating, casting, and spraying over the multilayer structure. For the casting and spraying methods, the silver nanoparticles were previously dispersed in the polymer solution, with the assistance of ultrasound energy. The effect of silver nanoparticles and deposition method on the barrier, mechanical, and optical properties of the multilayer films was evaluated. The efficiency of silver ion release from the PE‐Silver nanocomposite deposited on the multilayer films and their antimicrobial characteristics were investigated and discussed. The silver ion release and biocide effect of the multilayer films was found to be dependant on the silver nanoparticle content and on the deposition method used. The observed results could be helpful in the design of industrial films for packaging. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and study of cellulose acetate membranes modified with linear polymers covalently bonded to Starburst polyamidoamine dendrimers

Novel ion‐selective membranes were prepared by means of the noncovalent modification of a cellulose acetate (CA) polymer with either poly(ethylene‐alt‐maleic anhydride) or poly(allylamine hydrochloride) chains covalently linked to Starburst amine‐terminated polyamidoamine (PAMAM) dendrimers generations 4 and 3.5, respectively. Linear polymer incorporation within the porous CA membrane was performed with mechanical forces, which resulted in modified substrates susceptible to covalent adsorption of the relevant dendritic materials via the formation of amide bonds with a carbodiimide activation agent. The membranes thus prepared were characterized by chemical, physical, and spectroscopic measurements, and the results indicate that the dendrimer peripheral functional groups were the species that participated in the ion‐exchange events. The prepared materials were also evaluated for their ion‐exchange permeability with sampled current voltammetry experiments involving cationic and anionic species {[Ru(NH₃)₆]³⁺ and [Fe(CN₆)]^3?, respectively} as redox probe molecules under different pH conditions. As expected, although permeability was favored by opposite charges between the dendrimer and the electroactive probe, a clear blocking effect took place when the charge in the dendritic polymer and the electroactive complex was the same. Electrochemical impedance spectroscopy measurements, on the other hand, showed that the PAMAM‐modified membranes were characterized by good selectivity and low resistance values for multivalent ions compared to a couple of commercial ion‐exchange membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of chitosan‐graft‐(methyl methacrylate)/Ag nanocomposite with antimicrobial activity

It has been found that composites of chitosan (CS) and Ag nanoparticles can exhibit excellent antibacterial activities. However, the weak mechanical performances of these composite materials limit their wide application. Grafting of vinyl monomers onto CS is one of the most effective methods to improve the performances of CS without sacrificing its properties. A nanocomposite of chitosan‐graft‐(methyl methacrylate) (CS‐g‐MMA) containing Ag nanoparticles was prepared by in situ chemical reduction of Ag ions in an aqueous acetic acid solution of CS and graft copolymerization of MMA onto CS. Transmission electron micrographs, X‐ray diffraction patterns and UV‐visible spectra of the nanocomposite confirmed the formation of Ag nanocrystals. X‐ray photoelectron spectroscopy proved that Ag? O bonds exist in the composite. Thermogravimetric analysis/differential scanning calorimetry showed that the decomposition temperature of CS was 319.8 °C while that of the CS‐g‐MMA/Ag composite shifted to a higher temperature of 422.1 °C. Antimicrobial experiments showed that the antimicrobial rates of the CS‐g‐MMA/Ag composite to E. coli, B. subtilis, S. aureus and P. aeruginosa were 93–98%. CS molecules can act as stabilizing agents to prevent the aggregation of Ag nanoparticles in the process of synthesizing CS‐g‐MMA/Ag nanocomposites. The antimicrobial activity of the as‐prepared nanocomposites is higher than that of CS alone. Copyright © 2009 Society of Chemical Industry     

Synergistic antimicrobial effects of polyaniline combined with silver nanoparticles

