Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compounds, including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-negative bacteria using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of approximately 1-10 nm.

https://iopscience.iop.org/article/10.1088/0957-4484/16/10/059/pdf

The bactericidal effect of silver nanoparticles

Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria

Silver nanoparticles as a new generation of antimicrobials.

/pdf/antimicrobial-effects-of-silver-nanoparticles-57y1xrlo33.pdf

Antimicrobial effects of silver nanoparticles

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 surface properties of clay minerals modified by intensive dry milling — revisited

Electrokinetic potentials of clay surfaces modified by polymers

This paper discusses the formation of whiting events, drifting milky clouds of water, and their role in the formation of recent aragonite sediments in a semi-enclosed, karstic, marine lake on the island of Mljet (Adriatic Sea). This study is based on detailed structural, morphological and sedimentological characterization of, and strontium distribution in, particles originating from suspended matter and sediments. The particles were examined by X-ray diffraction and electron diffraction analyses, scanning and transmission electron microscopy, as well as electron microprobe energy dispersive X-ray analyses and atomic absorption spectroscopy. Morphological features, granulometric characteristics, strontium enrichment and characteristic details of the aragonite structure in the needle-like particles were identical in both the suspended matter collected during whiting events and in the bottom sediments. The whiting events, which occasionally occurred in surface waters, were found to be sites of short-term active authigenic aragonite precipitation and the main source of fine-grained aragonite mud. This study exemplifies the role of biologically induced inorganic precipitation processes in the formation of recent aragonite mud in a restricted Mediterranean environment.

Whiting events and the formation of aragonite in Mediterranean Karstic Marine Lakes: new evidence on its biologically induced inorganic origin

A semiconductor nanoparticle for use in analysis of biological samples is described. This semiconductor nanoparticle is composed of an aminodextran which is bound to at least one nanoparticle of the formula (X Y) n wherein X is selected from the group comprising Cd 2+ , Hg 2+ , and Zn 2+ and combinations thereof, and Y is selected from the group comprising S 2− , Se 2− and Te 2− and combinations thereof; and n=approximately 50 to 1000. Also provided are methods of making these semiconductor nanoparticles and methods of making conjugates composed of these semiconductor nanoparticles linked to ligands. Also described are uses for the conjugates in a variety of biological assays.

Semiconductor nanoparticles for analysis of blood cell populations and methods of making same

Water-dispersible Amdex–CdSe nanoparticle complexes with sufficient luminescence intensity were prepared at room temperature by rapidly mixing aqueous solutions of either sodium selenide or selenourea with those of cadmium chloride in the presence of amino-derivatized polysaccharides (Amdex) as stabilizing agent It was shown that the size of CdSe crystallites decreased with increasing content of the polymer in the precipitation process When present in a sufficient amount, Amdex was found to be an effective stabilizing and capping agent, producing CdSe nanocrystals of weak-to-medium luminescence intensity (maximum room temperature quantum yields of 15–16%) Furthermore, Amdex has proven to be an effective protective agent against photochemical degradation

Ivan Sondi

Papers

The surface properties of clay minerals modified by intensive dry milling — revisited

Electrokinetic potentials of clay surfaces modified by polymers

Whiting events and the formation of aragonite in Mediterranean Karstic Marine Lakes: new evidence on its biologically induced inorganic origin

Semiconductor nanoparticles for analysis of blood cell populations and methods of making same

Synthesis of CdSe nanoparticles in the presence of aminodextran as stabilizing and capping agent.