Palladium Nanocapsules for Photothermal Therapy in the Near-Infrared II Biological Window

Abstract

Recent developments in nanomaterials with programmable optical responses and their capacity to modulate the photothermal effect induced by an extrinsic source of light have elevated plasmonic photothermal therapy (PPTT) to the status of a favored treatment for a variety of malignancies. However, the low penetration depth of nearinfrared-I (NIR-I) lights and the need to expose the human body to a high laser power density in PPTT have restricted its clinical translation for cancer therapy. Most nanostructures reported to date exhibit limited performance due to (i) activity only in the NIR-I region, (ii) the use of intense laser, (iii) need of large concentration of nanomaterials, or (iv) prolonged exposure times to achieve the optimal hyperthermia state for cancer phototherapy. To overcome these shortcomings in plasmonic nanomaterials, we report a bimetallic palladium nanocapsule (Pd Ncap)�with a solid gold bead as its core and a thin, perforated palladium shell�with extinction both in the NIR-I as well as the NIR-II region for PPTT applications toward cancer therapy. The Pd Ncap demonstrated exceptional photothermal stability with a photothermal conversion efficiency of ∼49% at the NIR-II (1064 nm) wavelength region at a very low laser power density of 0.5 W/cm 2 . The nanocapsules were further surfacefunctionalized with Herceptin (Pd Ncap-Her) to target the breast cancer cell line SK-BR-3 and exploited for in vitro PPTT applications using NIR-II light. Pd Ncap-Her caused more than 98% cell death at a concentration of just 50 μg/mL and a laser power density of 0.5 W/cm 2 with an output power of only 100 mW. Flow cytometric and microscopic analyses revealed that Pd Ncap-Herinduced apoptosis in the treated cancer cells during PPTT. Additionally, Pd Ncaps were found to have reactive oxygen species (ROS) scavenging ability, which can potentially reduce the damage to cells or tissues from ROS produced during PPTT. Also, Pd Ncap demonstrated excellent in vivo biocompatibility and was highly efficient in photothermally ablating tumors in mice. With a high photothermal conversion and killing efficiency at very low nanoparticle concentrations and laser power densities, the current nanostructure can operate as an effective phototherapeutic agent for the treatment of different cancers with ROS-protecting ability.

Noble Metal Nanoparticle-Based Photothermal Therapy: Development and Application in Effective Cancer Therapy

“…This property facilitates photothermal–electronic interactions, leading to the generation of heat capable of ablating tumor cells. Prem Singh et al [ 90 ] investigated the synthesis of innovative bimetallic palladium nanocapsules (Pd Ncap), comprising gold bead cores encased within hollow porous palladium shells, and explored their application in the realm of photothermal therapy for cancer therapy. The researchers employed bifunctional carboxy-PEG-thiols as junctions and functionalized Pd Ncaps with the targeting molecule Herceptin to enhance the targeting efficacy against SK-BR-3 cells.…”

Cationic dextrin nanoparticles for effective intracellular delivery of cytochrome C in cancer therapy

“…1,2 For several years, researchers have been engaged in developing suitable and less toxic mediated therapies as an alternative to conventional chemotherapy and radiation therapy to combat the associated risks to healthy cells. 3–5 The development of nanotechnology has led to the emergence of various anticancer treatment methods, 6–9 among which therapeutic protein delivery has been deemed of utmost importance in recent times. This is because, unlike chemotherapy where the anticancer drugs are not specific to the cancer tissue and damage healthy cells, and drug resistance develops upon repeated administration, 10 a therapeutic protein offers increased specificity, selectivity, and reduced toxicity towards healthy cells.…”

Highly efficient NIR-II photothermal conversion from a 2,2′-biquinoline-4,4′-dicarboxylate-based photochromic complex

“…11 In this context, significant efforts have been dedicated to exploring NIR-II absorbing photothermal agents. Various inorganic materials, including non-metallic materials, 12 noble metals 13,14 and transition metals, 15 as well as organics, such as organic small molecules, 16,17 covalent organic frameworks (COFs), 18 hydrogen-bonded organic frameworks (HOFs), 19 and polymers, 20 have been demonstrated as promising candidates for NIR-II photothermal conversion (Table S1 †). Among them, there has been a recent surge in studies on NIR-II photothermal agents based on small organic molecules, as their superior photothermal efficiency enables the achievement of higher temperatures with lower input NIR laser power densities, a crucial aspect for practical applications.…”