The optimization of the enhancement of Raman scattering by plasmonic effects is largely determined by the properties of the enhancing substrates. The main parameters behind this effect are related to ...the morphology of plasmonic nanoparticles and their relative distribution within the substrate. We focus this
tutorial review
on the effects of nanoparticle morphology, for the particular case of anisotropic metal nanoparticles. Anisotropy in silver and gold nanoparticles offers the possibility to tailor their plasmonic properties and intrinsic electromagnetic "hotspots". We describe the effect of varying particle size and shape on the SERS signal, focusing on the most common anisotropic morphologies used for SERS. Especial emphasis is made on existing comparative studies that shed light on the effect of nanoparticle anisotropy on their enhancement capabilities. We aim at providing a general perspective toward understanding the general key factors and highlighting the difficulty in quantitatively determining SERS performance.
Anisotropy in plasmonic metal nanoparticles plays a major role in the enhancement of the Raman scattering of adsorbed molecules.
The design of compact nanoprobes for multimodal bioimaging is a current challenge and may have a major impact on diagnostics and therapeutics. Multicomponent gold-iron oxide nanoparticles have shown ...high potential as contrast agents in numerous imaging techniques due to the complementary features of iron oxide and gold nanomaterials. In this paper we describe novel gold-iron oxide Janus magnetic-plasmonic nanoparticles as versatile nanoprobes for multimodal imaging. The nanoparticles are characterized as contrast agents for different imaging techniques, including X-ray computed tomography (CT), T
-weighted nuclear magnetic resonance imaging (MRI), photoacoustic imaging (PA), dark-field and bright-field optical microscopy, transmission electron microscopy (TEM), and surface enhanced Raman spectroscopy (SERS). We discuss the effect of particle size and morphology on their performance as contrast agents and show the advantage of a Janus configuration. Additionally, the uptake of nanoparticles by cells can be simultaneously visualized in dark- and bright-field optical microscopy, SERS mapping, and electron microscopy. These complementary techniques allow a complete view of cell uptake in an artifact-free manner, with multiplexing capabilities, and with extra information regarding the nanoparticles' fate inside the cells. Altogether, the results obtained with these non-invasive techniques show the high versatility of these nanoparticles, the advantages of a Janus configuration, and their high potential in multipurpose biomedical applications.
4D printing is the 3D printing of objects that change chemically or physically in response to an external stimulus over time. Photothermally responsive shape memory materials are attractive for their ...ability to undergo remote activation. While photothermal methods using gold nanorods (AuNRs) are used for shape recovery, 3D patterning of these materials into objects with complex geometries using degradable materials is not addressed. Here, the fabrication of 3D printed shape memory bioplastics with photo‐activated shape recovery is reported. Protein‐based nanocomposites based on bovine serum albumin (BSA), poly (ethylene glycol) diacrylate (PEGDA), and AuNRs are developed for vat photopolymerization. These 3D printed bioplastics are mechanically deformed under high loads, and the proteins served as mechano‐active elements that unfolded in an energy‐dissipating mechanism that prevented fracture of the thermoset. The bioplastic object maintained its metastable shape‐programmed state under ambient conditions. Subsequently, up to 99% shape recovery is achieved within 1 min of irradiation with near‐infrared (NIR) light. Mechanical characterization and small angle X‐ray scattering (SAXS) analysis suggest that the proteins mechanically unfold during the shape programming step and may refold during shape recovery. These composites are promising materials for the fabrication of biodegradable shape‐morphing devices for robotics and medicine.
3D printed protein‐based nanocomposites with remote photothermal shape recovery are demonstrated using gold nanorods. These protein nanocomposites are mechanically deformed into a temporary shape that exhibits rapid shape recovery upon irradiation with NIR light.
Multicomponent nanoparticles are of particular interest due to a unique combination of properties at the nanoscale, which make them suitable for a wide variety of applications. Among them, Janus ...nanoparticles, presenting two distinct surface regions, can lead to specific interactions with interfaces, biomolecules, membranes
etc.
We report the synthesis of Janus nanoparticles comprising iron oxide nanospheres and gold nanostars, through two consecutive seed-mediated-growth steps. Electron tomography combining HAADF-STEM and EDX mapping has been performed to evaluate the spatial distribution of the two components of the nanoparticle, showing their clear separation in a Janus morphology. Additionally, SERS measurements assisted by magnetic separation were carried out to assess the application of combined plasmonic and magnetic properties for sensing.
The implementation of plasmonic nanoparticles in vivo remains hindered by important limitations such as biocompatibility, solubility in biological fluids, and physiological stability. A general and ...versatile protocol is presented, based on seeded emulsion polymerization, for the controlled encapsulation of gold and silver nanoparticles. This procedure enables the encapsulation of single nanoparticles as well as nanoparticle clusters inside a protecting polymer shell. Specifically, the efficient coating of nanoparticles of both metals is demonstrated, with final dimensions ranging between 50 and 200 nm, i.e., sizes of interest for bio‐applications. Such hybrid nanocomposites display extraordinary stability in high ionic strength and oxidizing environments, along with high cellular uptake, and low cytotoxicity. Overall, the prepared nanostructures are promising candidates for plasmonic applications under biologically relevant conditions.
