PMC

a, A plot of the concentrations of lysozyme released from the Au nanocages upon heating at 37 °C for different periods of time. b, Lysozyme bioactivity test. Linear fit (y: absorbance, x: time) for native lysozyme: y = −0.01432x + 0.3441, R² = 0.9964 and linear fit for the released lysozyme: y = −0.01124x + 0.2961, R² = 0.9966.

Absorption spectra of alizarin-PEG released from the copolymer-covered Au nanocages a, by heating at 42 °C for 1, 3, 5, and 10 min; b, by exposure to a pulsed NIR laser at a power density of 10 mW/cm² for 1, 2, 4, 8, and 16 min; and c, by exposure to the NIR laser for 2 min at 10, 25, and 40 mW/cm². The insets show the concentrations of alizarin-PEG released from the nanocages under different conditions.

a, A plot of the concentrations of Dox released from the Au nanocages upon heating at 45 °C for different periods of time. b, Cell viability for samples after going through different treatments: (C-1) cells irradiated with a pulsed NIR laser for 2 min in the absence of Au nanocages; (C-2) cells irradiated with the laser for 2 min in the presence of Dox-free Au nanocages; and (2/5 min) cells irradiated with the laser for 2 and 5 min in the presence of Dox-loaded Au nanocages. A power density of 20 mW/cm² was employed for all these studies.

a, Schematic illustrating how the system works. A side view of the Au nanocage is used for the illustration. Upon exposure to a NIR laser, the light is absorbed by the nanocage and converted into heat, triggering the smart polymer to collapse and thus release the pre-loaded effector. When the laser is turned off, the polymer chains will relax back to the extended confrmation and terminate the release. b, Atom transfer radical polymerization of NIPAAm and AAm monomers (at a molar ratio of m/n) as initiated by a disulfide initiator and in the presence of a Cu(I) catalyst. c, TEM images of Au nanocages whose surface was covered by a pNIPAAm-co-pAAm copolymer with an LSCT at 39 °C. The inset shows a magnified TEM image of the corner of such a nanocage.