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Self-assembly phenomena in block copolymer systems are attracting considerable interest from the scientific community and industry alike. Particularly interesting is the behavior of amphiphilic copolymers, which can self-organize into nanoscale-sized objects such as micelles, vesicles, or tubes in solution, and which form well-defined assemblies at interfaces such as air-liquid, air-solid, or liquid-solid. Depending on the polymer chemistry and architecture, various types of organization at interfaces can be expected, and further exploited for applications in nanotechnology, electronics, and biomedical sciences.
In this article, we discuss the formation and characterization of Langmuir monolayers from various amphiphilic block copolymers, including chargeable and thus pH-responsivematerials. Solid-supported polymer films are reviewed in the context of alteration of surface properties by ultrathin polymer layers and the possibilities for application in tissue engineering, sensors and biomaterials. Finally, we focus on how organic and polymer monolayers influence the growth of inorganic materials. This is a truly biomimetic approach since Nature uses soft interfaces to control the nucleation, growth, and morphology of biominerals such as calcium phosphate, calcium carbonate, and silica.
Silver nanoparticles (SNP) are the subject of worldwide commercialization because of their antimicrobial effects. Yet only little data on their mode of action exist. Further, only few techniques allow for visualization and quantification of unlabeled nanoparticles inside cells. To study SNP of different sizes and coatings within human macrophages, we introduce a novel laser postionization secondary neutral mass spectrometry (Laser-SNMS) approach and prove this method superior to the widely applied confocal Raman and transmission electron microscopy. With time-of-flight secondary ion mass spectrometry (TOF-SIMS) we further demonstrate characteristic fingerprints in the lipid pattern of the cellular membrane indicative of oxidative stress and membrane fluidity changes. Increases of protein carbonyl and heme oxygenase-1 levels in treated cells confirm the presence of oxidative stress biochemically. Intriguingly, affected phagocytosis reveals as highly sensitive end point of SNP-mediated adversity In macrophages. The cellular responses monitored are. hierarchically linked, but follow individual kinetics and are partially reversible.
Biomimetic hybrid materials based on a polymeric and an inorganic component such as calcium phosphate are potentially useful for bone repair. The current study reports on a new approach toward biomimetic hybrid materials using a set of recombinamers (recombinant protein materials obtained from a synthetic gene) as crystallization additive for calcium phosphate. The recombinamers contain elements from elastin, an elastic structural protein, and statherin, a salivary protein. Via genetic engineering, the basic elastin sequence was modified with the SN(A)15 domain of statherin, whose interaction with calcium phosphate is well-established. These new materials retain the biocompatibility, "smart" nature, and desired mechanical behavior of the elastin-like recombinamer (ELR) family. Mineralization in simulated body fluid (SBF) in the presence of these recombinamers reveals surprising differences. Two of the polymers inhibit calcium phosphate deposition (although they contain the statherin segment). In contrast, the third polymer, which has a triblock structure, efficiently controls the calcium phosphate formation, yielding spherical hydroxyapatite (HAP) nanoparticles with diameters from 1 to 3 nm after 1 week in SBF at 37 degrees C. However, at lower temperatures, no precipitation is observed with any of the polymers. The data thus suggest that the molecular design of ELRs containing statherin segments and the selection of an appropriate polymer structure are key parameters to obtain functional materials for the development of intelligent systems for hard tissue engineering and subsequent in vivo applications.
Biomimetic synthesis of chiral erbium-doped silver/peptide/silica core-shell nanoparticles (ESPN)
(2011)
Peptide-modified silver nanoparticles have been coated with an erbium-doped silica layer using a method inspired by silica biomineralization. Electron microscopy and small-angle X-ray scattering confirm the presence of an Ag/peptide core and silica shell. The erbium is present as small Er(2)O(3) particles in and on the silica shell. Raman, IR, UV-Vis, and circular dichroism spectroscopies show that the peptide is still present after shell formation and the nanoparticles conserve a chiral plasmon resonance. Magnetic measurements find a paramagnetic behavior. In vitro tests using a macrophage cell line model show that the resulting multicomponent nanoparticles have a low toxicity for macrophages, even on partial dissolution of the silica shell.