Seeded emulsion polymerization is applied to the encapsulation of gold and silver nanoparticles, either as single nanoparticles or clustered, inside a protecting polymer shell. The hybrid nanocomposites are stable in high ionic strength and oxidizing environments, while displaying high cellular uptake and low cytotoxicity. These nanostructures are promising candidates for plasmonic applications under biologically relevant conditions.
Nanoplasmonics is a rapidly growing field of research that opens up multiple opportunities toward practical applications. The understanding of the extreme confinement of light at the nanoscale has ...facilitated the development of a wide range of interesting materials for many different fields. Nanoparticles of noble metals, such as gold or silver, present unique optical properties that may end up making a large impact on our daily lives. Modern biomedical techniques can successfully treat cancer via plasmon‐mediated photothermal therapy, in which metal nanoprobes act as intense heaters to kill cancer cells. Moreover, our society is also seeing an increasing interest in the development of alternative (green) energy sources, where plasmonic nanostructures are also considered to provide an advantage, e.g., improving the performance and feasibility of photovoltaic devices. In this progress report, relevant advances and applications of plasmonic nanoparticles, from energy to health, are discussed, and their potential implications in future society are highlighted.
Plasmonic nanoparticles present unique optical properties that render them extremely useful for application in many different fields. Current applications of plasmonic nanoparticles include their use as nanoheaters to effectively kill cancer cells, but they also contribute to the progress of solar energy technology. In this progress report, modern applications of plasmonic nanoparticles from which society may ultimately benefit are highlighted.
This work aims at learning how the size of gold nanocarriers influences the transport of DNA-alkylating antitumoral drugs. For this purpose, we devised conjugates of mercaptoethylmitomycin C (MEMC), ...a DNA alkylating agent, with gold nanoparticles of different sizes (2, 5, and 14 nm), and studied how size affects drug cytotoxicity, tumor penetrability, cellular uptake, and intracellular localization using two-dimensional (2D) and three-dimensional (3D) cell models. We show that only small, 2 nm, nanoparticles can transport MEMC efficiently to the cell nucleus, whereas MEMC cell uptake is much lower when delivered by these small nanoparticles than with the larger ones. 3D cellular models showed that smaller nanoparticles can transport MEMC toward deeper areas of tumor spheroids as compared to larger nanoparticles. We discuss the insights of this work toward the efficient delivery of DNA-targeting drugs.
Being a vital organ exposed to the external environment, the lung is susceptible to a plethora of pathogens and pollutants. This is reflected in high incidences of chronic respiratory diseases, which ...remain a leading cause of mortality world-wide and pose a persistent global burden. It is thus of paramount importance to improve our understanding of these pathologies and provide better therapeutic options. This necessitates the development of representative and physiologically relevant
models. Advances in bioengineering have enabled the development of sophisticated models that not only capture the three-dimensional architecture of the cellular environment but also incorporate the dynamics of local biophysical stimuli. However, such complex models also require novel approaches that provide reliable characterization. Within this review we explore how 3D bioprinting and nanoparticles can serve as multifaceted tools to develop such dynamic 4D printed
lung models and facilitate their characterization in the context of pulmonary fibrosis and breast cancer lung metastasis.
Abstract
Plexcitonic nanoparticles exhibit strong light‐matter interactions, mediated by localized surface plasmon resonances, and thereby promise potential applications in fields such as photonics, ...solar cells, and sensing, among others. Herein, these light‐matter interactions are investigated by UV‐visible and surface‐enhanced Raman scattering (SERS) spectroscopies, supported by finite‐difference time‐domain (FDTD) calculations. Our results reveal the importance of combining plasmonic nanomaterials and J‐aggregates with near‐zero‐refractive index. As plexcitonic nanostructures nanorattles are employed, based on J‐aggregates of the cyanine dye 5,5,6,6‐tetrachloro‐1,1‐diethyl‐3,3‐bis(4‐sulfobutyl)benzimidazolocarbocyanine (TDBC) and plasmonic silver‐coated gold nanorods, confined within mesoporous silica shells, which facilitate the adsorption of the J‐aggregates onto the metallic nanorod surface, while providing high colloidal stability. Electromagnetic simulations show that the electromagnetic field is strongly confined inside the J‐aggregate layer, at wavelengths near the upper plexcitonic mode, but it is damped toward the J‐aggregate/water interface at the lower plexcitonic mode. This behavior is ascribed to the sharp variation of dielectric properties of the J‐aggregate shell close to the plasmon resonance, which leads to a high opposite refractive index contrast between water and the TDBC shell, at the upper and the lower plexcitonic modes. This behavior is responsible for the high SERS efficiency of the plexcitonic nanorattles under both 633 nm and 532 nm laser illumination. SERS analysis showed a detection sensitivity down to the single‐nanoparticle level and, therefore, an exceptionally high average SERS intensity per particle. These findings may open new opportunities for ultrasensitive biosensing and bioimaging, as superbright and highly stable optical labels based on the strong coupling effect.
Colloidal nanoparticles (NPs) have become versatile building blocks in a wide variety of fields. Here, we discuss the state-of-the-art, current hot topics, and future directions based on the ...following aspects: narrow size-distribution NPs can exhibit protein-like properties; monodispersity of NPs is not always required; assembled NPs can exhibit collective behavior; NPs can be assembled one by one; there is more to be connected with NPs; NPs can be designed to be smart; surface-modified NPs can directly reach the cytosols of living cells.
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