Etude et elaboration de nanoparticules metalliques (Au /Ag) pour la phototherapie.

Abstract

Silver nanoparticles (AgNPs) are known as effective diffusers and light absorbers because of their strong interactions with visible light through the surface plasmon resonance (SPR) phenomenon. The local frequency LSPR strongly depends on the size, shape and dielectric medium surrounding the nanoparticles. In this case, our work is focused on the synthesis of silver nanoparticles for medical applications. The synthesis of silver nanoparticles of different sizes was performed using different molar concentrations of AgNO 3 (0.0015, 0.0025, 0.0030, 0.0035 moles). AgNO3, PVP, benzoic acid, are used as precursor, stabilizer, reducing agent, in two different solvents (ethanol and methanol). The synthesized nanoparticles have been characterized by UV-Visible spectroscopy at different temperatures. The results show the presence of an absorption peak around 440 nm. In addition, we have shown that agglomeration is more important in methanol than in ethanol. The nanoparticles synthesized at room temperature in an ethanol solvent medium with the different concentrations of the precursor AgNO3 mentioned above were characterized with the transmission electron microscope TEM and dynamic light scattering technique DLS. It has been found that by varying the value of the ratio between AgNO 3 and PVP but keeping the same amount of benzoic acid, different forms of silver NP, such as spherical, ellipsoid, triangular, hexagonal and octahedral shapes are revealed. by TEM microscopy. The different forms of silver nanoparticles obtained on these four colloidal solutions have an aspect ratio ranging from 1 to 1.9 and an average size around 10 nm. The results obtained by the DLS dynamic light scattering technique confirmed the results obtained by TEM where they showed a homogeneous distribution of silver nanoparticles. Finally, a new, effective and inexpensive nano-therapeutic approach combining silver nanoparticles with conventional antibiotics has been studied against various multi-resistant bacteria namely : Staphylococcus aureus ,Pseudomonas aeruginosa,Acinetobacter baummanni, Echerichia coli, and coagulase-negative staphylococcus. The silver nanoparticles showed effective antibacterial activity on the tested strains, as well as synergistic antibacterial activity with different antibiotics which proved to be ineffective against these same pathogenic bacteria. We therefore found that the antibacterial activity of different antibiotics increased in the presence of silver nanoparticles. The size, shape, and concentration of silver nanoparticles seems to play an important role in their mechanisms of action.