Silver/polyaniline nanocomposites (Ag NPs/PANI) containing PANI nanofiber and Ag nanoparticles were synthesized by one-step approach without using any extra reducing agent or surfactant and applied to new antimicrobial agents. Morphologies and crystallinity of the nanocomposites were characterized with SEM and XRD. The results showed that the average diameter of the PANI nanofibers is around 50–150 nm, and the average particle size of Ag NPs is around 100 nm. The crystallinity of PANI gets better with increasing silver nitride concentration. UV–vis absorption spectroscopy analysis indicated that the Ag NPs have some effect on the microstructure of PANI. The antimicrobial properties of Ag NPs/PANI against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus and fungous Yeast were evaluated using viable cell counts. The test results demonstrated that Ag NPs/PANI have enhanced antimicrobial efficacy compared to that of pure Ag NPs or pure PANI under the same test condition. The mechanism of the synergistic antimicrobial effect of Ag NPs with PANI was also proposed. In addition, thermal gravity analysis indicated that pure PANI and Ag NPs/PANI exhibit better thermal stability. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

绿色合成桑叶银纳米粒及其抗菌抗癌活性

为了更好地开发出具有良好物理化学及生物活性的银纳米粒,利用桑叶水提取物,通过绿色方法制得桑叶银纳米粒。以AgNO3浓度、反应温度、桑叶水提物的用量、pH以及反应时间为影响因素,优化桑叶银纳米粒最佳合成条件;通过UV-Vis,SEM及FTIR等对产物进行结构表征;通过测定抑菌圈、最小抑菌浓度和细胞毒实验评价其抗菌及抗癌活性。结果显示,最佳制备条件为：AgNO3浓度5 mmol/L、反应温度35 ℃、桑叶水提液与AgNO3溶液体积比1∶5、反应体系pH 11.0及反应时间6 h。在此条件下制备的桑叶银纳米粒为大小均一的球形,平均粒径（48.78 ± 0.39） nm,电位（-27.8 ± 2.00） mV;相比于桑叶水提物,桑叶银纳米粒对大肠杆菌、铜绿假单胞菌,金黄色葡萄球菌、枯草杆菌及白色念球菌均表现较好的抑菌效果,其最小抑菌浓度分别为12.50、25.00、25.00、100.00和100.00 mg/L;桑叶银纳米粒对人宫颈癌（IC50为60.63 mg/L）,人肝癌（IC50为 26.98 mg/L）和人乳腺癌（IC50为18.65 mg/L）细胞有很好的抑制作用。     

绿色合成桑叶银纳米粒及其抗菌抗癌活性

为了更好地开发出具有良好物理化学及生物活性的银纳米粒,利用桑叶水提取物,通过绿色方法制得桑叶银纳米粒.以AgNO3浓度、反应温度、桑叶水提物与AgNO3溶液体积比、pH以及反应时间为影响因素,优化桑叶银纳米粒最佳合成条件;通过UV-Vis、SEM及FTIR等对产物进行结构表征;通过测定抑菌圈、最小抑菌浓度和细胞毒实验评价其抗菌及抗癌活性.结果显示,最佳制备条件为:AgNO3浓度5 mmol/L、反应温度35℃、桑叶水提液与AgNO3溶液体积比1:5、反应体系pH 11.0及反应时间6 h.在此条件下制备的桑叶银纳米粒为大小均一的球形,平均粒径(48.78±0.39)nm,电位(–27.8±2.00)mV;相比于桑叶水提物,桑叶银纳米粒对大肠杆菌、铜绿假单胞杆菌、金黄色葡萄球菌、枯草芽孢杆菌及白色念球菌均表现出较好的抑菌效果,其抑菌圈分别为(11.39±1.02)、(10.50±0.92)、(10.50±0.61)、(7.90±0.79)和(8.31±0.52)mm;桑叶银纳米粒对人宫颈癌细胞〔半数抑制浓度(IC50)为60.63 mg/L〕、人肝癌细胞(IC50为26.98 mg/L)和人乳腺癌细胞(IC50为18.65 mg/L)有很好的抑制作用.     

Preparation of Ag nanoparticles in the presence of low generational poly(ester‐amine) dendrimers

Stable Ag nanoparticles of 10–20 nm were prepared by reduction of AgNO₃ with NaBH₄ in water solution in the presence of low generational hydroxyl‐ terminated poly(ester‐amine) dendrimer G1.0 (OH)₁₆ and amino‐terminated poly(ester‐amine) dendrimer G1.5 (NH₂)₈ by optimizing preparation conditions. UV–vis absorption spectra and transmission electron microscopy were adopted to characterize absorption properties of Ag⁺/dendrimer complex, Ag/dendrimer nanocomposite aqueous solutions, and the morphology of the formed Ag nanoparticles, respectively. The results showed that the size of the Ag particles increased with Ag⁺/dendrimer molar ratio, and the size of Ag nanoparticles in Ag/G1.0 (OH)₁₆ system was larger than that of Ag nanoparticles in Ag/G1.5 (NH₂)₈ system, while the polydispersities of two systems were similar. Moreover, the Ag/G1.5 (NH₂)₈ nanocomposite system was more stable than the Ag/G1.0 (OH)₁₆ one. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 422–426, 2007     

