Au Nanoshells Research Articles

The Multifunctionally Graded System for a Controlled Size Effect on Iron Oxide-Gold Based Core-Shell Nanoparticles.

We report that Fe3O4@Au core-shell nanoparticles (NPs) serve as a multifunctional molecule delivery platform. This platform is also suitable for sensing the doxorubicin (DOX) through DNA hybridization, and the amount of carried DOX molecules was determined by size-dependent Fe3O4@Au NPs. The limits of detection (LODs) for DOX was found to be 1.839 nM. In our approach, an Au nano-shell coating was coupled with a specially designed DNA sequence using thiol bonding. By means of a high-frequency magnetic field (HFMF), a high release percentage of such a molecule could be efficiently achieved in a relatively short period of time. Furthermore, the thickness increase of the Au nano-shell affords Fe3O4@Au NPs with a larger surface area and a smaller temperature increment due to shielding effects from magnetic field. The change of magnetic property may enable the developed Fe3O4@Au-dsDNA/DOX NPs to be used as future nanocarrier material. More importantly, the core-shell NP structures were demonstrated to act as a controllable and efficient factor for molecule delivery.

Photoactivated nanomotors via aggregation induced emission for enhanced phototherapy

Aggregation-induced emission (AIE) has, since its discovery, become a valuable tool in the field of nanoscience. AIEgenic molecules, which display highly stable fluorescence in an assembled state, have applications in various biomedical fields—including photodynamic therapy. Engineering structure-inherent, AIEgenic nanomaterials with motile properties is, however, still an unexplored frontier in the evolution of this potent technology. Here, we present phototactic/phototherapeutic nanomotors where biodegradable block copolymers decorated with AIE motifs can transduce radiant energy into motion and enhance thermophoretic motility driven by an asymmetric Au nanoshell. The hybrid nanomotors can harness two photon near-infrared radiation, triggering autonomous propulsion and simultaneous phototherapeutic generation of reactive oxygen species. The potential of these nanomotors to be applied in photodynamic therapy is demonstrated in vitro, where near-infrared light directed motion and reactive oxygen species induction synergistically enhance efficacy with a high level of spatial control.

Bioinspired protein corona strategy enhanced biocompatibility of Ag-Hybrid hollow Au nanoshells for surface-enhanced Raman scattering imaging and on-demand activation tumor-phototherapy

Silver-based hybrid nanoprobes for surface-enhanced Raman scattering (SERS) imaging show their tremendous potential for precise biological detection and mediated phototherapy. However, the severe toxicity induced by Ag to normal mammalian cells hinders its further application. Herein, we presented a versatile bioinspired protein corona strategy through assembling bovine serum albumin (BSA) protected Raman tag DTTC-conjugated Ag-hybrid hollow Au nanoshells (hollow AgAu-DTTC-BSA), which their silver ion release and reactive oxygen species (ROS) generation are significantly suppressed, enabling no damage to normal cells and tissues, but can be reactivated on-demand under laser-irradiation at the tumor site. These nanoshells could also produce strong localized surface plasmon resonance for efficient-stable photothermal effect and enhanced SERS activity under laser irradiation, approved by both theoretical and experimental calculations. Furthermore, the biocompatible hollow AgAu-DTTC-BSA could detect both primary tumor tissues and tiny liver metastases (~0.18 mm) in orthotopic/subcutaneous CT26 colon tumor-bearing mice models. We also demonstrate their excellent therapeutic efficacy for colorectal solid neoplasms by accurate SERS imaging-guided photothermal therapy, simultaneously assisted with toxic Ag ion and ROS. These results suggest that hollow AgAu-DTTC-BSA is promising imaging assisted photothermal agents for solid tumor theranostics and enhancing the potential of Ag-based nanoparticles for practical treatment.

