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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

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. Source

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

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. Source

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

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. Source

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.

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. Source

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.

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. Source

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