NIR-Responsive Gold Nanorod Capsules for Efficient Cargo Encapsulation and Release

Gold nanoparticle-based vesicular nanostructures are attractive drug delivery platforms because of their tunable plasmonic properties; however, simultaneously achieving efficient cargo encapsulation, robust aqueous stability, and controllable near-infrared (NIR)-triggered release remains challenging. Herein, water-dispersible and NIR-responsive gold nanorod capsules (Au NrCs) are fabricated from mini-gold nanorods (mini-Au NRs) and small amphiphilic hexaethylene glycol (EG6) ligands via a solute-induced phase separation strategy. Owing to their compact dimensions and tunable longitudinal localized surface plasmon resonance, the mini-Au NRs enable assembly within sub-200 nm nanocapsules while retaining NIR responsiveness. During capsule formation, nanoparticles and DNA cargoes are simultaneously encapsulated and concentrated within the capsules through liquid-liquid phase separation, achieving approximately 90% DNA encapsulation efficiency and more than 1000-fold enrichment. Furthermore, amino-terminated EG6 ligands enable post-assembly crosslinking of the Au NrCs with diepoxy-polyethylene glycol, improving aqueous stability and dispersibility. The resulting Au NrCs exhibit efficient cargo release (>95% within a few minutes) under low-power 810 nm NIR LED irradiation through capsule disassembly, highlighting the potential of plasmonic nanocapsules for externally controlled delivery under relatively mild NIR LED irradiation conditions. These results establish a plasmonic nanocarrier platform integrating concentration-assisted cargo encapsulation, enhanced aqueous stability, and controllable NIR-triggered release, providing a basis for future drug delivery applications.