Membrane interaction of pegylated superparamagnetic nanoparticles

Iron oxide core-shell nanoparticles are gaining ever increasing interest for separation and imaging in biotechnology and biomedicine1,2, due to supposed low cytotoxicity and their superparamagnetic properties. Hydrophilic polymer-coated nanoparticles are believed to have low nonspecific interactions in biological systems, but much additional work in-vitro and in-vivo is needed to understand their detailed interactions with proteins, membranes and cells. We investigated monodisperse (SD\u3c5%), single-crystalline and superparamagnetic magnetite nanoparticles of different core size and densely grafted with poly(ethylene glycol) (Mw=5kDa), with particular emphasis on their interaction with biological membranes. Membrane interactions will determine nonspecific recognition and uptake by cells. These nanoparticles demonstrated no cytotoxicity and low cell uptake in in-vitro culture of HeLa and HEK cell lines. However, using Quartz Crystal Microbalance (QCM) a strong DLVO-type interaction could be demonstrated with anionic membranes that simulate eukaryote membranes. This interaction was only present in nonphysiological buffer with low ionic strength. Only low, weak and transient binding was observed to zwiterionic phosphocholine membranes. Core size seems to have an effect, with the smallest core size (3.3nm) yielding the strongest interactions while 8nm cores displayed almost no interaction. These results imply that dense polymer grafting and nanoparticle curvature are crucial parameters to control interactions between biomedical core-shell nanoparticles and their biomolecular environment, in particular cell membranes. The interaction between nanoparticle and membrane was furthermore shown to not perturb membrane structure by Differential Scanning Calorimetry (DSC). Please click Additional Files below to see the full abstract

Aligned multi-walled carbon nanotube-embodied hydrogel via low magnetic field: A strategy for engineering aligned injectable scaffolds

Injectable scaffolds are a promising strategy to restore and regenerate damaged and diseased tissues. They require minimally invasive procedure and allow the formation of an in-situ structure of any shape. However, the formation of 3D in-situ structure with aligned morphologies using a method which could be easily transferred to clinical settings remains a challenge. Herein, the rational design of an aligned injectable hydrogel-based scaffold via remote-induced alignment is reported. Carboxylated multi-walled carbon nanotubes (cMWCNT) are aligned into hydrogel via low magnetic field. The uniform dispersion and alignment of cMWCNT into the hydrogel are clearly demonstrated by small angle neutron scattering. The obtained aligned cMWCNT-embodied hydrogel is stable over 7 days at room temperature and as well at body temperature (i.e. 37 °C). As unique approach, the formation of MWCNT-hydrogel composite is investigated combining rheology with molecular dynamic and quantum mechanical calculations. The increase of MWCNT concentration into the hydrogel decreases the total energy promoting structural stabilization and increase of stiffness. The remote aligning of injectable hydrogel-based scaffold opens up horizons in the engineering of functional tissues which requires specific cell orientation.publishedVersio

Aligned multi-walled carbon nanotube-embodied hydrogel via low magnetic field : A strategy for engineering aligned injectable scaffolds

Injectable scaffolds are a promising strategy to restore and regenerate damaged and diseased tissues. They require minimally invasive procedure and allow the formation of an in-situ structure of any shape. However, the formation of 3D in-situ structure with aligned morphologies using a method which could be easily transferred to clinical settings remains a challenge. Herein, the rational design of an aligned injectable hydrogel-based scaffold via remote-induced alignment is reported. Carboxylated multi-walled carbon nanotubes (cMWCNT) are aligned into hydrogel via low magnetic field. The uniform dispersion and alignment of cMWCNT into the hydrogel are clearly demonstrated by small angle neutron scattering. The obtained aligned cMWCNT-embodied hydrogel is stable over 7 days at room temperature and as well at body temperature (i.e. 37 °C). As unique approach, the formation of MWCNT-hydrogel composite is investigated combining rheology with molecular dynamic and quantum mechanical calculations. The increase of MWCNT concentration into the hydrogel decreases the total energy promoting structural stabilization and increase of stiffness. The remote aligning of injectable hydrogel-based scaffold opens up horizons in the engineering of functional tissues which requires specific cell orientation.publishedVersionPeer reviewe

