A Fluorescent Thermometer Based on a Pyrene-Labeled Thermoresponsive Polymer

Thermoresponsive polymers that undergo a solubility transition by variation of the temperature are important materials for the development of ‘smart’ materials. In this contribution we exploit the solubility phase transition of poly(methoxy diethylene glycol methacrylate), which is accompanied by a transition from hydrophilic to hydrophobic, for the development of a fluorescent thermometer. To translate the polymer phase transition into a fluorescent response, the polymer was functionalized with pyrene resulting in a change of the emission based on the microenvironment. This approach led to a soluble polymeric fluorescent thermometer with a temperature range from 11 °C to 21 °C. The polymer phase transition that occurs during sensing is studied in detail by dynamic light scattering

Thin Polymer Brush Decouples Biomaterial's Micro-/Nano-Topology and Stem Cell Adhesion

Surface morphology and chemistry of polymers used as biomaterials, such as tissue engineering scaffolds, have a strong influence on the adhesion and behavior of human mesenchymal stem cells. Here we studied semicrystalline poly(ε-caprolactone) (PCL) substrate scaffolds, which exhibited a variation of surface morphologies and roughness originating from different spherulitic superstructures. Different substrates were obtained by varying the parameters of the thermal processing, i.e. crystallization conditions. The cells attached to these polymer substrates adopted different morphologies responding to variations in spherulite density and size. In order to decouple substrate topology effects on the cells, sub-100 nm bio-adhesive polymer brush coatings of oligo(ethylene glycol) methacrylates were grafted from PCL and functionalized with fibronectin. On surfaces featuring different surface textures, dense and sub-100 nm thick brush coatings determined the response of cells, irrespective to the underlying topology. Thus, polymer brushes decouple substrate micro-/nano-topology and the adhesion of stem cells

One step ATRP initiator immobilization on surfaces leading to gradient-grafted polymer brushes

Published: April 30, 2014A method is described that allows potentially any surface to be functionalized covalently with atom transfer radical polymerization (ATRP) initiators derived from ethyl-2-bromoisobutyrl bromide in a single step. In addition, the initiator surface density was variable and tunable such that the thickness of polymer chain grafted from the surface varied greatly on the surfaces providing examples, across the surface of a substrate, of increased chain stretching due to the entropic nature of crowded polymer chains leading toward polymer brushes. An initiator gradient of increasing surface density was deposited by plasma copolymerization of an ATRP initiator (ethyl 2-bromoisobutyrate) and a non-ATRP reactive diluent molecule (ethanol). The deposited plasma polymer retained its chemical ability to surface-initiate polymerization reactions as exemplified by N,N'-dimethyl acrylamide and poly(ethylene glycol) methyl ether methacrylate polymerizations, illustrating linear and bottle-brush-like chains, respectively. A large variation in graft thickness was observed from the low to high chain-density side suggesting that chains were forced to stretch away from the surface interface--a consequence of entropic effects resulting from increased surface crowding. The tert-butyl bromide group of ethyl 2-bromoisobutyrate is a commonly used initiator in ATRP, so a method for covalent linkage to any substrate in a single step desirably simplifies the multistep surface activation procedures currently used.Bryan R. Coad, Katie E. Styan, and Laurence Meaghe

Alkali treatment of microrough titanium surfaces affects macrophage/monocyte adhesion, platelet activation and architecture of blood clot formation

Titanium implants are most commonly used for bone augmentation and replacement due to their favorable osseointegration properties. Here, hyperhydrophilic sand-blasted and acid-etched (SBA) titanium surfaces were produced by alkali treatment and their responses to partially heparinized whole human blood were analyzed. Blood clot formation, platelet activation and activation of the complement system was analyzed revealing that exposure time between blood and the material surface is crucial as increasing exposure time results in higher amount of activated platelets, more blood clots formed and stronger complement activation. In contrast, the number of macrophages/monocytes found on alkali-treated surfaces was significantly reduced as compared to untreated SBA Ti surfaces. Interestingly, when comparing untreated to modified SBA Ti surfaces very different blood clots formed on their surfaces. On untreated Ti surfaces blood clots remain thin (below 15 mm), patchy and non-structured lacking large fibrin fiber networks whereas blood clots on differentiated surfaces assemble in an organized and layered architecture of more than 30 mm thickness. Close to the material surface most nucleated cells adhere, above large amounts of non-nucleated platelets remain entrapped within a dense fibrin fiber network providing a continuous cover of the entire surface. These findings might indicate that, combined with findings of previous in vivo studies demonstrating that alkali-treated SBA Ti surfaces perform better in terms of osseointegration, a continuous and structured layer of blood components on the blood-facing surface supports later tissue integration of an endosseous implant