Catalase-like nanosystem for interlocking trimodal cancer therapy with hypoxia relief

Hypoxia is a hallmark of solid tumors, and it significantly impairs the overall anticancer efficacy, particularly photodynamic therapy (PDT). Herein, a catalase-like nanovesicle with near-infrared light-responsiveness, that is, platinum/gold nanoshell encapsulated chlorin e6 (Ce6)/resveratrol (Res) liposome (Pt@Au-Ce6/Res-Lip), was developed to surmount this intractable issue. The Pt@Au-Ce6/Res-Lip can decompose overexpressed H2O2 in tumor microenvironment to produce vast amounts of O2 for further enhancement of the PDT. Under the 808 nm laser irradiation, the Au nanoshells induced hyperthermia at the lesion site to ablate tumor cells, simultaneously inducing the controlled release of photosensitizer Ce6 and chemotherapeutic agent Res. Moreover, stimulated by 660 nm laser, numerous reactive oxygen species were formed to induce apoptosis and necrosis of tumor cells. With the cascade of trimodal therapeutic modality options (chemotherapy, photothermal therapy, and PDT), the Pt@Au-Ce6/Res-Lip showed ultrahigh tumor inhabitation rate in in vitro and in vivo studies, signifying that the Pt@Au-Ce6/Res-Lip nanovesicle is a promising candidate for effective cancer therapy.

Magnetically Tunable Plasmon Coupling of Au Nanoshells Enabled by Space-Free Confined Growth.

We report the unconventional space-free confined growth of Au nanoshells with well-defined plasmonic properties and active tuning of their plasmon coupling by the nanoscale magnetic assembly. The seeded growth of Au exclusively occurred at the hard-soft interfaces between the Fe3O4 core and phenolic resin without the need of creating a limiting space, which represents a general and elegant approach to various core-shell nanostructures. The deformability of permeable phenolic layers plays an essential role in regulating the interfacial growth of Au nanoshells. While the polymer elasticity suppresses the radial deposition of Au atoms, their high deformability can afford enough spaces for the formation of conformal metallic shells. The coupled magnetic-plasmonic properties allow active tuning of the plasmon coupling and the resonant scattering of Au nanoshells by the magnetic assembly of the hybrid nanoparticles into plasmonic chains, whose potentials in applications have been demonstrated in designing transparent displays and anticounterfeiting devices.

Application of Gold-Based Nanomaterials in Tumor Photothermal Therapy and Chemotherapy.

Photothermal therapy (PTT) is a minimally invasive tumor treatment method in which photothermal conversion agents (PTAs) can be enriched in tumor tissue by external light stimulation to convert photon energy into thermal energy to induce the temperature of tumor tissue higher than normal physiological, and can effectively kill tumor cells and tissues while avoiding damage to healthy tissue. As a well-known biocompatible nanomaterial, gold-based nanomaterials have high photothermal conversion efficiency and cross section, which can be used in tumor targeting therapy treatment as a potential photothermal conversion agent. Combining PTT and chemotherapy can be achieved by loading a chemotherapeutic drug modified on the surface of a gold nanomaterials. Therefore, this paper first reviews the preparation and surface functionalization of Au-based nanomaterials, such as Au nanorods, Au nanostars, Au nanoshells, and so on. Second, we have also introduced the application of Au-based nanomaterials in PTT, chemotherapy, and combination therapy. Finally, the limitations and challenges of Au-based photothermal conversion agents are summarized and the development prospects in this field are prospected.

Facile synthesis of porous hollow Au nanoshells with enhanced catalytic properties towards reduction of p-nitrophenol

We presented a facile synthesis of porous hollow Au nanoshells (PHASs) with excellent catalytic properties by galvanic replacement and dealloying process. The addition amount of HAuCl4 during galvanic replacement played the important role in controlling structure, catalytic and optical properties of PHASs. The PHASs exhibited shorter induction time and highly catalytic rate constant towards reduction of p-nitrophenol by NaBH4. The catalytic rate constant of PHASs (17.2 × 10−3 s−1) was 25 times that of sacrificial Ag particles, 4.2 times that of Ag@Au with dense Au shell and 1.5 times that of Ag-Au alloys at same particle concentration. The normalized rate constant of PHASs (143 s-1 mmol−1) was 5.3 times that of Ag@Au and 1.6 times that of Ag-Au alloys. The as-synthesized PHASs with unique structures and tunable properties have fantastic potential applications in catalysis, biosensors, drug delivery and cancer therapy.

