Rationally designed dual-plasmonic gold nanorod@cuprous selenide hybrid heterostructures by regioselective overgrowth for in vivo photothermal tumor ablation in the second near-infrared biowindow

NIR-II plasmonic materials offer multiple functionalities for in vivo biomedical applications, such as photothermal tumor ablation, surface-enhanced Raman scattering biosensing, photoacoustic imaging, and drug carriers. However, integration of noble metals and plasmonic semiconductors is greatly challenging because of the large lattice-mismatch. This study reports the regioselective overgrowth of Cu(2-x)Se on gold nanorods (GNRs) for preparation of dual-plasmonic GNR@Cu(2-x)Se hybrid heterostructures with tunable NIR-II plasmon resonance absorption for in vivo photothermal tumor ablation. Methods: The regioselective deposition of amorphous Se and its subsequent conversion into Cu(2-x)Se on the GNRs are performed by altering capping agents to produce the GNR@Cu(2-x)Se heterostructures of various morphologies. Their photothermal performances for NIR-II photothermal tumor ablation are evaluated both in vitro and in vivo. Results: We find that the lateral one- and two-side deposition, conformal core-shell coating and island growth of Cu(2-x)Se on the GNRs can be achieved using different capping agents. The Cu(2-x)Se domain size in these hybrids can be effectively adjusted by the SeO(2) concentration, thereby tuning the NIR-II plasmon bands. A photothermal conversion efficiency up to 58-85% and superior photostability of these dual-plasmonic hybrids can be achieved under the NIR-II laser. Results also show that the photothermal conversion efficiency is dependent on the proportion of optical absorption converted into heat; however, the temperature rise is tightly related to the concentration of their constituents. The excellent NIR-II photothermal effect is further verified in the following in vitro and in vivo experiments. Conclusions: This study achieves one-side or two-side deposition, conformal core-shell coating, and island deposition of Cu(2-x)Se on GNRs for GNR@Cu(2-x)Se heterostructures with NIR-II plasmonic absorption, and further demonstrates their excellent NIR-II photothermal tumor ablation in vivo. This study provides a promising strategy for the rational design of NIR-II dual-plasmonic heterostructures and highlights their therapeutic in vivo potential.