Synthesis and characterization of functionalized superparamagnetic iron oxide nanoparticles

Superparamagnetische Eisenoxid Nanopartikel (SPION) finden dank ihrer magnetischen Eigenschaften und Ungiftigkeit immer mehr Anwendung in der Biomedizin. Die Architektur als Core-Shell SPION ist besinders geeignet, da die chemische Zusammensetzung und die physikalischen Eigenschaften exakt auf die gewünschte Anwendung zugeschnitten werden können. Die Shell schützt zum einen die Cores vor Aggregation und definiert zum anderen Wechselwirkungen der SPION mit ihrer Umgebung. Das Ziel dieser Arbeit ist die Entwicklung und Anwendung solcher Core-Shell SPION. Zu Beginn wird die Synthese der SPION Cores und deren Wachstumsphasen und die Reaktionskinetik untersucht. Es wird ein Protokoll zum Austausch der nativen hydrophoben Shell gegen eine biokompatible hydrophile Shell aus Poly(ethylenglykol) (PEG) mit einem Nitrocatechol-Anker präsentiert. Weiters wird die Bedeutung der Aufreinigung des Produktes von überschüssigen und freigesetzten Liganden erörtert und als kritischer Faktor für die weitere Charakterisierung und Anwendung identifiziert. Die Verwendbarkeit der Core-Shell SPION als MRI Kontrastmittel wird evaluiert und die Aufnahme solcher SPION durch Makrophagen getestet. PEGylierte core-shell SPION und Biotin-Avidin funktionalisierte SPION werden mit herkömmlichen SPION Kontrastmitteln hinsichtlich ihrer Fähigkeit, der unspezifischen Aufnahme durch Fresszellen zu entgehen, verglichen. Core-Shell SPION sind den anderen SPION Formulierungen in MRI Messungen überlegen. Diese Eigenschaft, in Verbindung mit exzellenten stealth Eigenschaften sind der Schlüssel zur zielgerichteten MRI Bildgebung. Weiters wird ein alternativer Ligand, Sophorolipid, untersucht. Die Syntheseprinzipien für PEGylierte SPION werden erfolgreich auf die Synthese von glykosylierten SPION übertragen. Sophorolipide, immobilisiert auf SPION führen zu guter kolloidaler Stabilität und Ungiftigkeit. Dies macht glykosylierte SPION zu vielversprechenden Materialien für biomedizinische Anwendungen Superparamagnetische Eisenoxid Nanopartikel (SPION) finden dank ihrer magnetischen Eigenschaften und Ungiftigkeit immer mehr Anwendung in der Biomedizin. Die Architektur als Core-Shell SPION ist besinders geeignet, da die chemische Zusammensetzung und die physikalischen Eigenschaften exakt auf die gewünschte Anwendung zugeschnitten werden können. Die Shell schützt zum einen die Cores vor Aggregation und definiert zum anderen Wechselwirkungen der SPION mit ihrer Umgebung. Das Ziel dieser Arbeit ist die Entwicklung und Anwendung solcher Core-Shell SPION. Zu Beginn wird die Synthese der SPION Cores und deren Wachstumsphasen und die Reaktionskinetik untersucht. Es wird ein Protokoll zum Austausch der nativen hydrophoben Shell gegen eine biokompatible hydrophile Shell aus Poly(ethylenglykol) (PEG) mit einem Nitrocatechol-Anker präsentiert. Weiters wird die Bedeutung der Aufreinigung des Produktes von überschüssigen und freigesetzten Liganden erörtert und als kritischer Faktor für die weitere Charakterisierung und Anwendung identifiziert. Die Verwendbarkeit der Core-Shell SPION als MRI Kontrastmittel wird evaluiert und die Aufnahme solcher SPION durch Makrophagen getestet. PEGylierte core-shell SPION und Biotin-Avidin funktionalisierte SPION werden mit herkömmlichen SPION Kontrastmitteln hinsichtlich ihrer Fähigkeit, der unspezifischen Aufnahme durch Fresszellen zu entgehen, verglichen. Core-Shell SPION sind den anderen SPION Formulierungen in MRI Messungen überlegen. Diese Eigenschaft, in Verbindung mit exzellenten stealth Eigenschaften sind der Schlüssel zur zielgerichteten MRI Bildgebung. Weiters wird ein alternativer Ligand, Sophorolipid, untersucht. Die Syntheseprinzipien für PEGylierte SPION werden erfolgreich auf die Synthese von glykosylierten SPION übertragen. Sophorolipide, immobilisiert auf SPION führen zu guter kolloidaler Stabilität und Ungiftigkeit. Dies macht glykosylierte SPION zu vielversprechenden Materialien für biomedizinische Anwendungen.Superparamagnetic