This disclosure provides IR700-molecule conjugates and methods of their use to remove (e.g., separate or isolate) a target from a sample in vivo or from a subject in vitro. It is shown herein that exposure of IR700 to near infrared (NIR) light removes a portion of IR700, changing it from a hydrophilic molecule, to one that is hydrophobic, resulting in aggregation of IR700 and anything bound to it. For example, the disclosed IR700-molecule conjugates and methods provide photo-controlled ways to control the pharmacokinetics of a drug in vivo, and can be used to remove undesired agents from environmental or food samples or to isolate target molecules in a laboratory.