Novel phototherapeutic methods and compositions are described herein. Nanoparticle-assembled microcapsules as a new type of delivery vehicle for photosensitive compounds may be synthesized through a two-step assembly process. Charged polymer chains and counterions may be combined with a photosensitive compound to form photosensitive aggregates, and then nanoparticles may be combined with the aggregates to form the microcapsules. The shell may be composed of nanoparticles and/or polymer, and the core interior may contain the photosensitive compound. Formation occurs rapidly (on the order of seconds) and the conditions are very mild (at room temperature, in aqueous solution, and at neutral pH). The microcapsule synthesis is highly suitable as an encapsulation method, particularly for a charged photosensitive molecule like ICG.