Purification and Magnetic Interrogation of Hybrid Au-Fe3O4 and FePt-Fe3O4 Nanoparticles

Thermodynamics of nanocrystal–ligand binding through isothermal titration calorimetry

Manipulations of nanocrystal (NC) surfaces have propelled the applications of colloidal NCs across various fields such as bioimaging, catalysis, electronics, and sensing applications.

Recent Advances in Metal-Based Magnetic Composites as High-Efficiency Candidates for Ultrasound-Assisted Effects in Cancer Therapy

Metal-based magnetic materials have been used in different fields due to their particular physical or chemical properties. The original magnetic properties can be influenced by the composition of constituent metals. As utilized in different application fields, such as imaging monitoring, thermal treatment, and combined integration in cancer therapies, fabricated metal-based magnetic materials can be doped with target metal elements in research. Furthermore, there is one possible new trend in human activities and basic cancer treatment. As has appeared in characterizations such as magnetic resonance, catalytic performance, thermal efficiency, etc., structural information about the real morphology, size distribution, and composition play important roles in its further applications. In cancer studies, metal-based magnetic materials are considered one appropriate material because of their ability to penetrate biological tissues, interact with cellular components, and induce noxious effects. The disruptions of cytoskeletons, membranes, and the generation of reactive oxygen species (ROS) further influence the efficiency of metal-based magnetic materials in related applications. While combining with cancer cells, these magnetic materials are not only applied in imaging monitoring focus areas but also could give the exact area information in the cure process while integrating ultrasound treatment. Here, we provide an overview of metal-based magnetic materials of various types and then their real applications in the magnetic resonance imaging (MRI) field and cancer cell treatments. We will demonstrate advancements in using ultrasound fields co-worked with MRI or ROS approaches. Besides iron oxides, there is a super-family of heterogeneous magnetic materials used as magnetic agents, imaging materials, catalytic candidates in cell signaling and tissue imaging, and the expression of cancer cells and their high sensitivity to chemical, thermal, and mechanical stimuli. On the other hand, the interactions between magnetic candidates and cancer tissues may be used in drug delivery systems. The materials’ surface structure characteristics are introduced as drug loading substrates as much as possible. We emphasize that further research is required to fully characterize the mechanisms of underlying ultrasounds induced together, and their appropriate relevance for materials toxicology and biomedical applications.

Triple-Negative Breast Cancer: A Review of Conventional and Advanced Therapeutic Strategies

Triple-negative breast cancer (TNBC) cells are deficient in estrogen, progesterone and ERBB2 receptor expression, presenting a particularly challenging therapeutic target due to their highly invasive nature and relatively low response to therapeutics. There is an absence of specific treatment strategies for this tumor subgroup, and hence TNBC is managed with conventional therapeutics, often leading to systemic relapse. In terms of histology and transcription profile these cancers have similarities to BRCA-1-linked breast cancers, and it is hypothesized that BRCA1 pathway is non-functional in this type of breast cancer. In this review article, we discuss the different receptors expressed by TNBC as well as the diversity of different signaling pathways targeted by TNBC therapeutics, for example, Notch, Hedgehog, Wnt/b-Catenin as well as TGF-beta signaling pathways. Additionally, many epidermal growth factor receptor (EGFR), poly (ADP-ribose) polymerase (PARP) and mammalian target of rapamycin (mTOR) inhibitors effectively inhibit the TNBCs, but they face challenges of either resistance to drugs or relapse. The resistance of TNBC to conventional therapeutic agents has helped in the advancement of advanced TNBC therapeutic approaches including hyperthermia, photodynamic therapy, as well as nanomedicine-based targeted therapeutics of drugs, miRNA, siRNA, and aptamers, which will also be discussed. Artificial intelligence is another tool that is presented to enhance the diagnosis of TNBC.

Metal/semiconductor interfaces in nanoscale objects: synthesis, emerging properties and applications of hybrid nanostructures

Hybrid nanostructures, composed of multi-component crystals of various shapes, sizes and compositions are much sought-after functional materials. Pairing the ability to tune each material separately and controllably combine two (or more) domains with defined spatial orientation results in new properties. In this review, we discuss the various synthetic mechanisms for the formation of hybrid nanostructures of various complexities containing at least one metal/semiconductor interface, with a focus on colloidal chemistry. Different synthetic approaches, alongside the underlying kinetic and thermodynamic principles are discussed, and future advancement prospects are evaluated. Furthermore, the proved unique properties are reviewed with emphasis on the connection between the synthetic method and the resulting physical, chemical and optical properties with applications in fields such as photocatalysis.

