We synthesize peptide-functionalized nanoparticles by growing the peptide directly from the nanoparticles in a grafting-from process. We demonstrate the procedure by grafting a short, pH and oxidation responsive peptide sequence from 300 nm silica nanoparticles. The peptide allows destabilization of the particles in response to pH by neutralization of electrostatic charge, while manipulation of oxidizing conditions in the system offers the ability to select for irreversible, covalent bonding between the particles. In one system, we show the assembly of an asymmetrically functionalized set of particles, which may have applications in the formation of binary particle networks. The method of preparing peptide-coated particles should greatly simplify existing processes used to create peptide-functionalized nanoparticles.