Silver nanoparticles with different size and shape: From synthesis to antibacterial effects

Kateryna Loza, Institute of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, Essen, Germany

Silver nanoparticles are well known for their interesting optical, biological, and electronic properties. There are many possible applications, ranging from catalysis over photonics, medical research, imaging and sensing by surface-enhanced Raman spectroscopy to energy storage and conversion. The particle properties not only depend on their size, but also on their morphology. Therefore, a shape-controlled synthesis of silver nanoparticles is of special interest.

Silver nanoparticles with different shapes but comparable size and identical surface functionalization were prepared, i.e. spheres (diameter 40–80 and 120–180 nm; two different samples), platelets (20–60 nm), cubes (140–180 nm), and rods (diameter 80–120 nm, length >1000 nm). The size of the metallic particle core was determined by electron microscopy, and the colloidal stability and the hydrodynamic particle diameter were analyzed by dynamic light scattering.

In general, all particles can be considered as very homogeneous in size and shape. The dissolution kinetics were correlated to the estimated specific surface area of the particles, where particles with a higher specific surface area dissolve faster than particles with a smaller one. By confocal laser scanning microscopy, it was shown that all particles were taken up by endocytosis of human mesenchymal stem cells. A toxic effect to these cells was observed at concentrations >12.5 mg/mL, but no shape dependence was found. Contrary to that, the toxicity towards bacteria corresponded very well to the dissolution kinetics and therefore to the particle morphology. Particles with a higher specific surface area were more toxic for bacteria than particles with smaller specific surface areas.

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