Density gradient ultracentrifugation for colloidal nanostructures separation and investigation

In this article, we review the advancement in nanoseparation and concomitant purification of nanoparticles (NPs) by using density gradient ultracentrifugation technique (DGUC) and demonstrated by taking several typical examples. Study emphasizes the conceptual advances in classification, mechanism of DGUC and synthesis-structure-property relationships of NPs to provide the significant clue for the further synthesis optimization. Separation, concentration, and purification of NPs by DGUC can be achieved at the same time by introducing the water/oil interfaces into the separation chamber. We can develop an efficient method "lab in a tube" by introducing a reaction zone or an assembly zone in the gradient to find the surface reaction and assembly mechanism of NPs since the reaction time can be precisely controlled and the chemical environment change can be extremely fast. Finally, to achieve the best separation parameters for the colloidal systems, we gave the mathematical descriptions and computational optimized models as a new direction for making practicable and predictable DGUC separation method. Thus, it can be helpful for an efficient separation as well as for the synthesis optimization, assembly and surface reactions as a potential cornerstone for the future development in the nanotechnology and this review can be served as a plethora of advanced notes on the DGUC separation method.

Purification technologies for colloidal nanocrystals

Almost all applications of colloidal nanocrystals require some type of purification or surface modification process following nanocrystal growth. Nanocrystal purification - the separation of nanocrystals from undesired solution components - can perturb the surface chemistry and thereby the physical properties of colloidal nanocrystals due to changes in solvent, solute concentrations, and exposure of the nanocrystal surface to oxidation or hydrolysis. For example, nanocrystal quantum dots frequently exhibit decreased photoluminescence brightness after precipitation from the growth solvent and subsequent redissolution. Consequently, purification is an integral part of the synthetic chemistry of colloidal nanocrystals, and the effect of purification methods must be considered in order to accurately compare and predict the behavior of otherwise similar nanocrystal samples. In this Feature Article we examine established and emerging approaches to the purification of colloidal nanoparticles from a nanocrystal surface chemistry viewpoint. Purification is generally achieved by exploiting differences in properties between the impurities and the nanoparticles. Three distinct properties are typically manipulated: polarity (relative solubility), electrophoretic mobility, and size. We discuss precipitation, extraction, electrophoretic methods, and size-based methods including ultracentrifugation, ultrafiltration, diafiltration, and size-exclusion chromatography. The susceptibility of quantum dots to changes in surface chemistry, with changes in photoluminescence decay associated with surface chemical changes, extends even into the case of core/shell structures. Accordingly, the goal of a more complete description of quantum dot surface chemistry has been a driver of innovation in colloidal nanocrystal purification methods. We specifically examine the effect of purification on surface chemistry and photoluminescence in quantum dots as an example of the challenges associated with nanocrystal purification and how improved understanding can result from increasingly precise techniques, and associated surface-sensitive analytical methods.

Diverse Applications of Nanomedicine

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

Use of aerosol route to fabricate positively charged Au/Fe3O4 Janus nanoparticles as multifunctional nanoplatforms

Gold (Au)-decorated iron oxide (Fe₃O₄), Au/Fe₃O₄, Janus nanoparticles were fabricated via the continuous route for aerosol Au incorporation with Fe₃O₄ domains synthesized in an aqueous medium as multifunctional nanoplatforms. The fabricated nanoparticles were subsequently exposed to 185-nm UV light to generate positive charges on Au surfaces, and their activities were tested in computed tomography (CT) and magnetic resonance (MR) imaging, gene-delivery and photothermal therapy. No additional polymeric coatings of the Janus particles also had a unique ability to suppress inflammatory responses in macrophages challenged with lipopolysaccharide, which may be due to the absence of amine groups.

