Intelligent colloidal particles have been widely used as carriers for delivery of bioactive molecules due to the ability of controlled release. However, attention is mainly paid to the effects of their payloads, whereas the impacts of carriers are largely ignored. In this study, photo-responsive polyethylene glycol (PEG) microparticles were fabricated by using 8-arm-PEG with terminal amine groups (8-arm-PEG-NH2) and a photo-cleavable cross-linker. Due to the cleavable C-O bond in the cross-linker, under UV irradiation the PEG particles could be decomposed gradually, leading to particle swelling and eventual disappearance. The PEG particles could be internalized by smooth muscle cells and HepG2 cells, and located in lysosomes. Their intracellular photo-response induced significant decrease of cell viability and increase of reactive oxygen species level. (C) 2017 Elsevier Inc. All rights reserved.