Protein-Functionalized Polymer Brushes

A new strategy for the prepn. of protein-functionalized polymer brushes is reported, which is based on a combination of surface-initiated atom transfer radical polymn. (ATRP), p-nitrophenyl chloroformate activation of the surface hydroxyl groups, and subsequent O6-benzylguanine (BG) functionalization. The BG-functionalized brushes are used to chemoselectively immobilize O6-alkylguanine-DNA-alkyltransferase (AGT) fusion proteins with a defined orientation and surface d. These protein-modified polymer brushes are attractive candidates for the development of protein microarrays. [on SciFinder (R)

Polymer brushes as ionotropic matrices for the directed fabrication of microstructured calcite thin films

(Figure Presented) How to get into films: Micropatterned poly(methacrylic acid) (PMAA) brushes are used as an ionotropic matrix for the fabrication of microstructured calcite thin films. The calcite films are an exact 3D replica of the PMAA brush matrix (see Scheme; ACC = amorphous CaCO3 phase). © 2006 Wiley-VCH Verlag GmbH & Co. KGaA

Synthesis of Poly(methacrylic acid) Brushes via Surface-Initiated Atom Transfer Radical Polymerization of Sodium Methacrylate and Their Use as Substrates for the Mineralization of Calcium Carbonate 1 2 3,

This manuscript describes the synthesis of poly(methacrylic acid) (PMAA) brushes via surface-initiated atom transfer radical polymerization (SI-ATRP) of sodium methacrylate (NaMA) and their use as substrates for the mineralization of calcium carbonate. A CuBr/CuBr2/bipyridine catalyst system in aqueous solution at room temperature allowed the synthesis of brushes with thicknesses of up to 300 nm. Using substrates modified with mixtures of an ATRP-initiator modified trimethoxysilane and an "inert" pivaloyl-modified trimethoxysilane to initiate the ATRP of NaMA, a series of brushes with varying chain density could be prepared. Subsequent mineralization experiments revealed that, while low-density brushes promoted the formation of calcite crystals, high-density brushes were covered with a thin layer of amorphous CaCO3 (ACC). This is of interest because ACC can serve as a metastable precursor for different crystalline CaCO3 polymorphs and offers attractive perspectives for the bottom-up fabrication of well-defined CaCO3 crystal architectures

Synthesis of poly(methacrylic acid) brushes via surface-initiated atom transfer radical polymerization of sodium methacrylate and their use as substrates for the mineralization of calcium carbonate

This manuscript describes the synthesis of poly(methacrylic acid) (PMAA) brushes via surface-initiated atom transfer radical polymerization (SI-ATRP) of sodium methacrylate (NaMA) and their use as substrates for the mineralization of calcium carbonate. A CuBr/CuBr2/bipyridine catalyst system in aqueous solution at room temperature allowed the synthesis of brushes with thicknesses of up to 300 nm. Using substrates modified with mixtures of an ATRP-initiator modified trimethoxysilane and an "inert" pivaloyl-modified trimethoxysilane to initiate the ATRP of NaMA, a series of brushes with varying chain density could be prepared. Subsequent mineralization experiments revealed that, while low-density brushes promoted the formation of calcite crystals, high-density brushes were covered with a thin layer of amorphous CaCO3 (ACC). This is of interest because ACC can serve as a metastable precursor for different crystalline CaCO3 polymorphs and offers attractive perspectives for the bottom-up fabrication of well-defined CaCO3 crystal architectures. © 2007 American Chemical Society