Photoswitchable bactericidal effects from novel silica-coated silver nanoparticles

Abstract

The enhancement of the electromagnetic field in the surroundings of nanoparticles via surface plasmon resonance offers promising possibilities for biomedical applications. Here we report on the selective triggering of antibacterial activity using a new type of silver nanoparticles coated with silica, Ag@silica, irradiated at their surface plasmon frequency. The nanoparticles are able to bind readily to the surface of bacterial cells, although this does not affect bacterial growing since the silica shell largely attenuates the intrinsic toxicity of silver. However, upon simultaneous exposure to light corresponding to the absorption band of the nanoparticles, bacterial death is triggered selectively on the irradiated zone. Because of the low power density used in the treatments, we discard thermal effects as the cause of cell killing. Instead, we propose that the switched toxicity is due to the enhanced electromagnetic field in the proximity of the nanoparticles, which either directly (through membrane perturbation) or indirectly (through induced photochemical reactions) is able to cause cell death.

Enhancement of the Antibacterial Efficiency of Silver Nanoparticles against Gram-Positive and Gram-Negative Bacteria Using Blue Laser Light

“…Panas et al [19] reported that excitation of Ag/TiO 2 NPs by blue laser light at 455 nm for 5 min inhibited the proliferation of Streptococcus salivarius due to high photocatalytic activity that irreversibly damages cell walls and membranes. In another study, Fuertes et al [20] analyzed the antibacterial activity of Ag-NPs coated with porous silica and irradiated at their SPR frequency of 387 nm, which induced production of toxic ROS and subsequent cell death in E. coli. They suggested that a possible mechanism for the synergistic effect of Ag-NPs with laser light is the production of cytotoxic ROS by the visible blue light resulting in destruction of the bacterial cell membrane.…”

Thin films of Ag–Au nanoparticles dispersed in TiO2: influence of composition and microstructure on the LSPR and SERS responses

“…LSPR leads to the appearance of strong absorption bands, the enhancement of the electromagnetic (EM) field near the nanoparticles and the appearance of scattering to the far field [1,5]. Beyond some known decorative applications [6,7], plasmonic effects are important in a wide range of technological domains, which include plasmon-based photodetectors [8] and modulators [9], gas sensors [10][11][12], biosensors [13][14][15], photothermal therapy [16], photodynamic therapy [17], LSP-enhanced solar cells [18,19], surface enhanced Raman spectroscopy (SERS) [20][21][22], plasmonic nanoscopy [23], thermal emitters [24], light-emitting diodes [25] and magnetic storage [26].…”