Encapsulation of a Phase‐Change Material in Nanocapsules with a Well‐Defined Hole in the Wall for the Controlled Release of Drugs

: As a class of biocompatible and biodegradable phase-change materials, natural fatty acids have received considerable interest in recent years for temperature-controlled release of drugs. However, the poor dispersibility and colloidal stability of their nanoparticles under physiological conditions place a major limitation on their applications in biomedicine. Herein, we report a facile method for encapsulating a mixture of two natural fatty acids (with a eutectic melting point at 39 °C) in a biocompatible, silica-based nanocapsule to achieve both stable dispersion and controllable release of drugs. The nanocapsules have a well-defined hole in the wall to ensure easy loading of fatty acids, together with multiple types of functional components such as therapeutics and near-infrared dyes. The payloads can be released through the hole when the fatty acids are melted upon photothermal heating. The release profile can be controlled by varying the size of the hole and/or the duration of laser irradiation.