nanocages

Nanocages are nanoscale hollow structures with a cavity enclosed by a permeable shell. They can be composed of metals, silica, polymers, or hybrid materials. The defining feature is the hollow interior and a porous or tunable shell that allows encapsulation of cargo while permitting diffusion of small molecules.

Gold, silver, and other noble metal nanocages are among the most studied examples, often produced by templating metal nanocubes and applying galvanic replacement to create porous walls. Silica and polymeric nanocages are also widely used, formed by template methods or self-assembly, allowing precise control over cavity size, shell thickness, and porosity. Functionalization of the outer surface with ligands, antibodies, or polymers enables targeting and stabilization in biological environments. The optical, catalytic, and magnetic properties of nanocages can be tuned by adjusting size, composition, and shell thickness, making them suitable for imaging, sensing, and therapy.

Applications include drug and gene delivery, where payloads are protected inside the cavity and released in response to stimuli; photothermal therapy using plasmonic nanocages that convert light to heat; and biomedical imaging as contrast agents. Challenges include potential toxicity, stability in physiological conditions, and the need for scalable, reproducible manufacturing, as well as clearance and long-term safety in vivo. Research continues to improve design principles and expand applications.