The surface modification of silver nanoparticles by phosphoryl disulfides for improved biocompatibility and intracellular uptake

In order to enhance the biocompatibility and cell affinity of metal nanoparticles for biosensing and drug delivering applications, we prepared the phospholipid derivatives containing disulfide groups to modify silver nanoparticle surfaces. By adding sodium borohydride to reduce both disulfide bonds of the derivatives and silver ions simultaneously, the generated thiol groups can be reacted with newborn silver atoms immediately to generate nanoclusters. The assemblies consisted of either phosphorylcholine (PC) or phosphorylethanolamine (PE) head groups, which made the silver clusters biocompatibile. Transmission electron microscope (TEM) and optical absorption spectra assisted in modulating reaction conditions, demonstrating that a surfactant/Ag ratio of 0.4 led to the formation of uniform, well-dispersed spherical particles about 3.8 nm in diameter. X-ray photoelectron spectra and infrared spectra also illustrated the elemental and molecular structures of nanoparticles. The insertion of rhodamine dye into the surfactant layer enabled the nanoparticles to be used as a fluorescent probe. In cell culture tests, the nanoparticles were internalized into platelet or fibroblast cells in a short period of incubation without harming the cells.