iron oxide nanoparticles (SPION) have received increasing interest for biomedical applications thanks to their unique magnetic properties paired with inherently low toxicity. Core-shell SPION are the most promising candidates as their chemical composition and physical properties can be tailored in respect to the desired application. The shell prevents the superparamagnetic cores from aggregation and defines how the nanoparticle interacts with the surrounding. The design and application of such core-shell SPION is the aim of this thesis. Starting with a detailed investigation of the SPION core synthesis, the different growth phases and reaction kinetics in SPION synthesis are revealed. A protocol to exchange the native hydrophobic ligand shell of as-synthesized SPION by a biocompatible, hydrophilic shell of poly(ethylene)glycol (PEG) bound to the SPION surface by a nitrocatechol anchor group is presented. The importance of purification from released and excess ligands is pointed out and shown to be crucial for further characterization and application. Subsequently, the applicability of PEGylated core-shell SPION as targeted MRI contrast agents is evaluated and a detailed cellular uptake study of PEGylated and biotin-avidin functionalized SPION is conducted and compared to a benchmark SPION contrast agent. The superior performance in MRI measurements of core-shell SPION over other architecture SPION is shown. These properties, along with excellent stealth properties resulting negligible cellular uptake by macrophages are the key for targeted MRI imaging. In a further study an alternative ligand, sophorolipid, was evaluated and the synthesis principles for PEGylated SPION were successfully transferred to synthesize glycosylated SPION. Immobilized on SPION, sophorolipids were shown to lead to good colloidal stability and no cytotoxicity which makes glycosylated SPION a promising and interesting material for biomedical applications Superparamagnetic iron oxide nanoparticles (SPION) have received increasing interest for biomedical applications thanks to their unique magnetic properties paired with inherently low toxicity. Core-shell SPION are the most promising candidates as their chemical composition and physical properties can be tailored in respect to the desired application. The shell prevents the superparamagnetic cores from aggregation and defines how the nanoparticle interacts with the surrounding. The design and application of such core-shell SPION is the aim of this thesis. Starting with a detailed investigation of the SPION core synthesis, the different growth phases and reaction kinetics in SPION synthesis are revealed. A protocol to exchange the native hydrophobic ligand shell of as-synthesized SPION by a biocompatible, hydrophilic shell of poly(ethylene)glycol (PEG) bound to the SPION surface by a nitrocatechol anchor group is presented. The importance of purification from released and excess ligands is pointed out and shown to be crucial for further characterization and application. Subsequently, the applicability of PEGylated core-shell SPION as targeted MRI contrast agents is evaluated and a detailed cellular uptake study of PEGylated and biotin-avidin functionalized SPION is conducted and compared to a benchmark SPION contrast agent. The superior performance in MRI measurements of core-shell SPION over other architecture SPION is shown. These properties, along with excellent stealth properties resulting negligible cellular uptake by macrophages are the key for targeted MRI imaging. In a further study an alternative ligand, sophorolipid, was evaluated and the synthesis principles for PEGylated SPION were successfully transferred to synthesize glycosylated SPION. Immobilized on SPION, sophorolipids were shown to lead to good colloidal stability and no cytotoxicity which makes glycosylated SPION a promising and interesting material for biomedical applications.submitted by Mag. Andrea LassenbergerZusammenfassung in deutscher SpracheUniversität für Bodenkultur Wien, Dissertation, 2017OeBB(VLID)193077

