Synthesis of pH-responsive PEGylated nanogels platinum nanoparticles (PtNPs: <2 nm) was successfully carried out through the reduction of K2PtCl6 within the PEGylated nanogels constructed from cross-linked poly[2-(N,N-diethylamino)ethyl methacrylate] (PDEAMA) core and tethered PEG chains. The resulting PEGylated nanogels containing PtNPs showed significant catalytic activity for reactive oxygen species (ROS) in response to skin-environmental pH (acid), whereas the almost no catalytic activity for ROS was observed at physiological pH due to the volume phase transition of the PDEAMA gel core. Thus, pH-responsive and PEGylated nanogel containing PtNPs can be utilized to the skin-specific ROS-scavengers for the skin aging. (c) 2007 Elsevier Ltd. All rights reserved.