A structure/function study of polyaminoamide dendrimers as silica scale growth inhibitors

Dendrimers have attracted immense attention during the last decade due to their interesting properties both from a basic and an applied research viewpoint. Encapsulation of metal nanoparticles for catalysis, drug delivery and light harvesting are only some applications of dendrimers that are breaking new ground. A novel application of dendrimer technology is described in the present paper that relates to industrial water treatment. Industrial water systems often suffer from undesirable inorganic deposits. These can form either in the bulk or on metallic surfaces, such as heat exchangers or pipelines. Silica (SiO₂) scale formation and deposition is a major problem in high‐silica‐containing cooling waters. Scale prevention rather than removal is highly desired. In this paper, benchtop screening tests on various silica inhibition chemistries are reported, with emphasis on materials with a dendrimeric structure. Specifically, the inhibition properties of commercially available STARBURST^® polyaminoamide (PAMAM) dendrimers generations 0.5, 1, 1.5, 2, and 2.5 are investigated in detail together with other commonly‐used scale inhibitors. Experimental results show that inhibition efficiency largely depends on structural features of PAMAM dendrimers such as generation number and nature of the end groups. PAMAM dendrimers are effective inhibitors of silica scale growth at 40 ppm dosage levels. PAMAM dendrimers also act as silica nucleators, forming SiO₂–PAMAM composites. This occurs because the SiO₂ formed by incomplete inhibition interacts with cationic PAMAM‐1 and ‐2. The general scope of silica formation and inhibition in industrial waters is also discussed. Copyright © 2005 Society of Chemical Industry     

High efficiency antimicrobial cellulose‐based nanocomposite hydrogels

Carboxymethyl cellulose hydrogels were developed through crosslinking process using maleic, succinic, or citric acids. The swelling capacities of the obtained hydrogels have been controlled through variation of the crosslinking reaction conditions. Further enhancement of the swelling properties was achieved by additional blending step of the carboxymethyl cellulose with polyethylene glycol. Biofunctionalization of the hydrogels was achieved through “in situ” incorporation of the silver nanoparticles during the crosslinked reaction. Chemical structure verifications and morphological characterizations of the hydrogels were performed using FTIR, XRD, EDX, and SEM analyses. Finally, the antimicrobial activity of the loaded silver hydrogels against G+ve, G?ve, and yeast Candida albicans was demonstrated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42327.     

Preparation of silver nanoparticle functionalized polyamide fibers with antimicrobial activity and electrical conductivity

In this work, silver nanoparticle functionalized polyamide 6 (PA6) fibers were prepared using the electroless plating method. The surface of PA6 fibers was modified by exploiting dopamine/CuSO₄/H₂O₂ system prior to electroless plating to enhance the bonding force between the fiber and the silver nanoparticles. It was found that both the formation rate and the chemical stability of polydopamine (PDA) coatings on the PA6 fiber surface were improved by the introduction of CuSO₄/H₂O₂. The results confirmed the successful deposition of silver nanoparticles on PA6 fiber surface and the average particle diameter of 223 nm. Compared with uncoated fibers, the silver plated PA6 fibers exhibited excellent antimicrobial activity to both Escherichia coli and Staphylococcus aureus (with an antimicrobial efficiency of 99.9% and 100%, respectively). The electrical resistance of the silver coated PA6 fibers reached 0.98 Ω over a length of 1 cm, indicating a good electrical conductivity. In particular, coating durability of the formed silver layer was investigated by subjecting the fibers to various mechanical deformations, and the results showed that the formed silver layer was maintained well after 50 times of cyclic stretching at a constant displacement of 10 mm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47584.     

