Broadband and Spectrally Selective Photothermal Conversion through Nanocluster Assembly of Disordered Plasmonic Metasurfaces

Plasmonic metasurfaces have been realized for efficient light absorption, thereby leading to photothermal conversion through nonradiative decay of plasmonic modes. However, current plasmonic metasurfaces suffer from inaccessible spectral ranges, costly and time-consuming nanolithographic top-down techniques for fabrication, and difficulty of scale-up. Here, we demonstrate a new type of disordered metasurface created by densely packing plasmonic nanoclusters of ultrasmall size on a planar optical cavity. The system either operates as a broadband absorber or offers a reconfigurable absorption band right across the visible region, resulting in continuous wavelength-tunable photothermal conversion. We further present a method to measure the temperature of plasmonic metasurfaces via surface-enhanced Raman spectroscopy (SERS), by incorporating single-walled carbon nanotubes (SWCNTs) as an SERS probe within the metasurfaces. Our disordered plasmonic system, generated by a bottom-up process, offers excellent performance and compatibility with efficient photothermal conversion. Moreover, it also provides a novel platform for various hot-electron and energy-harvesting functionalities.

In Situ Formation of Nanotheranostics to Overcome the Blood-Brain Barrier and Enhance Treatment of Orthotopic Glioma

Glioblastoma is one of the most lethal cancers and needs effective therapeutics. The development of coordination-driven metal-organic nanoassemblies, which can cross the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) and have multiple desired functions, may provide a promising solution to this issue. Here, we report an in situ assembled nanoplatform based on RGD peptide-modified bisulfite-zinc^II-dipicolylamine-Arg-Gly-Asp (Bis(DPA-Zn)-RGD) and ultrasmall Au-ICG nanoparticles. Attributed to its positive charges and neovascular targeting properties, Bis(DPA-Zn)-RGD can be selectively delivered to the tumor site, and then assembled in situ into large nanoclusters with subsequently administered Au-ICG nanoparticles. Au nanoparticles with ultrasmall size (∼7 nm) can successfully cross the BBB. The obtained nanoclusters exhibit strong near-infrared-red (NIR) absorption and an enhanced tumor retention effect, enabling precise orthotopic fluorescence/photoacoustic imaging. With the aid of image guidance, the photothermal effect of the nanoclusters is observed to suppress tumor progression with the inhibition efficiency reaching up to 93.9%. Meanwhile, no photothermal damage can be found for normal brain tissues. These results, herein, suggest a feasible nanotheranostic agent with the ability to overcome the BBB and BBTB for imaging and therapy of orthotopic brain tumors.