A uniform porous multilayer-junction thin film for enhanced gas-sensing performance

Highly-uniform In2O3/CuO bilayer and multilayer porous thin films were successfully fabricated using a self-assembled soft template and a simple sputtering deposition technique. The sensor based on the In2O3/CuO bilayer porous thin film shows obviously improved sensing performance to ethanol at a lower working temperature, compared to its single layer counterpart sensors. The response of the In2O3/CuO bilayer sensors exhibit nearly 3 and 5 times higher performance than those of the single layer In2O3 and CuO porous film sensors over the same ethanol concentration, respectively. The sensing mechanism based on the p-n hetero-junction, which contributed to the enhanced sensing performance, was also experimentally confirmed by a control experiment in which an SiO2 insulation layer was inserted between the In2O3 and CuO layers to break the p-n junction. In addition, the sensing performance can be further enhanced by increasing the number of In2O3/CuO junction layers. The facile process can be easily extended to the fabrication of other semiconductor oxide gas sensors for practical sensing applications.

Multifunctional FePt–Au heterodimers: promising nanotheranostic agents for dual-modality MR/CT imaging diagnosis and in situ cancer therapy

We report the synthesis of multifunctional FePt–Au hybrid nanoparticles via a simple hydrothermal approach and their potential application in cancer dual-modality MR/CT imaging diagnosis and simultaneous in situ therapy.

Microscopic Investigation of Chemoselectivity in Ag-Pt-Fe3O4 Heterotrimer Formation: Mechanistic Insights and Implications for Controlling High-Order Hybrid Nanoparticle Morphology

Three-component hybrid nanoparticle heterotrimers, which are important multifunctional constructs that underpin diverse applications, are commonly synthesized by growing a third domain off of a two-component heterodimer seed. However, because heterodimer seeds expose two distinct surfaces that often can both support nucleation and growth, selectively targeting one particular surface is critical for exclusively accessing a desired configuration. Understanding and controlling nucleation and growth therefore enables the rational formation of high-order hybrid nanoparticles. Here, we report an in-depth microscopic investigation that probes the chemoselective addition of Ag to Pt-Fe3O4 heterodimer seeds to form Ag-Pt-Fe3O4 heterotrimers. We find that the formation of the Ag-Pt-Fe3O4 heterotrimers initiates with indiscriminate Ag nucleation onto both the Pt and Fe3O4 surfaces of Pt-Fe3O4, followed by surface diffusion and coalescence of Ag onto the Pt surface to form the Ag-Pt-Fe3O4 product. Control experiments reveal that the size of the Ag domain of Ag-Pt-Fe3O4 correlates with the overall surface area of the Pt-Fe3O4 seeds, which is consistent with the coalescence of Ag through a surface-mediated process and can also be exploited to tune the size of the Ag domain. Additionally, we observe that small iron oxide islands on the Pt surface of the Pt-Fe3O4 seeds, deposited during the formation of Pt-Fe3O4, define the morphology of the Ag domain, which in turn influences its optical properties. These results provide unprecedented microscopic insights into the pathway by which Ag-Pt-Fe3O4 heterotrimer nanoparticles form and uncover new design guidelines for the synthesis of high-order hybrid nanoparticles with precisely targeted morphologies and properties.

Self-regulated route to ternary hybrid nanocrystals of Ag-Ag2S-CdS with near-infrared photoluminescence and enhanced photothermal conversion

Developing hybrid nanocrystals is a hot topic in materials science. Herein, a ternary hybrid nanocrystal, Ag-Ag2S-CdS, combining near infrared emission and photothermal conversion properties was demonstrated. The ternary Ag-Ag2S-CdS hybrid nanocrystals with cubic shape and uniform size were synthesized by a simple one-pot and one-step colloidal method. The growth process is self-regulated with the formation order of Ag2S, Ag, and CdS, sequentially. The formation of Ag originates from the partial reduction of Ag2S, while the formation of CdS is through an Ag2S catalytic mechanism based on its superionic feature. The obtained ternary hybrid nanocrystals show near infrared emission and photothermal conversion properties in a lab-on-a-particle system. Importantly, an enhanced effect is observed for the photothermal conversion, which is mainly due to the presence of heterointerfaces among the crystals. This work will not only advance the synthesis chemistry of multi-component hybrid nanocrystals but also provide a possible route for the design of advanced multi-model materials used in bio-related fields.

Magnetic separation of colloidal nanoparticle mixtures using a material specific peptide

A material specific peptide bound to Fe2O3 facilitates the selective sequestration of Au from a colloidal mixture of Au and CdS nanoparticles; the Au-Fe2O3 precipitate can then be magnetically separated from the colloidal CdS, and the Au nanoparticles can be recovered upon release from the Fe2O3.

