Center for Applied Nanotechnology

Hamburg, Germany

Center for Applied Nanotechnology

Hamburg, Germany
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Salcher A.,University of Hamburg | Salcher A.,Center for Applied Nanotechnology | Nikolic M.S.,University of Belgrade | Casado S.,Complutense University of Madrid | And 5 more authors.
Journal of Materials Chemistry | Year: 2010

In this work, CdSe/CdS semiconductor ligand-exchanged nanoparticles have been immobilized on poly-(N-isopropylacrylamide) (pNIPAM)-based microspheres. The size and the shrinkage capacity of the spheres can be tuned by the ratio of NIPAM/styrene (pNIPAM-PS spheres) or NIPAM/BIS (N-N′-methylene-bis- acrylamide) and MA (maleic acid) (pNIPAM-BIS-MA spheres). A ligand-exchange procedure for the transfer of initially organic compatible nanoparticles into aqueous solution using amine-modified or thiol-modified poly(ethylene oxide)s (PEOs) has been carried out prior to their immobilization. We observed that the interaction of the nanoparticles with the pNIPAM-based system depends on the nature of the ligands and the chemical composition of the microspheres. Nanoparticles capped with amine- or mercapto- poly(ethylene oxide)s ligands interact with pNIPAM-PS beads while only amine-capped ones show a clear tendency to interact with pNIPAM containing acid groups which leads to a high nanoparticle coverage. Dynamic light scattering measurements, atomic force microscopy and optical spectroscopy hint that nanoparticles are placed on the surface of pNIPAM-BIS-MA beads while being partially incorporated into pNIPAM-PS network. Cell culture studies demonstrate that the fluorescent composites show non-specific binding to fibroblasts. These features may be very valuable to develop materials for drug delivery and specific targeting of cells combined with the outstanding optical properties of semiconductor nanoparticles as fluorescent labelers. © 2010 The Royal Society of Chemistry.


Kloust H.,University of Hamburg | Schmidtke C.,University of Hamburg | Feld A.,University of Hamburg | Schotten T.,Center for Applied Nanotechnology | And 9 more authors.
Langmuir | Year: 2013

Herein we demonstrate that seeded emulsion polymerization is a powerful tool to produce multiply functionalized PEO coated iron oxide nanocrystals. Advantageously, by simple addition of functional surfactants, functional monomers, or functional polymerizable linkers - solely or in combinations thereof - during the seeded emulsion polymerization process, a broad range of in situ functionalized polymer-coated iron oxide nanocrystals were obtained. This was demonstrated by purposeful modulation of the zeta potential of encapsulated iron oxide nanocrystals and conjugation of a dyestuff. Successful functionalization was unequivocally proven by TXRF. Furthermore, the spatial position of the functional groups can be controlled by choosing the appropriate spacers. In conclusion, this methodology is highly amenable for combinatorial strategies and will spur rapid expedited synthesis and purposeful optimization of a broad scope of nanocrystals. © 2013 American Chemical Society.


Feld A.,University of Hamburg | Merkl J.-P.,University of Hamburg | Kloust H.,University of Hamburg | Flessau S.,University of Hamburg | And 11 more authors.
Angewandte Chemie - International Edition | Year: 2015

Seeded emulsion polymerization is a powerful universal method to produce ultrasmall multifunctional magnetic nanohybrids. In a two-step procedure, iron oxide nanocrystals were initially encapsulated in a polystyrene (PS) shell and subsequently used as beads for a controlled assembly of elongated quantum dots/quantum rods (QDQRs). The synthesis of a continuous PS shell allows the whole construct to be fixed and the composition of the nanohybrid to be tuned. The fluorescence of the QDQRs and magnetism of iron oxide were perfectly preserved, as confirmed by single-particle investigation, fluorescence decay measurements, and relaxometry. Bio-functionalization of the hybrids was straightforward, involving copolymerization of appropriate affinity ligands as shown by immunoblot analysis. Additionally, the universality of this method was shown by the embedment of a broad scale of NPs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Feld A.,University of Hamburg | Merkl J.-P.,University of Hamburg | Kloust H.,University of Hamburg | Flessau S.,University of Hamburg | And 8 more authors.
Angewandte Chemie - International Edition | Year: 2015