We have earlier shown that linear poly(ethylene imine) (LPEI) is an efficient growth modifier for calcium phosphate mineralization from aqueous solution (Shkilnyy et al., Langmuir, 2008, 24 (5), 2102). The current study addresses the growth process and the reason why LPEI is such an effective additive. To that end, the solution pH and the calcium and phosphate concentrations were monitored vs. reaction time using potentiometric, complexometric, and photometric methods. The phase transformations in the precipitates and particle morphogenesis were analyzed by X-ray diffraction and transmission electron microscopy, respectively. All measurements reveal steep decreases of the pH, calcium, and phosphate concentrations along with a rapid precipitation of brushite nanoparticles early on in the reaction. Brushite transforms into hydroxyapatite (HAP) within the first 2 h, which is much faster than what is reported, for example, for calcium phosphate precipitated with poly(acrylic acid). We propose that poly(ethylene imine) acts as a proton acceptor (weak buffer), which accelerates the transformation from brushite to HAP by taking up the protons that are released from the calcium phosphate precipitate during the phase transformation.
Commercially available 1,2-PB was transformed into a well-defined reactive intermediate by quantitative bromination. The brominated polymer was used as a polyfunctional macroinitiator for the cationic ring-opening polymerization of 2-ethyl-2-oxazoline to yield a water-soluble brush polymer. Nucleophilic substitution of bromide by 1-methyl imidazole resulted in the formation of polyelectrolyte copolymers consisting of mixed units of imidazolium, bromo, and double bond. These copolymers, which were soluble in water without forming aggregates, were used as stabilizers in the heterophase polymerization of styrene and were also studied for their ionic conducting properties.
We report on the ionothermal synthesis of porous carbon materials from a variety of carbohydrate precursors (i.e. D-glucose, D-fructose, D-xylose, and starch) using 1-butyl-3-methylimidazolium tetrachloroferrate(III), [Bmim][FeCl(4)] as a reusable solvent and catalyst. The carbon materials derived from these different carbohydrates are similar in terms of particle size and chemical composition, possessing relatively high surface areas from 44 to 155 m(2) g(-1) after ionothermal processing, which can be significantly increased to > 350 m(2) g(-1) by further thermal treatment (e. g. post-carbonization at 750 degrees C). CO(2) and N(2) sorption analysis, combined with Hg intrusion porosimetry, reveals a promising hierarchical pore structuring to these carbon materials. The ionic liquid [Bmim][FeCl(4)] has a triple role: it acts as both a soft template to generate the characterized pore structuring, solvent and as a catalyst resulting in enhanced ionothermal carbon yields. Importantly from a process point of view, the ionic liquid can be successfully recovered and reused. The current work shows that ionothermal synthesis has the potential to be an effective, low cost, and green reusable synthetic route towards sustainable porous carbon materials.
Ionic liquid Crystals constitute highly versatile materials that have drawn much interest these past few years in the fields of academic research and industrial development. In this respect, the present article is intended as an update of K. Binnemans review published in 2005, but focusing exclusively on the imidazolium cation - the most widely studied. Herein, imidazolium-containing thermotropic liquid crystalline materials will be sorted by molecular structure (mono-, bis-, poly-imidazolium compounds, with symmetrical and non-symmetrical structures) and discussed. Their physico-chemical properties will be exposed in order to adduce the relevancy and potential of the imidazolium platform in various fields of research.
Functional hybrid materials on the basis of inorganic hosts and ionic liquids (ILs) as guests hold promise for a virtually unlimited number of applications. In particular, the interaction and the combination of properties of a defined inorganic matrix and a specific IL could lead to synergistic effects in property selection and tuning. Such hybrid materials, generally termed ionogels, are thus an emerging topic in hybrid materials research. The current article addresses some of the recent developments and focuses on the question why silica is currently the dominating matrix used for (inorganic) ionogel fabrication. In comparison to silica, matrix materials such as layered simple hydroxides, layered double hydroxides, clay-type substances, magnetic or catalytically active solids, and many other compounds could be much more interesting because they themselves may carry useful functionalities, which could also be exploited for multifunctional hybrid materials synthesis. The current article combines experimental results with some arguments as to how new, advanced functional hybrid materials can be generated and which obstacles will need to be overcome to successfully achieve the synthesis of a desired target material.
The synthesis of Co-NPs and Mn-NPs by microwave-induced decomposition of the metal carbonyls Co-2(CO)(8) and Mn-2(CO)(10), respectively, yields smaller and better separated particles in the functionalized IL 1-methyl-3-(3-carboxyethyl)-imidazolium tetrafluoroborate [EmimCO(2)H][BF4] (1.6 +/- 0.3 nm and 4.3 +/- 1.0 nm, respectively) than in the non-functionalized IL 1-n-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4]. The particles are stable in the absence of capping ligands (surfactants) for more than six months although some variation in particle size could be observed by TEM.