Matti M. van Schooneveld

Nanocrystal core high-density lipoproteins: a multimodality contrast agent platform

High density lipoprotein (HDL) is an important natural nanoparticle that may be modified for biomedical imaging purposes. Here we developed a novel technique to create unique multimodality HDL mimicking nanoparticles by incorporation of gold, iron oxide, or quantum dot nanocrystals for computed tomography, magnetic resonance, and fluorescence imaging, respectively. By including additional labels in the corona of the particles, they were made multifunctional. The characteristics of these nanoparticles, as well as their in vitro and in vivo behavior, revealed that they closely mimic native HDL.

Improved biocompatibility and pharmacokinetics of silica nanoparticles by means of a lipid coating: a multimodality investigation

Silica is a promising carrier material for nanoparticle-facilitated drug delivery, gene therapy, and molecular imaging. Understanding of their pharmacokinetics is important to resolve bioapplicability issues. Here we report an extensive study on bare and lipid-coated silica nanoparticles in mice. Results obtained by use of a wide variety of techniques (fluorescence imaging, inductively coupled plasma mass spectrometry, magnetic resonance imaging, confocal laser scanning microscopy, and transmission electron microscopy) showed that the lipid coating, which enables straightforward functionalization and introduction of multiple properties, increases bioapplicability and improves pharmacokinetics.

Paramagnetic Lipid-Coated Silica Nanoparticles with a Fluorescent Quantum Dot Core : A New Contrast Agent Platform for Multimodality Imaging

Silica particles as a nanoparticulate carrier material for contrast agents have received considerable attention the past few years, since the material holds great promise for biomedical applications. A key feature for successful application of this material in vivo is biocompatibility, which may be significantly improved by appropriate surface modification. In this study, we report a novel strategy to coat silica particles with a dense monolayer of paramagnetic and PEGylated lipids. The silica nanoparticles carry a quantum dot in their center and are made target-specific by the conjugation of multiple alphavbeta3-integrin-specific RGD-peptides. We demonstrate their specific uptake by endothelial cells in vitro using fluorescence microscopy, quantitative fluorescence imaging, and magnetic resonance imaging. The lipid-coated silica particles introduced here represent a new platform for nanoparticulate multimodality contrast agents.

In‐situ Scanning Transmission X‐Ray Microscopy of Catalytic Solids and Related Nanomaterials

The present status of in-situ scanning transmission X-ray microscopy (STXM) is reviewed, with an emphasis on the abilities of the STXM technique in comparison with electron microscopy. The experimental aspects and interpretation of X-ray absorption spectroscopy (XAS) are briefly introduced and the experimental boundary conditions that determine the potential applications for in-situ XAS and in-situ STXM studies are discussed. Nanoscale chemical imaging of catalysts under working conditions is outlined using cobalt and iron Fischer-Tropsch catalysts as showcases. In the discussion, we critically compare STXM-XAS and STEM-EELS (scanning transmission electron microscopy-electron energy loss spectroscopy) measurements and indicate some future directions of in-situ nanoscale imaging of catalytic solids and related nanomaterials.

A fluorescent, paramagnetic and PEGylated gold/silica nanoparticle for MRI, CT and fluorescence imaging

An important challenge in medical diagnostics is to design all-in-one contrast agents that can be detected with multiple techniques such as magnetic resonance imaging (MRI), X-ray computed tomography (CT), positron emission tomography (PET), single photon emission tomography (SPECT) or fluorescence imaging (FI). Although many dual labeled agents have been proposed, mainly for combined MRI/FI, constructs for three imaging modalities are scarce. Here gold/silica nanoparticles with a poly(ethylene glycol), paramagnetic and fluorescent lipid coating were synthesized, characterized and applied as trimodal contrast agents to allow for nanoparticle-enhanced imaging of macrophage cells in vitro via MRI, CT and FI, and mice livers in vivo via MRI and CT. This agent can be a useful tool in a multitude of applications, including cell tracking and target-specific molecular imaging, and is a step in the direction of truly multi-modal imaging.

Magnetic quantum dots for multimodal imaging

Multimodal contrast agents based on highly luminescent quantum dots (QDs) combined with magnetic nanoparticles (MNPs) or ions form an exciting class of new materials for bioimaging. With two functionalities integrated in a single nanoparticle, a sensitive contrast agent for two very powerful and highly complementary imaging techniques [fluorescence imaging and magnetic resonance imaging (MRI)] is obtained. In this review, the state of the art in this rapidly developing field is given. This is done by describing the developments for four different approaches to integrate the fluorescence and magnetic properties in a single nanoparticle. The first type of particles is created by the growth of heterostructures in which a QD is either overgrown with a layer of a magnetic material or linked to a (superpara, or ferro) MNP. The second approach involves doping of paramagnetic ions into QDs. A third option is to use silica or polymer nanoparticles as a matrix for the incorporation of both QDs and MNPs. Finally, it is possible to introduce chelating molecules with paramagnetic ions (e.g., Gd-DTPA) into the coordination shell of the QDs. All different approaches have resulted in recent breakthroughs and the demonstration of the capability of bioimaging using both functionalities. In addition to giving an overview of the most exciting recent developments, the pros and cons of the four different classes of bimodal contrast agents are discussed, ending with an outlook on the future of this emerging new field.