A hollow-structured nanohybrid: Intelligent and visible drug delivery and photothermal therapy for cancer

It is of great valuable in drug delivery to fabricate multifunctional nanovehicle for cancer therapy. Herein, hollow-structured hCu2-xS@Au nanoshell/satellite composite with doxorubicin-carrying was designed and synthesized for intelligent and visible drug delivery and satisfactory photothermal therapy. By modification of disulfide linkage bridged Au nanoshell and multi-carboxylic graphene quantum dots (MC-GODs) on the surface of hCu2-xS@Au nanoparticles, both the high concentration of glutathione and low pH in cancer cell/tissue can induce responsive drug release. The satisfactory photothermal conversion efficiency (32%) of hCu2-xS@Au@MC-GODs under 808 nm near-infrared (NIR) laser irradiation ascribed to the reduced bandgap and more circuit paths for electron transitions for hCuS modified with Au nanoparticles depend on density functional theory, which antitumor therapy efficacy was greatly enhanced by combining chemo- and photothermal therapy. Moreover, the fluorescence of MC-GODs was quenched/“turn off” as linking to the surface of hCu2-xS@Au, and also restored/“turn on” as the MC-GODs detaching from the surface of hCu2-xS@Au. The fluorescent switch of MC-GODs can serve as both a controllable drug release “guard” and “eyes” for visualized monitoring. The multi-modality therapy with controllable drug delivery, visual monitoring and high photothermal conversion efficiency may be anticipated by this versatile strategy.

A Dual-Amplification Electrochemical Aptasensor for Profenofos Detection

The present study reported a dual-amplification electrochemical aptasensor for sensitive detection of profenofos (PFF) in vegetables. A screen-printed carbon electrode (SPCE) modified with graphitized multi-walled carbon nanotubes (MWCNTGr) and Au nanoshell was used as a test platform, which ensured a rapid detection process and showed a favorable electrochemical performance. MWCNTGr and Au nanoshell enhanced the electrical conductivity and the surface area, thus the detection signal was amplified. The affinity between PFF and its aptamer (Apt) was verified firstly by dot blot hybridization (DBH), and the result was exciting. Furthermore, the effects of the aptamers modified respectively with -NH2 and -SH on the current signal were compared with each other by cyclic voltammetry (CV), and results showed that the aptamers modified with -NH2 made the current signal change more obvious. Based on all above, a high-efficiency electrochemical aptasensor was fabricated with a wide linear range from 0.1–1 × 105 ng · ml−1 and a detection limit of 0.052 ng · ml−1 under the optimized conditions. This aptasensor had great specificity, stability and reproducibility. Hence, the developed aptasensor was successfully used to detect PFF in vegetables. The proposed method also has a potential for the detection of other organophosphorus pesticide (OPs).

High quality factor D-type fiber surface plasmon resonance (SPR) sensor based on the modification of gold nanoshells

A D-type optical fiber surface plasmon resonance (SPR) sensor based on gold film and Au nanoshells is described. The sensor has a smaller full width at half maximum (FWHM) and a higher quality factor. The influence of the coupling effect between the Au nanoshells and gold film with different internal and external diameter ratios on the sensor was investigated by the finite element method. The simulation results show that the coupling effect between the SPR of the gold film and the localized surface plasmon resonance (LSPR) of the Au nanoshells effectively improved the electric field strength of the sensing region. The refractive index measurements show that the sensitivity of the D-type fiber/gold film/Au nanoshell (50/40 AuNS) SPR sensor is 3064 nm/RIU, which is 993 nm/RIU higher than for the D-type fiber/gold film SPR sensor. The D-type fiber/gold film/Au nanoshell (50/40 AuNS) SPR sensor also provides good linearity with a value of 99.4%. The sensor reported in this paper can be used for reference in the development of high performance biosensors.

Super-efficient laser hyperthermia of malignant cells with core-shell nanoparticles based on alternative plasmonic materials

New type of highly absorbing core-shell AZO/Au (aluminum doped zinc oxide/gold) and GZO/Au (gallium doped zinc oxide/gold) nanoparticles have been proposed for hyperthermia of malignant cells purposes. Comparative studies of pulsed laser hyperthermia were performed for Au nanoshells with AZO core and traditional SiO2 (quartz) core. We show that under the same conditions, the hyperthermia efficiency in the case of AZO increases by several orders of magnitude compared to SiO2 due to low heat capacity of AZO. Similar results have been obtained for GZO core which has same heat capacity. Calculations for pico-, nano- and sub-microsecond pulses demonstrate that reduced pulse duration results in strong spatial localization of overheated areas around nanoparticles, which ensures the absence of negative effects to the normal tissue. Moreover, we propose new alternative way for the optimization of hyperthermia efficiency: instead of maximizing the absorption of nanoparticles, we enhance the thermal damage effect on the membrane of malignant cell. This strategy allows to find the parameters of nanoparticle and the incident radiation for the most effective therapy.

