Nanocoatings onto arteries via layer-by-layer deposition: toward the in vivo repair of damaged blood vessels

The deposition of polysaccharide-based self-assembled nanocoatings onto damaged arteries is described as a means not only to protect a damaged artery against thrombogenesis, but also to control the healing processes by incorporating biologically active components within the multilayer. As shown by confocal microscopy, the polysaccharide multilayer was retained on the artery in physiological condition and prevented platelet adhesion. Diffusion of the polysaccharides within the artery was also observed and may be used to efficiently target the vascular wall. The NO-precursor l-arginine was used a drug model and incorporated within the self-assembled layers.     

Fluorescence polarization studies of multicomponent polymer materials — anthracene labelled non-aqueous dispersions

Fluorescence polarization measurements have been carried out in hydrocarbon solvents on non-aqueous colloidal polymer dispersions labelled with anthracene [A] groups. The polymer particles are composed (dry volume) of 9% polyisobutylene and 91% poly(methyl methacrylate) [PMMA]. The A groups were introduced during particle synthesis using 9-anthrylmethyl methacrylate as a comonomer with MMA. The extent of polarization decreases with increasing A content of the PMMA phase and increasing temperature increases the steady state fluorescence polarization. These results can be explained in terms of immobile A groups which are sufficiently close that some energy transfer [A^*+AA+A^*] contributes to fluorescence depolarization.     

Conductive,Monodisperse Polyaniline Nanofibers of Controlled Length Using Well‐Defined Cylindrical Block Copolymer Micelles as Templates

Stable colloidal dispersions of polyaniline (PAni) nanofibers with controlled lengths from about 200 nm–1.1 μm and narrow length distributions (L_w/L_n<1.04; L_w=weight average micelle length, L_n=number average micelle length) were prepared through the template‐directed synthesis of PAni using monodisperse, solution‐self‐assembled, cylindrical, block copolymer micelles as nanoscale templates. These micelles were prepared through a crystallization‐driven living self‐assembly method from a poly(ferrocenyldimethylsilane)‐b‐poly(2‐vinylpyridine) block copolymer (PFS₂₅‐b‐P2VP₄₂₅). This material was initially self‐assembled in iPrOH to form cylindrical micelles with a crystalline PFS core and a P2VP corona and lengths of up to several micrometers. Sonication of this sample then yielded short cylinders with average lengths of 90 nm and a broad length distribution (L_w/L_n=1.32). Cylindrical micelles of PFS₂₅‐b‐P2VP₄₂₅ with controlled lengths and narrow length distributions (L_w/L_n<1.04) were subsequently prepared using thermal treatment at specific temperatures between 83.5 and 92.0 °C using a 1D self‐seeding process. These samples were then employed in the template‐directed synthesis of PAni nanofibers through a two‐step procedure, where the micellar template was initially stabilised by deposition of an oligoaniline coating followed by addition of a polymeric acid dopant, resulting in PAni nanofibers in the emeraldine salt (ES) state. The ES–PAni nanofibers were shown to be conductive by scanning conductance microscopy, whereas the precursor PFS₂₅‐b‐P2VP₄₂₅ micelle templates were found to be dielectric in character.     

Stimulus-responsive self-assembly: reversible, redox-controlled micellization of polyferrocenylsilane diblock copolymers

In depth studies of the use of electron transfer reactions as a means to control the self-assembly of diblock copolymers with an electroactive metalloblock are reported. Specifically, the redox-triggered self-assembly of a series of polystyrene-block-polyferrocenylsilane (PS-b-PFS) diblock copolymers in dichloromethane solution is described. In the case of the amorphous polystyrene(n)-b-poly(ferrocenylphenylmethylsilane)(m) diblock copolymers (PS(n)-b-PFMPS(m): n = 548, m = 73; n = 71, m = 165; where n and m are the number-averaged degrees of polymerization), spherical micelles with an oxidized PFS core and a PS corona were formed upon oxidation of more than 50% of the ferrocenyl units by [N(C(6)H(4)Br-4)(3)][SbX(6)] (X = Cl, F). Analogous block copolymers containing a poly(ferrocenylethylmethylsilane) (PFEMS) metalloblock, which has a lower glass transition temperature, behaved similarly. However, in contrast, on replacement of the amorphous metallopolymer blocks by semicrystalline poly(ferrocenyldimethylsilane) (PFDMS) segments, a change in the observed morphology was detected with the formation of ribbon-like micelles upon oxidation of PS(535)-b-PFDMS(103) above the same threshold value. Again the coronas consisted of fully solvated PS and the core consisted of partially to fully oxidized PFS associated with the counteranions. When oxidation was performed with [N(C(6)H(4)Br-4)(3)][SbF(6)], reduction of the cores of the spherical or ribbon-like micelles with [Co(η-C(5)Me(5))(2)] enabled full recovery of the neutral chains and no significant chain scission was detected.     

Ultrafast laser based “green” synthesis of non-toxic nanoparticles in aqueous solutions

Inorganic nanoparticles offer novel promising properties for biological sensing and imaging, as well as in therapeutics. However, these applications are often complicated by the possible toxicity of conventional nanomaterials, arising as a result of inadequate purification procedures of nanoparticles obtained via synthetic pathways using toxic or non-biocompatible substances. We review novel femtosecond laser-assisted methods, which enable the preparation of metal nanomaterials in clean, biologically friendly aqueous environment (“green” synthesis) and thus completely solve the toxicity problem. The proposed methods, including laser ablation and fragmentation, make possible the production of stable metal colloids of extremely small size (∼2 nm) with a low coefficient of variation (15–25%). Those nanoparticles exhibit unique surface chemistry and can be used for bio-imaging, cancer treatment and nanoparticle-enhanced Raman spectroscopy.     

Synthesis and Aqueous Self‐Assembly of a Polyferrocenylsilane‐block‐poly(aminoalkyl methacrylate) Diblock Copolymer

Water‐soluble cylindrical micelles with an organometallic core are formed by self‐assembly of the first polyferrocenylsilane‐block‐polyacrylate block copolymer, synthesized by anionic polymerization, in water at pH 8. A transmission electron microscopy image of the micelles is shown in the Figure.     

Characterization of pyrene end-labeled poly(ethylene glycol) by high resolution MALDI time-of-flight mass spectrometry

We report the characterization of a sample of poly(ethylene glycol) (PEG, M _n = 3841, M _w/M _n = 1.01), and its derivative end-labeled with pyrenebutyrate groups, using high resolution MALDI time-of-flight mass spectrometry. A matrix of 2-(4-hydroxyphenyl-azo)benzoic acid containing a trace of either sodium chloride or potassium chloride was employed for laser desorption. Peaks due to the sodium or potassium cationized polymers were obtained, equally spaced at 44 mass units apart. For the pyrenebutyrate diester, the analysis shows that 80 ± 2% of the chains were doubly labeled, with the ramaining chains containing only a single pyrene group. Molecular weight determinations for both sets of samples were entirely consistent with size-exclusion chromatography measurements, but were obtained with greater accuracy and less ambiguity about the influence of the end groups on the hydrodynamic radius of the polymer.     

Fluorescence studies of hydrophobically-modified poly(N-isopropylacrylamides) or how to play accordion on a liposome

The coil/globule transition of polymers in solution is a favourite topic of discussion among polymer theoreticians. Here, this phenomenon is used to play a “molecular accordion” built with a thermosensitive polymer anchored to liposomes, a tune which mimics a natural process occuring in cell membranes.