Can silver nanoparticles be useful as potential biological labels?

Abstract

Silver (Ag) nanoparticles have unique plasmon-resonant optical scattering properties thatare finding use in nanomedical applications such as signal enhancers, optical sensors, andbiomarkers. In this study, we examined the chemical and biological propertiesof Ag nanoparticles of similar sizes, but that differed primarily in their surfacechemistry (hydrocarbon versus polysaccharide), in neuroblastoma cells for theirpotential use as biological labels. We observed strong optical labeling of the cellsin a high illumination light microscopy system after 24 h of incubation due tothe excitation of plasmon resonance by both types of Ag nanoparticle. Surfacebinding of both types of Ag nanoparticle to the plasma membrane of the cellswas verified with scanning electron microscopy as well as the internalization andlocalization of the Ag nanoparticles into intracellular vacuoles in thin cell sections withtransmission electron microscopy. However, the induction of reactive oxygen species(ROS), degradation of mitochondrial membrane integrity, disruption of the actincytoskeleton, and reduction in proliferation after stimulation with nerve growthfactor were found after incubation with Ag nanoparticles at concentrations of25 µg ml−1 or greater, with a more pronounced effect produced by the hydrocarbon-based Agnanoparticles in most cases. Therefore, the use of Ag nanoparticles as potential biologicallabels, even if the surface is chemically modified with a biocompatible material, should beapproached with caution.