In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium Escherichia coli, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag+ (in the form of AgNO3). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli.

http://www.omnis-mg.hr/Radovi/EC-oblik-koreja.pdf

Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the Gram-negative bacterium Escherichia coli.

The major strategies for designing surfaces that prevent fouling due to proteins, bacteria, and marine organisms are reviewed. Biofouling is of great concern in numerous applications ranging from biosensors to biomedical implants and devices, and from food packaging to industrial and marine equipment. The two major approaches to combat surface fouling are based on either preventing biofoulants from attaching or degrading them. One of the key strategies for imparting adhesion resistance involves the functionalization of surfaces with poly(ethylene glycol) (PEG) or oligo(ethylene glycol). Several alternatives to PEG-based coatings have also been designed over the past decade. While protein-resistant coatings may also resist bacterial attachment and subsequent biofilm formation, in order to overcome the fouling-mediated risk of bacterial infection it is highly desirable to design coatings that are bactericidal. Traditional techniques involve the design of coatings that release biocidal agents, including antibiotics, quaternary ammonium salts (QAS), and silver, into the surrounding aqueous environment. However, the emergence of antibiotic- and silver-resistant pathogenic strains has necessitated the development of alternative strategies. Therefore, other techniques based on the use of polycations, enzymes, nanomaterials, and photoactive agents are being investigated. With regard to marine antifouling coatings, restrictions on the use of biocide-releasing coatings have made the generation of nontoxic antifouling surfaces more important. While considerable progress has been made in the design of antifouling coatings, ongoing research in this area should result in the development of even better antifouling materials in the future.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201001215

Antifouling coatings: recent developments in the design of surfaces that prevent fouling by proteins, bacteria, and marine organisms.

Strain specificity in antimicrobial activity of silver and copper nanoparticles

In the present study, we report the preparation of silver nanoparticles in the range of 10‐15 nm with increased stability and enhanced anti-bacterial potency. The morphology of the nanoparticles was characterized by transmission electron microscopy. The antibacterial effect of silver nanoparticles used in this study was found to be far more potent than that described in the earlier reports. This effect was dose dependent and was more pronounced against gram-negative bacteria than gram-positive organisms. Although bacterial cell lysis could be one of the reasons for the observed antibacterial property, nanoparticles also modulated the phosphotyrosine profile of putative bacterial peptides, which could thus affect bacterial signal transduction and inhibit the growth of the organisms.

http://iopscience.iop.org/article/10.1088/0957-4484/18/22/225103/pdf

Characterization of enhanced antibacterial effects of novel silver nanoparticles

Silver nanoparticles with different sizes (7, 29, and 89 nm mean values) were synthesized using gallic acid in an aqueous chemical reduction method. The nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), and ultraviolet–visible (UV–Vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopies studies (TEM) we observed that silver nanoparticles have spherical (7 and 29 nm) and pseudospherical shape (89 nm) with a narrow size distribution. The sizes of the silver nanoparticles were controlled by varying some experimental conditions. It was found that the antibacterial activity of the nanoparticles varies when their size diminishes.

Synthesis and antibacterial activity of silver nanoparticles with different sizes

The bactericidal action of silver (0) nanoparticles and amoxicillin on Escherichia coli is studied, respectively Increasing concentration of both amoxicillin (0–0525 mg ml−1) and silver nanoparticles (0–40 µg ml−1) showed a higher antibacterial effect in Luria–Bertani (LB) medium Escherichia coli cells have different bactericidal sensitivity to them When amoxicillin and silver nanoparticles are combined, it results in greater bactericidal efficiency on Escherichia coli cells than when they were applied separately Dynamic tests on bacterial growth indicated that exponential and stationary phases are greatly decreased and delayed in the synergistic effect of amoxicillin and silver nanoparticles In addition, the effect induced by a preincubation with silver nanoparticles is examined The results show that solutions with more silver nanoparticles have better antimicrobial effects One hypothesized mechanism is proposed to explain this phenomenon

https://iopscience.iop.org/article/10.1088/0957-4484/16/9/082/pdf

Synergistic antibacterial effects of β-lactam antibiotic combined with silver nanoparticles

Amorphous FeNiPt nanoparticles with tunable length for electrocatalysis and electrochemical determination of thiols

Two-dimensional handkerchief-like nanostructures of Ni and NiCo magnetic amorphous alloys have been synthesized by a double composite structure-inducing template. High resolution transmission electron microscopy was used to characterize the morphology and the dimensions. The self-assembly of fine handkerchief-like Ni and NiCo nanoalloys is attributed to the cooperation between ion-selected delivery of a hard collodion membrane by nitro-group chemical complexations and the size-controlled action of a reverse microemulsion. Importantly, the coordinations of ethylenediamine with Ni2+ and Co2+ can restrict the structure-inducing action. The phase transformation behavior was recorded by differential scanning calorimetry. Substituting Co for Ni can slow phase transformation, and the kinetic ordering temperature increases with the Co concentration increasing. The magnetic property measurement results show that the saturation magnetizations increase as the Co concentration is increased, but the coercivity is not ...

Nanostructures of Ni and NiCo Amorphous Alloys Synthesized by a Double Composite Template Approach

Two novel dendritic superstructural and fractal BaCrO4 crystals were simultaneously synthesized in the same reaction system via facile vegetal bi-templates, mung bean sprouts (MBS). The two dendritic crystals in different shapes were grown on the outer surface and the inner stem wall of MBS. The two BaCrO4 dendrites are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). The luminescent property indicates that the products have a broad emission band peak may have applications in an electronic light device. A presumable mechanism is also given.

Simultaneous Synthesis of Dendritic Superstructural and Fractal Crystals of BaCrO4 by Vegetal Bi-templates

In this paper, a novel method is reported by which semiconductor materials are synthesized via controlled organism membranes. Semiconductor lead selenide nanorods and nanotubes have been successfully prepared simultaneously through living bio-membrane bi-templates of the mungbean sprout. The lead selenide nanorods are approximately 45 nm in diameter, and up to 1100 nm in length; all of them are single crystalline in structure. Lead selenide nanotubes are 50 nm in diameter, and up to 2000 nm in length, and are poly-crystalline in structure. The characteristics of the products are illustrated by various means, and their possible formation mechanism is explored.

https://iopscience.iop.org/article/10.1088/0957-4484/15/12/033/pdf

Qingsheng Wu

Papers

Synergistic antibacterial effects of β-lactam antibiotic combined with silver nanoparticles

Amorphous FeNiPt nanoparticles with tunable length for electrocatalysis and electrochemical determination of thiols

Nanostructures of Ni and NiCo Amorphous Alloys Synthesized by a Double Composite Template Approach

Simultaneous Synthesis of Dendritic Superstructural and Fractal Crystals of BaCrO4 by Vegetal Bi-templates

Living bio-membrane bi-template route for simultaneous synthesis of lead selenide nanorods and nanotubes