Imaging and quantifying the morphology of an organic-inorganic nanoparticle at the sub-nanometre level

The development of hybrid organic-inorganic nanoparticles is of interest for applications such as drug delivery, DNA and protein recognition, and medical diagnostics. However, the characterization of such nanoparticles remains a significant challenge due to the heterogeneous nature of these particles. Here, we report the direct visualization and quantification of the organic and inorganic components of a lipid-coated silica particle that contains a smaller semiconductor quantum dot. High-angle annular dark-field scanning transmission electron microscopy combined with electron energy loss spectroscopy was used to determine the thickness and chemical signature of molecular coating layers, the element atomic ratios, and the exact positions of different elements in single nanoparticles. Moreover, the lipid ratio and lipid phase segregation were also quantified.

Quantum dot and Cy5.5 labeled nanoparticles to investigate lipoprotein biointeractions via Förster Resonance Energy Transfer

The study of lipoproteins, natural nanoparticles comprised of lipids and apolipoproteins that transport fats throughout the body, is of key importance to better understand, treat, and prevent cardiovascular disease. In the current study, we have developed a lipoprotein-based nanoparticle that consists of a quantum dot (QD) core and Cy5.5 labeled lipidic coating. The methodology allows judicious tuning of the QD/Cy5.5 ratio, which enabled us to optimize Förster resonance energy transfer (FRET) between the QD core and the Cy5.5-labeled coating. This phenomenon allowed us to study lipoprotein-lipoprotein interactions, lipid exchange dynamics, and the influence of apolipoproteins on these processes. Moreover, we were able to study HDL-cell interactions and exploit FRET to visualize HDL association with live macrophage cells.

X-ray Imaging of Zeolite Particles at the Nanoscale : Influence of Steaming on the State of Aluminum and the Methanol-To-Olefin Reaction

In view of the limited oil reserves the methanol-to-olefin (MTO) process is an interesting catalytic route to provide raw materials for chemical industries. In the last decades, a vast number of studies have been devoted to increase our understanding of this important catalytic reaction leading to a consensus concerning the mechanism.[1–4] Accordingly, MTO is thought to proceed through the so-called “hydrocarbon pool” (HCP) mechanism,[5, 6] in which methanol is added to an organic scaffold present within the zeolite framework. This is followed by elimination of olefinic species in a closed catalytic cycle. Microporous silicoaluminophosphates and aluminosilicates, such as SAPO-34 and ZSM-5, are often used as MTO catalysts because of their unique acidic and structural properties. In the case of ZSM-5 the formation of ethene and propene is governed by two different catalytic routes,[7,8] allowing in principle to control the ethene/propene ratio. Unfortunately, throughout the MTO reaction undesired carbon deposits are formed in the narrow micropore system of ZSM-5, leading to severely restricted diffusion and therefore limited catalytic activity.[9] To overcome these limitations efforts have been made to improve the pore accessibility during synthesis,[10–12] and/or in post-synthetic steps,[13, 14] resulting in significant improvements in the diffusion properties of ZSM-5. In this work, two commercial ZSM-5 zeolites with dimensions of approximately 200–800 nm have been studied by scanning transmission X-ray microscopy (STXM). The first sample, denoted as ZSM-5-C, was calcined for 6 h at 5508C, whereas the second sample, further labeled as ZSM-5-S, was steamed for 3 h at 7008C. Details on the preparation and characteristics of ZSM-5-C and ZSM-5-S can be found in the Supporting Information (Figures S1–S13, Tables S1–S6). We will show how STXM, in combination with bulk characterization techniques, allows investigating the physicochemical properties of ZSM-5 zeolites in a novel way at the nanoscale.[ 15, 16] More specifically, detailed chemical maps, with a spatial resolution of 70 nm, have been obtained of aluminum, oxygen, and carbon, even under realistic reaction conditions.[17–19] In this manner, the influence of steaming on the state of aluminum, that is, the coordination and spatial distribution, as well as on the MTO performance, has been unraveled.

On the Surface Chemistry of Iron Oxides in Reactive Gas Atmospheres

Heterogeneous catalysis is based on the generation and subsequent combination of chemical species retained on the surface of a catalytic solid. Elementary reaction steps, that is, the dissociation of reactants and association to products, take place at the solid–gas or solid–liquid interface. Therefore, maximizing the accessible specific catalytic surface area, by reducing primary particle sizes, increases the (weight based) catalyst activity and results in higher material efficiency. However, surface and electronic properties of solids are often also significantly altered with decreasing particle sizes.[1,2] This results in size-dependent catalytic performance, better known as the particle size effect.[3–5] Although this effect has been well documented for many catalytic reactions, the exact underlying reasons for the different performance are often more difficult to access.