异氰酸酯型树枝状大分子的合成及应用

树枝状大分子在化学、生物医学、环境保护等领域应用广泛,是近年来发展迅速的一类新型材料。介绍了树枝状大分子的研究进展、结构性能、合成方法及其应用,论述了以异氰酸酯化合物为新型单体的树枝状大分子的合成。     

负载硅钨杂多酸纳米银修饰电极的电化学性质研究

以硅钨杂多酸作为光催化还原剂制备了纳米银(SiW12-NS)。用PVP作偶联剂,将SiW12-NS修饰到玻碳电极表面,用循环伏安法(CV)研究其电化学行为。结果表明,修饰电极具有良好的电化学响应和电极稳定性,对BrO3-,NO2-具有良好的电催化还原性能。     

Antitumor efficacy of doxorubicin encapsulated within PEGylated poly(amidoamine) dendrimers

We report here a general approach to using poly(amidoamine) (PAMAM) dendrimers modified with polyethylene glycol (PEG) as a platform to encapsulate an anticancer drug doxorubicin (DOX) for in vitro cancer therapy applications. In this approach, PEGylated PAMAM dendrimers were synthesized by conjugating monomethoxypolyethylene glycol with carboxylic acid end group (mPEG‐COOH) onto the surface of generation 5 amine‐terminated PAMAM dendrimer (G5.NH₂), followed by acetylation of the remaining dendrimer terminal amines. By varying the molar ratios of mPEG‐COOH/G5.NH₂, G5.NHAc‐mPEG_n (n = 5, 10, 20, and 40, respectively) with different PEGylation degrees were obtained. We show that the PEGylated dendrimers are able to encapsulate DOX with approximately similar loading capacity regardless of the PEGylation degree. The formed dendrimer/DOX complexes are water soluble and stable. In vitro release studies show that DOX complexed with the PEGylated dendrimers can be released in a sustained manner. Further cell viability assay in conjunction with cell morphology observation demonstrates that the G5.NHAc‐mPEG_n/DOX complexes display effective antitumor activity, and the DOX molecules encapsulated within complexes can be internalized into the cell nucleus, similar to the free DOX drug. Findings from this study suggest that PEGylated dendrimers may be used as a general drug carrier to encapsulate various hydrophobic drugs for different therapeutic applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40358.     

Preparation and characterization of silver nanoparticles with dendrimers as templates

In this study, crystal silver nanoparticle clusters, prepared by the reduction of AgNO₃ in the presence of third-to-sixth-generation dendrimers with a trimesyl core, were characterized with ultraviolet–visible spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The results showed that the particle size of the silver nanoparticles was considerably affected by the generation of the dendrimers as well as the dendrimer concentration. When the concentration ratios of Ag⁺ to the third-to-sixth-generation dendrimers were all 4 : 1, the average diameters of the obtained particles were 6.7, 6.0, 5.2, and 4.3 nm, respectively. The data from high-resolution transmission electron microscopy and electron diffraction indicated that the particles belonged to a simple cubic crystal structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

New nanohybrids from poly(propylene imine) dendrimer stabilized silver nanoparticles on multiwalled carbon nanotubes for effective catalytic and antimicrobial applications

Five types of multiwalled carbon nanotubes noncovalently functionalized with poly (propylene imine) dendrimer (PPI (G2))-silver nanoparticle hybrids were prepared by varying the [Ag⁺] load from 2 to 6 mM. These nanohybrids were characterized with FTIR, UV-Vis, FESEM, EDS, HRTEM and Raman analyses. The catalytic potential was studied through the reduction of 4-nitrophenol as a model reaction under pseudo first-order reaction conditions. The calculated k_obs value (16.94 × 10^?2 min^?1) reveals that the 4 mM [Ag⁺] loaded catalyst showed higher efficiency than with rest of the catalysts. Further, the in vitro antimicrobial activities of all nanohybrids were inspected against Pseudomonas aeruginosa and Staphylococcus aureus.     