Synthesis and Catalytic Activities of Metal Shells (Monolayer, Bilayer, and Alloy Layer)-Coated Gold Octahedra toward Catalytic Reduction of Nitroaromatics

Different types of metal shells such as monolayer, bilayer, and alloy layer of gold (Au) and/or silver (Ag) on gold octahedra (AuOh) nanoparticles were synthesized using N-[3-(trimethoxysilyl)propyl]diethylenetriamine (TPDT) without employing any external reducing agents. TPDT, an alternative to sodium borohydride, was used to prepare 15 different core–shell metal nanostructures. The direct colloidal synthesis and stabilization of silver octahedra nanoparticles is still a challenging task. The proposed methodology is an alternative synthetic route for Ag or Au nanoshell coated onto the AuOh core. UV–vis absorption spectroscopy, high-resolution electron transmission microscopy analyses with selected area electron diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, and X-ray diffraction techniques were used to characterize the prepared core–shell octahedra nanostructures. High-angle annular dark field scanning transmission electron microscopy–energy-dispersive X-...

Combined chemo/photothermal therapy based on mesoporous silica-Au core-shell nanoparticles for hepatocellular carcinoma treatment

Chemotherapy has been widely used for treatment to malignant cancer, such as hepatocellular carcinoma (HCC). Chemotherapeutic effect was not often efficient to achieve totally tumor ablation due to the poor cellular uptake and drug resistance. To address these problems, a novel nanoplatform was constructed based on nontoxic mesoporous silica nanoparticles (MSNs) for a combined chemo/photothermal therapy to enhance tumor cell accumulation and promote toxicity of chemotherapeutic drugs. Prepared MSNs were consisted of Au nanoshell for photothermal conversion and a first-line anti-HCC drug-sorafenib (SO) for chemotherapy. The SO-Au-MSNs could help SO accumulate more in hepatic cancer cells. Under near infrared irradiation, SO-Au-MSNs exerted a high cell inhibition rate which could be attributed to the enhanced toxicity of SO under hyperthermia and synergistic chemo/photothermal therapy. SO-Au-MSNs showed a good compatibility as well as efficient cell cytotoxicity. Overall, SO-Au-MSNs would be a promising candidate for further enhancing the antitumor effect on HCC.

Ionic Liquid-in-Water Emulsion-templated Synthesis of Gold Nanoshells at the Liquid-Liquid Interface between Water and Primary Ammonium-based Ionic Liquids

Au nanoshells have been synthesized at the liquid-liquid interface between primary ammonium-based ionic liquids and water. Ionic liquid-in-water emulsions, which are spontaneously formed on the wat...

Correction to “Angle- and Momentum-Resolved Photoelectron Velocity Map Imaging Studies of Thin Au Film and Single Supported Au Nanoshells”

Correction to “Angle- and Momentum-Resolved Photoelectron Velocity Map Imaging Studies of Thin Au Film and Single Supported Au Nanoshells”

Correction to “Polarization-Controlled Directional Multiphoton Photoemission from Hot Spots on Single Au Nanoshells”

Correction to “Polarization-Controlled Directional Multiphoton Photoemission from Hot Spots on Single Au Nanoshells”

Two-Dimensional Silver(I)-Dithiocarboxylate Coordination Polymer Exhibiting Strong Near-Infrared Photothermal Effect.

Materials that demonstrate near-infrared (NIR) absorption and can simultaneously convert the electromagnetic irradiation into heat are promising for photothermal therapy. Traditionally, such a material is either pure inorganic, such as CuS, Ag2S, and carbon nanotube, or pure organic, such as polyaniline, polypyrrole, and conjugated polymers. Here we show that strong NIR photothermal effect can also be achieved in inorganic-organic hybrid coordination polymers (CPs) or metal-organic frameworks (MOFs). Our strategy is to construct CPs with inorganic Ag-S components that are interlinked by the organic ligands into a higher-dimensional hybrid network. Interestingly, the two resulting CPs, [Ag(Py-4-CSS)] n 1 and [Ag2(Py-4-CSS)(Py-4-CSSS)] n 2 (Py-4-CSS = pyridine-4-dithiocarboxylate; Py-4-CSSS = pyridine-4-perthiocarboxylate), show disparate structures due to the varied coordination mode of the pyridine group. For 1, the N atom coordinates to the Ag+ center and forms a two-dimensional square framework, while for 2, such a Ag-N bond is disconnected and forms only a one-dimensional structure. Interestingly, this difference leads to the distinct absorption properties in the NIR region. Under 800 nm radiation, the temperature of 1 can rise up to 24.5 °C in 3 min with photothermal conversion efficiency of 22.1%, which is about 2× that of pure inorganic Ag2S material and among the highest compared to various known inorganic materials, for example, Au nanoshells (13%), nanorods (21%), and Cu2- xSe nanocrystals (22%) irradiated with 800 nm light, while for 2, the NIR absorption is absent. This result first demonstrates that the inorganic-organic hybrid approach can be applied to construct superior NIR photothermal materials, but the control of the structure is vital. Here the coordinating nitrogen atoms in 1 are conceived to be critical in promoting the charge transfer between the dithiocarboxylate ligands. To elucidate the response to NIR irradiation of 1, we measured the heat capacity and dielectric constant of 1 and also performed density functional theory calculations. Significantly, the large dielectric constant and flat energy bands indicates 1 is much easier to be polarized and has a high electron effective mass. Thus, unlike the pure inorganic material, such as Ag2S, in which electron and hole can quantum mechanically combine to give off light, the joint-force of organic ligands in 1 effectively enhances polaronic recombination into heat.

