Self-assembly of Janus Au:Fe3O4 branched nanoparticles. From organized clusters to stimuli-responsive nanogel suprastructures

X-Ray Nanothermometry of Nanoparticles in Tumor-Mimicking Tissues under Photothermia

Temperature plays a critical role in regulating body mechanisms and indicating inflammatory processes. Local temperature increments above 42 °C are shown to kill cancer cells in tumorous tissue, leading to the development of nanoparticle-mediated thermo-therapeutic strategies for fighting oncological diseases. Remarkably, these therapeutic effects can occur without macroscopic temperature rise, suggesting localized nanoparticle heating, and minimizing side effects on healthy tissues. Nanothermometry has received considerable attention as a means of developing nanothermosensing approaches to monitor the temperature at the core of nanoparticle atoms inside cells. In this study, a label-free, direct, and universal nanoscale thermometry is proposed to monitor the thermal processes of nanoparticles under photoexcitation in the tumor environment. Gold-iron oxide nanohybrids are utilized as multifunctional photothermal agents internalized in a 3D tumor model of glioblastoma that mimics the in vivo scenario. The local temperature under near-infrared photo-excitation is monitored by X-ray absorption spectroscopy (XAS) at the Au L3 -edge (11 919 eV) to obtain their temperature in cells, deepening the knowledge of nanothermal tumor treatments. This nanothermometric approach demonstrates its potential in detecting high nanothermal changes in tumor-mimicking tissues. It offers a notable advantage by enabling thermal sensing of any element, effectively transforming any material into a nanothermometer within biological environments.

Magnetite-based Janus nanoparticles, their synthesis and biomedical applications

The advent of Janus nanoparticles has been a great breakthrough in the emerging field of nanomaterials. Janus nanoparticles refer to a single structure with two distinct chemical functions on either side. Owing to their asymmetric structures, they can be utilized in a variety of applications where monomorphic particles are insufficient. In the last decade, a wide variety of materials have been employed to fabricate Janus nanoparticles, and due to the great advantages of magnetite (Iron-oxide) NPs, they have been considered as one of the best candidates. With the main benefit of magnetic controlling, magnetite Janus nanoparticles fulfill great promises, especially in biomedical areas such as bioimaging, cancer therapies, theranostics, and biosensing. The intrinsic characteristics of magnetite Janus nanoparticles (MJNPs) even hold great potential in magnetite Janus forms of micro-/nanomotors. Despite the great interest and potential in magnetic Janus NPs, the need for a comprehensive review on MJNPs with a concentration on magnetite NPs has been overlooked. Herein, we present recent advancements in the magnetite-based Janus nanoparticles in the flourishing field of biomedicine. First, the synthesis and fabrication methods of Janus nanoparticles are discussed. Then we will delve into their intriguing biomedical applications, with a separate section for magnetite Janus micro-/nanomotors in biomedicine. And finally, the challenges and future outlook are provided. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > In Vitro Nanoparticle-Based Sensing.

Plasmonic Hybrid Nanostructures in Photocatalysis: Structures, Mechanisms, and Applications

(Sun)Light is an abundantly available sustainable source of energy that has been used in catalyzing chemical reactions for several decades now. In particular, studies related to the interaction of light with plasmonic nanostructures have been receiving increased attention. These structures display the unique property of localized surface plasmon resonance, which converts light of a specific wavelength range into hot charge carriers, along with strong local electromagnetic fields, and/or heat, which may all enhance the reaction efficiency in their own way. These unique properties of plasmonic nanoparticles can be conveniently tuned by varying the metal type, size, shape, and dielectric environment, thus prompting a research focus on rationally designed plasmonic hybrid nanostructures. In this review, the term "hybrid" implies nanomaterials that consist of multiple plasmonic or non-plasmonic materials, forming complex configurations in the geometry and/or at the atomic level. We discuss the synthetic techniques and evolution of such hybrid plasmonic nanostructures giving rise to a wide variety of material and geometric configurations. Bimetallic alloys, which result in a new set of opto-physical parameters, are compared with core-shell configurations. For the latter, the use of metal, semiconductor, and polymer shells is reviewed. Also, more complex structures such as Janus and antenna reactor composites are discussed. This review further summarizes the studies exploiting plasmonic hybrids to elucidate the plasmonic-photocatalytic mechanism. Finally, we review the implementation of these plasmonic hybrids in different photocatalytic application domains such as H₂ generation, CO₂ reduction, water purification, air purification, and disinfection.

