Hydrophilic Cu₉S₅ Nanocrystals: A Photothermal Agent with a 25.7% Heat Conversion Efficiency for Photothermal Ablation of Cancer Cells in Vivo

Abstract

Photothermal ablation (PTA) therapy has a great potential to revolutionize conventional therapeutic approaches for cancers, but it has been limited by difficulties in obtaining biocompatible photothermal agents that have low cost, small size (<100 nm), and high photothermal conversion efficiency. Herein, we have developed hydrophilic plate-like Cu(9)S(5) nanocrystals (NCs, a mean size of ∼70 nm × 13 nm) as a new photothermal agent, which are synthesized by combining a thermal decomposition and ligand exchange route. The aqueous dispersion of as-synthesized Cu(9)S(5) NCs exhibits an enhanced absorption (e.g., ∼1.2 × 10(9) M(-1) cm(-1) at 980 nm) with the increase of wavelength in near-infrared (NIR) region, which should be attributed to localized surface plasmon resonances (SPR) arising from p-type carriers. The exposure of the aqueous dispersion of Cu(9)S(5) NCs (40 ppm) to 980 nm laser with a power density of 0.51 W/cm(2) can elevate its temperature by 15.1 °C in 7 min; a 980 nm laser heat conversion efficiency reaches as high as 25.7%, which is higher than that of the as-synthesized Au nanorods (23.7% from 980 nm laser) and the recently reported Cu(2-x)Se NCs (22% from 808 nm laser). Importantly, under the irradiation of 980 nm laser with the conservative and safe power density over a short period (∼10 min), cancer cells in vivo can be efficiently killed by the photothermal effects of the Cu(9)S(5) NCs. The present finding demonstrates the promising application of the Cu(9)S(5) NCs as an ideal photothermal agent in the PTA of in vivo tumor tissues.

A Novel Photothermal Nanocrystals of Cu7S4 Hollow Structurefor Efficient Ablation of Cancer Cells

“…4. Specifically, the Cu 7 S 4 NCs exhibit a minimum of absorption around ∼670 nm and an increased absorption with the increase of wavelength with the maximum absorption peak of ∼1100 nm, in analogy to the reported Cu 2-x S [19,24]. This stronger absorption in NIR region of Cu 7 S 4 NCs prepared by injecting sulfide source makes them a potential 980 nm-laser-driven photothermal agents for ablation of cancer cells.…”

“…Alternatively, copper-containing semiconductor nanocrystals, characterized by low production cost, high stability, low toxicity, and high photothermal conver-sion efficiency, provide promising platforms as photothermal agents [19][20][21][22][23]. CuS nanoparticles [24], CuS superstructures [21], Cu 9 S 5 nanocrystals [19], and Fe 3 O 4 @Cu 2−x S [22], Cu 9 S 5 @SiO 2 [20] nanocomposites have been developed as 980 nm laser-driven photothermal agents for efficient PTA of cancer cells in vitro and in vivo. To meet the severe requirements of future PTA therapy, it is still necessary to develop novel kind of copper chalcogenides based photothermal agents.…”

Copper sulfide nanoparticles: from synthesis to biomedical applications

“…Several CuS nanostructures are reported as excellent transducer agents for photothermal therapy, including the CuS flower-like superstructures [53] with the mean size of ~1 μm and CuS plate-like nanocrystals [10] with a mean size of ~70 nm×13 nm ( Figure 5). These CuS NPs exhibit strong absorbance and conversion efficiency upon 980 nm laser irradiation, leading to a higher local temperature to kill the cancer cells.…”

Nondestructive rubbing fabrication of flexible graphene film for precise temperature controlling

“…A number of materials, with high optical absorbance in the NIR region, have been developed for laserinduced heat, including plasma nanostructure, carbon-based material, and the other novel inorganic materials. [15][16][17][18][19][20] The ultrahigh flexibility, high thermal conductivity 21 and thermal stability of graphene inspired us to imagine that significant progress could be made for the utilization of graphene film as the suitable candidate for thin film heater. [22][23][24][25][26][27] The flexible graphene film present an extremely rapid temperature response and maintain an excellent photothermal conversion stability by remote nearinfrared laser irradiation.…”