Theoretical investigation of size, shape, and aspect ratio effect on the LSPR sensitivity of hollow-gold nanoshells.

The change in refractive index around plasmonic nanoparticles upon binding to biomolecules is routinely used in localized surface plasmon resonance (LSPR)-based biosensors and in biosensing platforms. In this study, the plasmon sensitivity of hollow gold (Au) nanoshells is studied using theoretical modeling where the influence of shape, size, shell thickness, and aspect ratio is addressed. Different shapes of hollow Au nanoshells are studied that include sphere, disk, triangular prism, rod, ellipsoid, and rectangular block. Multilayered Mie theory and discrete dipole approximation were used to determine the LSPR peak position and LSPR sensitivity as a function of size, shell thickness, shape, and aspect ratio. The change in LSPR peak wavelength per unit refractive index is defined as the sensitivity, and interesting results were obtained from the analysis. The rectangular block and rod-shaped Au nanoshells have shown maximum LSPR sensitivity when compared to other shaped Au nanoshells. In addition, increased sensitivity was observed for higher aspect ratio as well as for smaller shell thicknesses. The results are rationalized based on the inner and outer surface plasmonic coupling.

Numerical Analysis of Nonlocal Optical Response of Metallic Nanoshells

Nonlocal and quantum effects play an important role in accurately modeling the optical response of nanometer-sized metallic nanoparticles. These effects cannot be described by conventional classical theories, as they neglect essential microscopic details. Quantum hydrodynamic theory (QHT) has emerged as an excellent tool to correctly predict the nonlocal and quantum effects by taking into account the spatial dependence of the charge density. In this article, we used a QHT to investigate the impact of nonlocality and electron spill-out on the plasmonic behavior of spherical Na and Au nanoshells. We adopted a self-consistent way to compute the equilibrium charge density. The results predicted by QHT were compared with those obtained with the local response approximation (LRA) and the Thomas–Fermi hydrodynamic theory (TFHT). We found that nonlocal effects have a strong impact on both the near- and far-field optical properties of nanoshells, in particular, for the antibonding resonant mode. We also investigated the optical response of these systems for different thicknesses of the shell, both for Na and Au metals.

Gold-Nanoshell-Functionalized Polymer Nanoswimmer for Photomechanical Poration of Single-Cell Membrane.

We report an ultrasound-driven gold-nanoshell-functionalized polymer multilayer tubular nanoswimmer that can photomechanically perforate the membrane of a cancer cell by assistance of near-infrared (NIR) light. The nanoswimmers were constructed by a template-assisted layer-by-layer technique and subsequent functionalization of Au nanoshells inside the big opening. The nanoswimmers exhibit efficient and controllable movement toward target cells through the manipulation of the acoustic field. Next, the nanoswimmers with end-on attachment onto the HeLa cells achieve the poration of the cell membrane within 0.1 s under the irradiation of NIR light. The experimental and theoretical results suggest that the instantaneous photothermal effect provides enough photomechanical force to open the cell membrane. Such NIR-light-assisted nanoswimmers-enabled cell membrane poration possesses various advantages including active targeting, short time, and precision in single cells that conventional chemical and physical cell poration techniques could not achieve and, thus, provides considerable promise in a variety of biomedical applications such as gene delivery and artificial insemination.