Seeded emulsion polymerization is a powerful universal method to produce ultrasmall multifunctional magnetic nanohybrids. In a two-step procedure, iron oxide nanocrystals were initially encapsulated in a polystyrene (PS) shell and subsequently used as beads for a controlled assembly of elongated quantum dots/quantum rods (QDQRs). The synthesis of a continuous PS shell allows the whole construct to be fixed and the composition of the nanohybrid to be tuned. The fluorescence of the QDQRs and magnetism of iron oxide were perfectly preserved, as confirmed by single-particle investigation, fluorescence decay measurements, and relaxometry. Bio-functionalization of the hybrids was straightforward, involving copolymerization of appropriate affinity ligands as shown by immunoblot analysis. Additionally, the universality of this method was shown by the embedment of a broad scale of NPs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Schmidtke C.,University of Hamburg | Kreuziger A.-M.,University of Hamburg | Alpers D.,University of Hamburg | Jacobsen A.,University of Hamburg | And 10 more authors.
Langmuir | Year: 2013

Herein, we present a strategy for the glycoconjugation of nanoparticles (NPs), with a special focus on fluorescent quantum dots (QDs), recently described by us as "preassembly" approach. Therein, prior to the encapsulation of diverse nanoparticles by an amphiphilic poly(isoprene)-b- poly(ethylene glycol) diblock copolymer (PI-b-PEG), the terminal PEG appendage was modified by covalently attaching a carbohydrate moiety using Huisgen-type click-chemistry. Successful functionalization was proven by NMR spectroscopy. The terminally glycoconjugated polymers were subsequently used for the encapsulation of QDs in a phase transfer process, which fully preserved fluorescence properties. Binding of these nanoconstructs to the lectin Concanavalin A (Con A) was studied via surface plasmon resonance (SPR). Depending on the carbohydrate moiety, namely, d-manno-heptulose, d-glucose, d-galactose, 2-deoxy-2-{[methylamino)carbonyl]amino}-d-glucopyranose ("des(nitroso)-streptozotocin"), or d-maltose, the glycoconjugated QDs showed enhanced affinity constants due to multivalent binding effects. None of the constructs showed toxicity from 0.001 to 1 μM (particle concentration) using standard WST and LDH assays on A549 cells. © 2013 American Chemical Society.


Ostermann J.,University of Hamburg | Schmidtke C.,University of Hamburg | Wolter C.,University of Hamburg | Merkl J.-P.,University of Hamburg | And 4 more authors.
Beilstein Journal of Nanotechnology | Year: 2015

In this short review, the main challenges in the use of hydrophobic nanoparticles in biomedical application are addressed. It is shown how to overcome the different issues by the use of a polymeric encapsulation system, based on an amphiphilic polyisopreneblock- poly(ethylene glycol) diblock copolymer. On the basis of this simple molecule, the development of a versatile and powerful phase transfer strategy is summarized, focusing on the main advantages like the adjustable size, the retained properties, the excellent shielding and the diverse functionalization properties of the encapsulated nanoparticles. Finally, the extraordinary properties of these encapsulated nanoparticles in terms of toxicity and specificity in a broad in vitro test is demonstrated. © 2015 Ostermann et al.


Schmidtke C.,University of Hamburg | Kloust H.,University of Hamburg | Bastus N.G.,University of Hamburg | Bastus N.G.,Institute Catala Of Nanotecnologia Icn | And 7 more authors.
Nanoscale | Year: 2013

Herein, we present a general route towards defined nanohybrids, comprised of a fluorescent quantum dot (QD) or superparamagnetic iron oxide (Fe 2O3) nanocrystal core and a tuneable corona of plasmonic gold or silver nanoparticles (NPs), adhered by a cross-linked poly(isoprene)-b-poly(ethylene glycol) diblock copolymer (PI-b-PEG) matrix. To this end, the PEG-terminus of the amphiphilic polymer was acylated with lipoic acid (LA), which, as is known, forms quasi-covalent Au-thiol- or Ag-thiol-bonds. Surprisingly, by variation of the ratio of the different NPs, inverse core/satellite structures bearing QDs or Fe2O3 around a metallic NP core were obtained. Furthermore, gold NPs or even closed gold shells were grown by in situ reductive deposition of Au3+ ions on Fe 2O3 NP seeds. Finally, in order to demonstrate the scope of the method, ternary nanohybrids, composed of QDs, Fe2O3 and Au NPs, were accomplished. All magneto-plasmonic and fluorescent-plasmonic materials were thoroughly characterized by absorption and emission spectroscopy, TEM and TEM-EDX. Antibody conjugation to these novel nanohybrids proved their practical utility in a prototype immunoassay. © 2013 The Royal Society of Chemistry.


