Polyoxazoline-Based Bottlebrush and Brush-Arm Star Polymers via ROMP: Syntheses and Applications as Organic Radical Contrast Agents

Copyright © 2019 American Chemical Society. The synthesis of functional poly(2-alkyl-2-oxazoline) (PAOx) copolymers with complex nanoarchitectures using a graft-through ring-opening metathesis polymerization (ROMP) approach is described. First, well-defined norbornene-terminated poly(2-ethyl-2-oxazoline) (PEtOx) macromonomers (MM) were prepared by cationic ring-opening polymerization. ROMP of these MMs produced bottlebrush copolymers with PEtOx side chains. In addition, PEtOx-based branched MMs bearing a terminal alkyne group were prepared and conjugated to an azide-containing bis-spirocyclohexyl nitroxide via Cu-catalyzed azide-alkyne cycloaddition (CuAAC). ROMP of this branched MM, followed by in situ cross-linking, provided PEtOx-based brush-arm star polymers (BASPs) with nitroxide radicals localized at the core-shell interface. These PEtOx-based nitroxide-containing BASPs displayed relaxivity values on par with state-of-the-art polyethylene glycol (PEG)-based nitroxide materials, making them promising as organic radical contrast agents for metal-free magnetic resonance imaging (MRI)

Polymerization-Induced Self-Assembly of Block Copolymer Nano-objects via RAFT Aqueous Dispersion Polymerization

In this Perspective, we discuss the recent development of polymerization-induced self-assembly mediated by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization. This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke organic diblock copolymer nano-objects of controllable size, morphology, and surface functionality. Given its potential scalability, such environmentally-friendly formulations are expected to offer many potential applications, such as novel Pickering emulsifiers, efficient microencapsulation vehicles, and sterilizable thermo-responsive hydrogels for the cost-effective long-term storage of mammalian cells

Ambient temperature polymer modification by in situ phototriggered deprotection and thiol-ene chemistry

A novel and efficient methodology for the light-triggered release of thiols at ambient temperature is presented, which can be utilized for the in situ modification of polymeric backbones prepared via radical polymerization. Initially, a model reaction on poly(ethylene glycol) methyl ether was examined via size-exclusion chromatography coupled with electrospray ionization-mass spectrometry (SEC/ESI-MS) to establish the photodeprotection feasibility of 2-nitrobenzyl thioether moieties in the presence of variable activators or catalysts employed are Michael-type or radical thiol-ene chemistries, respectively. When 0.01 eq. of dimethylphenylphosphine is employed, disulfide coupling is reduced to its minimum and quantitative phototriggered formation of thiol-capped poly(ethylene glycol) methyl ether species is observed after a 16 hour irradiation period at 320 nm by a low-cost light source. The concept is extended to polymer backbone modification by atom transfer radical polymerization of the novel photosensitive monomer: 2-((3-((2-nitrobenzyl)thio) propanoyl)oxy)ethyl methacrylate containing the 2-nitrobenzyl thioether moiety. Well-defined homopolymers (4700 g·mol -1 ≤ M n ≤ 20000 g·mol -1, 1.29 ≤ PDI ≤ 1.40) containing one protected thiol per repeating unit were obtained and, upon a light stimulus (λ max = 320 nm), thiol entities are released along the lateral polymer chain. The photodeprotection process is mapped by exploiting the increased absorbance of photocleaved o-nitrosobenzaldehyde molecules at 345 nm and UV-Vis data suggests a quantitative backbone deprotection after a 16 hour irradiation time period. Further in situ functionalization of polymeric backbone is achieved via base-catalyzed maleimide-thiol addition at ambient temperature and its outcome is evidenced by a re-increased molecular weight in SEC, by virtue of decreased signal intensity of the 2-nitrobenzyl thioether moiety and the appearance of characteristic product protons in NMR spectroscopy (the polymer backbone functionalization is estimated as >90% by NMR analysis). © 2012 The Royal Society of Chemistry

Chemical approaches to synthetic polymer surface biofunctionalization for targeted cell adhesion using small binding motifs

In the present review the principal strategies to chemically modify the surface of synthetic polymeric materials with small molecules for targeted cell adhesion are collated and critically discussed. The focus is purposely oriented on the chemistry involved in these modifications and neither the physical characterizations nor the activity evaluations resulting from these modifications are addressed in depth, although most reviewed examples demonstrate cell adhesion. Particularly, the introduction of a chemical anchor onto the polymeric substrate, the spacing via a linker between the polymer surface and the cell-binding motif, as well as the linkage generated on this cell-binding motif are discussed. Particular cases where variable substrate geometries or spatial patterning are achieved are additionally highlighted. © 2012 The Royal Society of Chemistry

Correction: Chemical approaches to synthetic polymer surface biofunctionalization for targeted cell adhesion using small binding motifs (Soft Matter (2012) 8 (7323-7347))

Correction for ‘Chemical approaches to synthetic polymer surface biofunctionalization for targeted cell adhesion using small binding motifs’ by Guillaume Delaittre et al., Soft Matter, 2012, 8, 7323–7347

(Bio)molecular surface patterning by phototriggered oxime ligation

Making light work of ligation: A novel method utilizes light for oxime ligation chemistry. A quantitative, low-energy photodeprotection generates aldehyde, which subsequently reacts with aminooxy moieties. The spatial control allows patterning on surfaces (see scheme) with a fluoro marker and GRGSGR peptide, and can be imaged by time-of-flight secondary-ion mass spectrometry. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Diaphragmatic dysfunction in critically patients undergoing mechanical ventilation

Mechanical ventilation (MV) is an important cause of diaphragmatic weakness, associated with a syndrome known as ventilator Induced Diaphragmatic Disfunction (VIDD). The latter is determined by a heavy unload or overload of the diaphragm due to patient-ventilator asynchrony. It is important to minimize the duration of MV to optimize respiratory muscle function and to develop successful strategies that reduce the length of stay of ICU and days of MV. The primary endpoint of this project is to evaluate the ability of ultrasound in evaluating diaphragmatic contractility in relation to a possible diaphragm injury, as well as serum markers of muscle injury, during assisted MV. We will evaluate the relationship between diaphragmatic thickness and displacement with ventilator parameters (e.g. Eadi, Eadi max), titrate Neurally Adjusted Ventilator Assist (NAVA) level or PSV level assistance in order to improve ventilator trigger delay and synchrony, assessed by diaphragmatic ultrasonography

Three-dimensional cell culture on microscaffolds with spatially resolved surface chemistry

To spatially control protein-binding and cell-attachment in three dimensions (3D) we employ a two-photon-triggered cycloaddition of functional (e.g. biotinylated) dienophiles on the surface of 3D microscaffolds, which have been silanized with photoactivatable diens (photoenol). © 2014 Optical Society of America