Compositions including pH sensitive lipid vesicles comprised of a lipid layer, an agent, and an organic halogen such that the agent is released from the vesicles after exposure to ionizing radiation. Methods of delivering the agent to a target in a subject using the compositions provided herein are also described. The methods allow for controlled release of the agent. The timing of release of the agent from the lipid vesicle may be controlled as well as the location of release by timing and localizing the exposure to ionizing radiation exposure.
1. A pH sensitive lipid vesicle composition configured for the controlled release of an agent upon exposure to ionizing radiation, the composition comprising: a lipid layer, the lipid layer comprising a pH sensitive phospholipid selected from the group consisting of a phosphatidylethanolamine, a phosphatidylcholine, and a combination thereof, and an aqueous medium, the aqueous medium comprises the agent and an organic halogen capable of interacting with ionizing radiation to increase the acidity of the aqueous medium, wherein the organic halogen is selected from chloral hydrate and bromal hydrate and has a concentration between 0.01 M and 2 M in the aqueous medium within the vesicle.