title: Controlling the physical and biological properties of highly fluorescent aqueous quantum dots using block copolymers of different size and shape.
abstract: The phase transfer of fluorescent CdSe based quantum dots (QDs) while retaining their properties and offering some advantages concerning the stability and functionalization characteristics is an important and intensively investigated field of research. Here we report how to tune and control the properties of CdSe/CdS/ZnS core-shell-shell QDs in water, using poly(isoprene-block-ethylene oxide) (PI-b-PEO) as a versatile system of amphiphilic diblock copolymers for the micellular encapsulation of nanoparticles (NPs). We show the synthesis of a novel PI-b-(PEO)2 miktoarm star polymer and how this different architecture besides the variation of the polymers' molecular weight gives us the opportunity to control the size of the built constructs in water between 24 and 53 nm. Because of this size control, an upper limit of the construct's diameter for the cellular uptake could be determined by a systemic study with human alveolar epithelial cells (A549) and murine macrophage leukemia cell (RAW-264.7). Furthermore, fluorescence quenching experiments with copper(II) and iron(III) ions show a strong influence of the used polymer on the shielding against these ions. This enables us to control the permeability of the polymer shell from very porous shells, which allow an almost complete cation exchange up to very dense shells. These even offer the possibility to perform copper(I) catalyzed click reactions while keeping the fluorescence of the QDs. All these results underline the huge variability and controllability of the PI-b-PEO diblock copolymer system for the encapsulation and functionalization of nanoparticles for biological applications. As a general trend, it can be stated that those coatings, which were most stable against quenchers, also showed the best resistivity with respect to unspecific cellular uptake.
authors.affiliation: Institute of Physical Chemistry, University of Hamburg , Grindelallee 117, 20146 Hamburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Ostermann
authors.forename: Jan-Philip
authors.initials: JP
authors.lastname: Merkl
authors.forename: Sandra
authors.initials: S
authors.lastname: Flessau
authors.forename: Christopher
authors.initials: C
authors.lastname: Wolter
authors.forename: Andreas
authors.initials: A
authors.lastname: Kornowksi
authors.forename: Christian
authors.initials: C
authors.lastname: Schmidtke
authors.forename: Andrea
authors.initials: A
authors.lastname: Pietsch
authors.forename: Hauke
authors.initials: H
authors.lastname: Kloust
authors.forename: Artur
authors.initials: A
authors.lastname: Feld
authors.forename: Horst
authors.initials: H
authors.lastname: Weller
mesh_terms: D000818:Animals; D002460:Cell Line; D005453:Fluorescence; D006801:Humans; D051379:Mice; D046529:Microscopy, Electron, Transmission; D011108:Polymers / Q000737:chemistry*; D045663:Quantum Dots; D014867:Water / Q000737:chemistry*
chemical_list: D011108:Polymers; D014867:Water