Inspired by the spontaneous cyclization of ornithine in peptides, polyesters containing protected ornithine (Orn) side chains along the backbone were synthesized and shown to degrade rapidly upon deprotection through intramolecular cyclization. A new ornithine-based poly(ester amide) PEA 1 and a lysine-based control PEA 2, both bearing the light-sensitive protecting group o-nitrobenzyl alcohol (ONB), were synthesized. Tert-butyl carbamate (Boc)-protected versions 1-Boc and 2-Boc were also synthesized for proof of concept. GPC confirmed that 1-Boc degrades over 40 times faster than 2-Boc following deprotection into the designed intramolecular cyclization products. Finally, TEM visualization of particles made from 1 encapsulating iron oxide nanoparticles reveals complete disruption of nanoparticles and release of payload within a day upon UV irradiation. (C) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3783-3790