Resonant tunneling modulation in quasi-2D Cu(2)O/SnO(2) p-n horizontal-multi-layer heterostructure for room temperature H(2)S sensor application

Heterostructure material that acts as resonant tunneling system is a major scientific challenge in applied physics. Herein, we report a resonant tunneling system, quasi-2D Cu(2)O/SnO(2) p-n heterostructure multi-layer film, prepared by electrochemical deposition in a quasi-2D ultra-thin liquid layer. By applying a special half-sine deposition potential across the electrodes, Cu(2)O and SnO(2) selectively and periodically deposited according to their reduction potentials. The as-prepared heterostructure film displays excellent sensitivity to H(2)S at room temperature due to the resonant tunneling modulation. Furthermore, it is found that the laser illumination could enhance the gas response, and the mechanism with laser illumination is discussed. It is the first report on gas sensing application of resonant tunneling modulation. Hence, heterostructure material act as resonant tunneling system is believed to be an ideal candidate for further improvement of room temperature gas sensing.

Full disclosure: the practical side of nanoscale total synthesis

Colloidal hybrid nanoparticles merge multiple distinct materials into single particles, producing nanostructures that often exhibit synergistic properties and multifunctionality. As the complexity of such nanostructures continues to expand and the design criteria become increasingly stringent, the synthetic pathways required to access such materials are growing in sophistication. Multistep pathways are typically needed to generate complex hybrid nanoparticles, and these synthetic protocols have important conceptual analogies to the total synthesis framework used by chemists to construct complex organic molecules. This issue of ACS Nano includes a new nanoscale total synthesis: a five-step route to Co(x)O(y)-Pt-(CdSe@CdS)-Pt-Co(x)O(y) nanorods, a material which consists of CdSe@CdS nanorods that have Pt and cobalt oxide (Co(x)O(y)) at the tips. In addition to the conceptual analogies between molecular and nanoparticle total syntheses, there are practical analogies, as well, which are important for ensuring the reproducible and high-yield production of multicomponent nanostructured products with the highest possible purities. This Perspective highlights some of the practical considerations that are important for all nanoparticle syntheses but that become magnified significantly when multiple sequential reactions are required to generate a target product. These considerations include detailed reporting of reaction setups, experimental and workup procedures, hazards, yields of all intermediates and final products, complete data analysis, and separation techniques for ensuring high purity.

Analytical methods for separating and isolating magnetic nanoparticles

Despite the large body of literature describing the synthesis of magnetic nanoparticles, few analytical tools are commonly used for their purification and analysis. Due to their unique physical and chemical properties, magnetic nanoparticles are appealing candidates for biomedical applications and analytical separations. Yet in the absence of methods for assessing and assuring their purity, the ultimate use of magnetic particles and heterostructures is likely to be limited. In this review, we summarize the separation techniques that have been initially used for this purpose. For magnetic nanoparticles, it is the use of an applied magnetic flux or field gradient that enables separations. Flow based techniques are combined with applied magnetic fields to give methods such as magnetic field flow fractionation and high gradient magnetic separation. Additional techniques have been explored for manipulating particles in microfluidic channels and in mesoporous membranes. Further development of these and new analytical tools for separation and analysis of colloidal particles is critically important to enable the practical use of these, particularly for medicinal purposes.

A total-synthesis framework for the construction of high-order colloidal hybrid nanoparticles

Colloidal hybrid nanoparticles contain multiple nanoscale domains fused together by solid-state interfaces. They represent an emerging class of multifunctional lab-on-a-particle architectures that underpin future advances in solar energy conversion, fuel-cell catalysis, medical imaging and therapy, and electronics. The complexity of these 'artificial molecules' is limited ultimately by the lack of a mechanism-driven design framework. Here, we show that known chemical reactions can be applied in a predictable and stepwise manner to build complex hybrid nanoparticle architectures that include M-Pt-Fe(3)O(4) (M = Au, Ag, Ni, Pd) heterotrimers, M(x)S-Au-Pt-Fe(3)O(4) (M = Pb, Cu) heterotetramers and higher-order oligomers based on the heterotrimeric Au-Pt-Fe(3)O(4) building block. This synthetic framework conceptually mimics the total-synthesis approach used by chemists to construct complex organic molecules. The reaction toolkit applies solid-state nanoparticle analogues of chemoselective reactions, regiospecificity, coupling reactions and molecular substituent effects to the construction of exceptionally complex hybrid nanoparticle oligomers.