Patchy metal nanoparticles with polymers: controllable growth and two-way self-assembly

We report a new design of polymer-patched gold nanoparticles (AuNPs) with controllable interparticle interactions in terms of their direction and strength. Patchy AuNPs (pAuNPs) are prepared through hydrophobicity-driven surface dewetting under deficient ligand exchange conditions. Using the exposed surface on pAuNPs as seeds, a highly controllable growth of AuNPs is carried out via seed-mediated growth while retaining the size of polymer domains. As guided by ligands, these pAuNPs can self-assemble directionally in two ways along the exposed surface (head-to-head) or the polymer-patched surface of pAuNPs (tail-to-tail). Control of the surface asymmetry/coverage on pAuNPs provides an important tool in balancing interparticle interactions (attraction vs. repulsion) that further tunes assembled nanostructures as clusters and nanochains. The self-assembly pathway plays a key role in determining the interparticle distance and therefore plasmon coupling of pAuNPs. Our results demonstrate a new paradigm in the directional self-assembly of anisotropic building blocks for hierarchical nanomaterials with interesting optical properties.

Photo-Responsive Self-Assembly of Plasmonic Magnetic Janus Nanoparticles

Stimuli-responsive self-assembly of nanoparticles is a versatile approach for the bottom-up fabrication of adaptive and functional nanomaterials. For this purpose, anisotropic building blocks are of particular importance due to the unique shapes and structures that can be obtained upon self-assembly. Here, we demonstrate the photo-responsive self-assembly of plasmonic magnetic "dumbbell" Janus nanoparticles (Au-Fe₃O₄) via the host-guest interaction of the supramolecular host cyclodextrin and the molecular photoswitch arylazopyrazole. We developed efficient ligand exchange procedures that enable the introduction of functional ligands, respectively, to the surface of the gold or magnetite core of the dumbbell. Our results indicate that distinct nanoparticle superstructures arise in aqueous solutions if nanoparticle aggregation is crosslinker-induced or self-induced and that the reversible formation and fragmentation of the superstructures can be modulated with light.

3D Printed Microfluidic Device for Magnetic Trapping and SERS Quantitative Evaluation of Environmental and Biomedical Analytes

Surface-enhanced Raman scattering (SERS) is an ideal technique for environmental and biomedical sensor devices due to not only the highly informative vibrational features but also to its ultrasensitive nature and possibilities toward quantitative assays. Moreover, in these areas, SERS is especially useful as water hinders most of the spectroscopic techniques such as those based on IR absorption. Despite its promising possibilities, most SERS substrates and technological frameworks for SERS detection are still restricted to research laboratories, mainly due to a lack of robust technologies and standardized protocols. We present herein the implementation of Janus magnetic/plasmonic Fe3O4/Au nanostars (JMNSs) as SERS colloidal substrates for the quantitative determination of several analytes. This multifunctional substrate enables the application of an external magnetic field for JMNSs retention at a specific position within a microfluidic channel, leading to additional amplification of the SERS signals. A microfluidic device was devised and 3D printed as a demonstration of cheap and fast production, with the potential for large-scale implementation. As low as 100 μL of sample was sufficient to obtain results in 30 min, and the chip could be reused for several cycles. To show the potential and versatility of the sensing system, JMNSs were exploited with the microfluidic device for the detection of several relevant analytes showing increasing analytical difficulty, including the comparative detection of p-mercaptobenzoic acid and crystal violet and the quantitative detection of the herbicide flumioxazin and the anticancer drug erlotinib in plasma, where calibration curves within diagnostic concentration intervals were obtained.