In vivo integrity of polymer-coated gold nanoparticles

Inorganic nanoparticles are frequently engineered with an organic surface coating to improve their physicochemical properties, and it is well known that their colloidal properties may change upon internalization by cells. While the stability of such nanoparticles is typically assayed in simple in vitro tests, their stability in a mammalian organism remains unknown. Here, we show that firmly grafted polymer shells around gold nanoparticles may degrade when injected into rats. We synthesized monodisperse radioactively labelled gold nanoparticles (198 Au) and engineered an 111 In-labelled polymer shell around them. Upon intravenous injection into rats, quantitative biodistribution analyses performed independently for 198 Au and 111 In showed partial removal of the polymer shell in vivo. While 198 Au accumulates mostly in the liver, part of the 111 In shows a non-particulate biodistribution similar to intravenous injection of chelated 111 In. Further in vitro studies suggest that degradation of the polymer shell is caused by proteolytic enzymes in the liver. Our results show that even nanoparticles with high colloidal stability can change their physicochemical properties in vivo. © 2015 Macmillan Publishers Limited.