Adsorption of Silver Nanoparticles onto Different Surface Structures of Chitin/Chitosan and Correlations with Antimicrobial Activities

Size-controlled spherical silver nanoparticles (Ag NPs) can be simply prepared by autoclaving mixtures of glass powder containing silver with glucose. Moreover, chitins with varying degrees of deacetylation (DDAc < 30%) and chitosan powders and sheets (DDAc > 75%) with varying surface structure properties have been evaluated as Ag NP carriers. Chitin/chitosan-Ag NP composites in powder or sheet form were prepared by mixing Ag NP suspensions with each of the chitin/chitosan-based material at pH 7.3, leading to homogenous dispersion and stable adsorption of Ag NPs onto chitin carriers with nanoscale fiber-like surface structures, and chitosan carriers with nanoscale porous surface structures. Although these chitins exhibited mild antiviral, bactericidal, and antifungal activities, chitin powders with flat/smooth film-like surface structures had limited antimicrobial activities and Ag NP adsorption. The antimicrobial activities of chitin/chitosan-Ag NP composites increased with increasing amounts of adsorbed Ag NPs, suggesting that the surface structures of chitin/chitosan carriers strongly influence adsorption of Ag NPs and antimicrobial activities. These observations indicate that chitin/chitosan-Ag NPs with nanoscale surface structures have potential as antimicrobial biomaterials and anti-infectious wound dressings.     

纳米AgBr/壳聚糖杂化抗菌材料的制备和抑菌性研究

用壳聚糖衍生物(CPNP)和溴化银纳米粒子合成了一种新型抗菌材料,通过IR、TGA、SEM、EDS、XRD等对其进行了表征。这种抗菌材料具有很好的水溶性。用最低抑菌浓度和抑菌圈试验对该材料进行了抑菌性能测试,结果表明,该材料对金黄色葡萄球菌和大肠杆菌具有很好的抑制活性。     

Synthesis of silver nanocrystals by a modified polyol method

A modification of the polyol method has been shown to result in improved efficiency and enhanced kinetics for the synthesis of silver nanocrystals when compared with the traditional polyol method. The Ag nanocrystals produced were characterized using X‐ray diffraction and transmission electron microscopy. Accordingly, the exhibited Ag crystal structure, corresponding lattice constants, and resultant particle sizes were determined by these means. In addition, using Fourier transform infrared spectroscopy, it was found that a solid‐state reaction between the AgNO₃ and the Poly (vinylpyrrolidone) (PVP) takes place prior to their dissolution in ethylene glycol. Moreover, when crystals grow under total rest conditions, they do not develop a spherical morphology as in the traditional polyol method, but a well‐defined geometric shape showing preferential crystallographic growth directions. Under the experimental conditions of this work, the exhibited nanocrystal shapes were quasi‐planar hexagonal. Apparently, PVP interacts with the FCC crystal structure promoting growth on the {100} preferential direction by playing the role of an atomic arranger. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Complexes of Silver(I) Ions and Silver Phosphate Nanoparticles with Hyaluronic Acid and/or Chitosan as Promising Antimicrobial Agents for Vascular Grafts

Polymers are currently widely used to replace a variety of natural materials with respect to their favourable physical and chemical properties, and due to their economic advantage. One of the most important branches of application of polymers is the production of different products for medical use. In this case, it is necessary to face a significant disadvantage of polymer products due to possible and very common colonization of the surface by various microorganisms that can pose a potential danger to the patient. One of the possible solutions is to prepare polymer with antibacterial/antimicrobial properties that is resistant to bacterial colonization. The aim of this study was to contribute to the development of antimicrobial polymeric material ideal for covering vascular implants with subsequent use in transplant surgery. Therefore, the complexes of polymeric substances (hyaluronic acid and chitosan) with silver nitrate or silver phosphate nanoparticles were created, and their effects on gram-positive bacterial culture of Staphylococcus aureus were monitored. Stages of formation of complexes of silver nitrate and silver phosphate nanoparticles with polymeric compounds were characterized using electrochemical and spectrophotometric methods. Furthermore, the antimicrobial activity of complexes was determined using the methods of determination of growth curves and zones of inhibition. The results of this study revealed that the complex of chitosan, with silver phosphate nanoparticles, was the most suitable in order to have an antibacterial effect on bacterial culture of Staphylococcus aureus. Formation of this complex was under way at low concentrations of chitosan. The results of electrochemical determination corresponded with the results of spectrophotometric methods and verified good interaction and formation of the complex. The complex has an outstanding antibacterial effect and this effect was of several orders higher compared to other investigated complexes.