A heterobifunctional reactive oxygen species (ROS)-responsive linker for directed drug assembly onto and delivery from a quantum dot (QD) nanoparticle carrier was synthesized and coupled to doxorubicin using EDC/sulfo-NHS coupling. The doxorubicin conjugate was characterized using ¹H NMR and LC-MS and subsequently reacted under conditions of ROS formation (Cu²⁺/H₂O₂) resulting in successful and rapid thioacetal oxidative cleavage which was monitored using ¹H NMR. The deprotected amine linker is amenable to peptide or protein conjugation prior to QD assembly or to direct conjugation to cognate reactive groups on ligands that cap the QD surface.