Direct deposition of anatase TiO2 on thermally unstable gold nanobipyramid: Morphology-conserved plasmonic nanohybrid for combinational photothermal and photocatalytic cancer therapy

Deposition of crystalline titanium dioxide (TiO2) on gold nanostructures has been considered as a promising strategy for near-infrared (NIR) light-activated photocatalysis. A typical route comprises pre-deposition of amorphous TiO2 on the gold surface and its ensuing crystallization by high-temperature annealing. Such condition, however, is not compatible with highly plasmonic but thermally unstable sharp-tipped gold nanostructures, causing structural disruption and plasmonic decline. Herein, we report a hybridization method excluding high-temperature annealing, i.e., direct deposition of anatase TiO2 onto sharp-tipped gold nanobipyramid (Au NBP/a-TiO2) with conserving their morphology without agglomeration via low-temperature hydrothermal reaction. In addition to keeping the plasmonic photothermal performance, Au NBP/a-TiO2 exhibits enhanced photocatalytic generation of reactive oxygen species in response to the NIR excitation, evidencing the efficient injection of hot electrons from the Au NBP to the anatase shell. In vitro and in vivo studies revealed that the efficient photocatalytic/photothermal responses of Au NBP/a-TiO2, along with dispersion stability in biological media and minimal toxicity, hold potential for synergistic photothermal and photodynamic therapy. We believe that the low-temperature synthetic method introduced here might offer a general way of crystalline deposition of TiO2 on a variety of gold nanostructures, broadening the spectrum of NIR-responsive photocatalytic hybrid nanostructures for biomedical applications

Palladium nanoparticles decorated MXene for plasmon-enhanced photocatalysis

Two-dimensional MXene nanomaterials have found a wide application range in recent years. Here, Ti3C2 MXene nanosheets exhibiting inherent photothermal activity reveal synergistic plasmon-enhanced photocatalytic properties upon rational surface decoration with palladium nanoparticles (NPs). Pd incorporation induces a 1.7-fold increase in the number of defect sites on the MXene surface. Most importantly, the introduced Pd nanoparticles favour an effective separation and collection of localized surface plasmon resonance (LSPR)-induced hot charge carriers generated at the surface of semi-metallic Ti3C2 NS, further facilitating the generation of hydrogen peroxide (H2O2). The generated H2O2 is sequentially decomposed to hydroxyl radicals via the peroxidase (POD)-like activity of Pd NPs. The Pd@MXene shows approximately 2-fold enhancement of photocatalytic activity and excellent photostability under laser irradiation. Taken together, this study highlights the promise of constructing active and stable MXene-based nanohybrids for highly effective photo-responsive nanomedicine

Sophisticated plasmon-enhanced photo-nanozyme for anti-angiogenic and tumor-microenvironment-responsive combinatorial photodynamic and photothermal cancer therapy

In the exploitation of nanozymes possessing intrinsic enzyme-like activities for cancer therapy, minor focus has been devoted to plasmonic nanostructures with localized surface plasmon resonance (LSPR)-driven properties. Here, we report the application of unique peroxidase-mimicking plasmonic photo-nanozymes coupling tumor-microenvironment-responsive reactive oxygen species generation with photothermal effect for effective combinatorial therapy. The well-defined anisotropic photo-nanozyme is synthesized by selectively depositing Pd nanoparticles on the tips of gold nanobypyramids. Intrinsic peroxidase-like properties with 1.5-fold-activity enhancement under photoexcitation are ascribed to a Pd-induced hot electrons/holes separation with efficient H2O2 decomposition. The LSPR-induced photocatalytic/photothermal combinatorial effects are remarkably enhanced upon H2O2 addition, critically suppressing the cell survival rate under near-infrared light. An effective decomposition of cell-signaling H2O2 additionally reveals prominent expression hindrance of vascular endothelial growth factor and hypoxia-inducible factor 1α. Our seminal findings uncover an interrelation between LSPR-induced phenomena and biomimetic fingerprints, valuable to overcome the shortcomings of conventional photodynamic therapy

Plasmon-Triggered Upconversion Emissions and Hot Carrier Injection for Combinatorial Photothermal and Photodynamic Cancer Therapy

Despite the unique ability of lanthanide-doped upconversion nanoparticles (UCNPs) to convert near-infrared (NIR) light to high-energy UV–vis radiation, low quantum efficiency has rendered their application unpractical in biomedical fields. Here, we report anatase titania-coated plasmonic gold nanorods decorated with UCNPs (Au NR@aTiO2@UCNPs) for combinational photothermal and photodynamic therapy to treat cancer. Our novel architecture employs the incorporation of an anatase titanium dioxide (aTiO2) photosensitizer as a spacer and exploits the localized surface plasmon resonance (LSPR) properties of the Au core. The LSPR-derived near-field enhancement induces a threefold boost of upconversion emissions, which are re-absorbed by neighboring aTiO2 and Au nanocomponents. Photocatalytic experiments strongly infer that LSPR-induced hot electrons are injected into the conduction band of aTiO2, generating reactive oxygen species. As phototherapeutic agents, our hybrid nanostructures show remarkable in vitro anticancer effect under NIR light [28.0% cancer cell viability against Au NR@aTiO2 (77.3%) and UCNP@aTiO2 (98.8%)] ascribed to the efficient radical formation and LSPR-induced heat generation, with cancer cell death primarily following an apoptotic pathway. In vivo animal studies further confirm the tumor suppression ability of Au NR@aTiO2@UCNPs through combinatorial photothermal and photodynamic effect. Our hybrid nanomaterials emerge as excellent multifunctional phototherapy agents, providing a valuable addition to light-triggered cancer treatments in deep tissue