Complete Exchange of the Hydrophobic Dispersant Shell on Monodisperse Superparamagnetic Iron Oxide Nanoparticles

High-temperature synthesized monodisperse superparamagnetic iron oxide nanoparticles are obtained with a strongly bound ligand shell of oleic acid and its decomposition products. Most applications require a stable presentation of a defined surface chemistry; therefore, the native shell has to be completely exchanged for dispersants with irreversible affinity to the nanoparticle surface. We evaluate by attenuated total reflectance−Fourier transform infrared spectroscopy (ATR−FTIR) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) the limitations of commonly used approaches. A mechanism and multiple exchange scheme that attains the goal of complete and irreversible ligand replacement on monodisperse nanoparticles of various sizes is presented. The obtained hydrophobic nanoparticles are ideally suited for magnetically controlled drug delivery and membrane applications and for the investigation of fundamental interfacial properties of ultrasmall core–shell architectures

Biocompatible Glyconanoparticles by Grafting of Sophorolipid Monolayers on Monodisperse Iron Oxide Nanoparticles

International audienceThis work presents synthesis and characterization of sophorolipid-coated monodisperse iron oxide nanoparticles. Sophorolipids are biological glycosylated amphiphiles produced by the yeast S. bombicola. In their open acidic form, sophorolipids have been used as surface stabilizing agent for metal and metal oxide nanoparticles but with poor control over size and structural properties. In this work, the COOH function of sophorolipids (SL) was modified with nitrodopamine (NDA), a catechol known for its high affinity to iron ions. The resulting new form of sophorolipid-nitrodopamide (SL-NDA) was used as surface ligand for monodisperse iron oxide nanoparticles. We show, by a combination of thermogravimetric analysis and small angle X-ray and neutron scattering, that iron oxide nanoparticles (IONP) are stabilized by a single, high-density SL-NDA layer, which results in excellent colloidal stability under biologically relevant conditions such as high protein and salt concentration. The IONP grafted with SL-NDA showed negligible uptake and no cytotoxicity tested on two representative cell lines. Thus, they reveal the potential of sophorolipids as stable and non-toxic surface coatings for IONP-based biomedical and biotechnological applications

Individually Stabilized, Superparamagnetic Nanoparticles with Controlled Shell and Size Leading to Exceptional Stealth Properties and High Relaxivities

Superparamagnetic iron oxide nanoparticles (SPION) have received immense interest for biomedical applications, with the first clinical application as negative contrast agent in magnetic resonance imaging (MRI). However, the first generation MRI contrast agents with dextran-enwrapped, polydisperse iron oxide nanoparticle clusters are limited to imaging of the liver and spleen; this is related to their poor colloidal stability in biological media and inability to evade clearance by the reticulo­endothelial system. We investigate the qualitatively different performance of a new generation of individually PEG-grafted core–shell SPION in terms of relaxivity and cell uptake and compare them to benchmark iron oxide contrast agents. These PEG-grafted SPION uniquely enable relaxivity measurements in aqueous suspension without aggregation even at 9.4 T magnetic fields due to their extraordinary colloidal stability. This allows for determination of the size-dependent scaling of relaxivity, which is shown to follow a <i>d</i>² dependence for identical core–shell structures. The here introduced core–shell SPION with ∼15 nm core diameter yield a higher <i>R</i>₂ relaxivity than previous clinically used contrast agents as well as previous generations of individually stabilized SPION. The colloidal stability extends to control over evasion of macrophage clearance and stimulated uptake by SPION functionalized with protein ligands, which is a key requirement for targeted MRI