Schmidtke C.,University of Hamburg | Poselt E.,University of Hamburg | Ostermann J.,University of Hamburg | Pietsch A.,University of Hamburg | And 8 more authors.
Nanoscale | Year: 2013

Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging applications. However, preserving their useful properties in an aqueous biological environment remains challenging, even more as NPs therein have to be long-time stable, biocompatible and nontoxic. For in vivo applications, size control is crucial in order to route excretion pathways, e.g. renal clearance vs. hepato-biliary accumulation. Equally necessary, cellular and tissue specific targeting demands suitable linker chemistry for surface functionalization with affinity molecules, like peptides, proteins, carbohydrates and nucleotides. Herein, we report a three stage encapsulation process for NPs comprised of (1) a partial ligand exchange by a multidentate polyolefinic amine ligand, PI-N3, (2) micellar encapsulation with a precisely tuned amphiphilic diblock PI-b-PEG copolymer, in which the PI chains intercalate to the PI-N3 prepolymer and (3) radical cross-linking of the adjacent alkenyl bonds. As a result, water-soluble NPs were obtained, which virtually maintained their primal physical properties and were exceptionally stable in biological media. PEG-terminal functionalization of the diblock PI-b-PEG copolymer with numerous functional groups was mostly straightforward by chain termination of the living anionic polymerization (LAP) with the respective reagents. More complex affinity ligands, e.g. carbohydrates or biotin, were introduced in a two-step process, prior to micellar encapsulation. Advantageously, this pre-assembly approach opens up rapid access to precisely tuned multifunctional NPs, just by using mixtures of diverse functional PI-b-PEG polymers in a combinatorial manner. All constructs showed no toxicity from 0.001 to 1 μM (particle concentration) in standard WST and LDH assays on A549 cells, as well as only marginal unspecific cellular uptake, even in serum-free medium. © 2013 The Royal Society of Chemistry.


Kloust H.,University of Hamburg | Schmidtke C.,University of Hamburg | Merkl J.-P.,University of Hamburg | Feld A.,University of Hamburg | And 7 more authors.
Journal of Physical Chemistry C | Year: 2013

The polymer encapsulation of quantum dots via seeded emulsion polymerization is a powerful method for the preparation of extraordinarily stable fluorescent particles and furthermore allows simple and straightforward in situ functionalization of the polymeric shell. Both features are inevitable for the application of quantum dots as targetable fluorescent probes in advanced biomedical studies. In particular, polymer encapsulated quantum dots showed only marginal loss of quantum yields when exposed to Cu2+ ions, which under nonoptimized conditions completely quenched quantum dot fluorescence. This will allow the application of copper-catalyzed click chemistry. Furthermore, by simple addition of functional surfactants or functional monomers during the seeded emulsion polymerization process, a broad range of in situ functionalized polymer-coated quantum dots were obtained. This was demonstrated by purposeful modulation of the zeta potential encapsulated of quantum dots and conjugation of dyestuff. Successful functionalization was unequivocally proven by total reflection X-ray fluorescence. © 2013 American Chemical Society.


Schmidtke C.,University of Hamburg | Eggers R.,University of Hamburg | Zierold R.,University of Hamburg | Feld A.,University of Hamburg | And 9 more authors.
Langmuir | Year: 2014

The combination of superstructure-forming amphiphilic block copolymers and superparamagnetic iron oxide nanoparticles produces new nano/microcomposites with unique sizedependent properties. Herein, we demonstrate the controlled clustering of superparamagnetic iron oxide nanoparticles (SPIOs) ranging from discretely encapsulated SPIOs to giant clusters, containing hundreds or even more particles, using an amphiphilic polyisoprene-block-poly(ethylene glycol) diblock copolymer. Within these clusters, the SPIOs interact with each other and show new collective properties, neither obtainable with singly encapsulated nor with the bulk material. We observed cluster-size-dependent magnetic properties, influencing the blocking temperature, the magnetoviscosity of the liquid suspension, and the r2 relaxivity for magnetic iron oxide nanoparticles. The clustering methodology can be expanded also to other nanoparticle materials [CdSe/CdS/ZnS core/shell/shell quantum dots (QDs), CdSe/CdS quantum dots/quantum rods (QDQRs), gold nanoparticles, and mixtures thereof]. © 2014 American Chemical Society.

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