Nonionic Block Research Articles

Hidden structural features of multicompartment micelles revealed by cryogenic transmission electron tomography.

The demand for ever more complex nanostructures in materials and soft matter nanoscience also requires sophisticated characterization tools for reliable visualization and interpretation of internal morphological features. Here, we address both aspects and present synthetic concepts for the compartmentalization of nanoparticle peripheries as well as their in situ tomographic characterization. We first form negatively charged spherical multicompartment micelles from ampholytic triblock terpolymers in aqueous media, followed by interpolyelectrolyte complex (IPEC) formation of the anionic corona with bis-hydrophilic cationic/neutral diblock copolymers. At a 1:1 stoichiometric ratio of anionic and cationic charges, the so-formed IPECs are charge neutral and thus phase separate from solution (water). The high chain density of the ionic grafts provides steric stabilization through the neutral PEO corona of the grafted diblock copolymer and suppresses collapse of the IPEC; instead, the dense grafting results in defined nanodomains oriented perpendicular to the micellar core. We analyze the 3D arrangements of the complex and purely organic compartments, in situ, by means of cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET). We study the effect of block lengths of the cationic and nonionic block on IPEC morphology, and while 2D cryo-TEM projections suggest similar morphologies, cryo-ET and computational 3D reconstruction reveal otherwise hidden structural features, e.g., planar IPEC brushes emanating from the micellar core.

Phase transition of silica in the TMB–P123–H2O–TEOS quadru-component system: A feasible route to different mesostructured materials

Various siliceous structures were obtained using a nonionic block copolymer (Pluronic P123) surfactant and trimethylbenzene (TMB) as a hydrophobic additive by hydrolysis and condensation of tetraethoxysilane (TEOS) in a sol–gel process. The resultant materials were characterized by small-angle X-ray diffraction (SAXRD), nitrogen adsorption analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed the structure transformation from hexagonal structure (HEX) to multilamellar vesicles (MLVs) and then to mesocellular foams (MCFs) in the TMB–P123–H2O–TEOS quadru-component system. The morphology of the mesoporous silica was mainly controlled by the mass ratio of TMB/P123 resulted from the increasing volume of the hydrophobic chain of micelle of P123 that caused by more amount of TMB dissolved in the PPO segment of polymer. The fact that the occurrence of rod-like particles with curved ends and the coexistence of the MLVs and the HEX structure indicates that the MLVs are developed from the ends of HEX structures, rather than formed by a direct cooperative self-assembly mechanism. Further increasing of packing parameter of surfactant resulted from TMB addition transforms lamellar micelles to reversed micelles, leading to the formation of MCFs.

Highly ordered mesoporous bioactive glass with high surface areas using H3PO4 as the catalyst

Mesoporous bioactive glass (MBG) was obtained by the evaporation-induced self-assembly method which uses H3PO4 as catalyst and nonionic block copolymer (EO20PO70EO20, P123) as templates, respectively. Its average pore diameter, specific area and pore volume were 3.6nm, 476.7m2g−1 and 0.49cm3g−1. The structure and performance were characterized by small-angle X-ray diffraction (SAXRD), nitrogen adsorption–desorption isotherms and transmission electron micrographs (TEM). The results demonstrated that using H3PO4 as catalyst is useful to prepare MBG with larger surface area and highly ordered mesopore. In vitro bioactivity test suggested that this MBG exhibited an excellent formation of hydroxyl-carbonated apatite layer.

A facile synthesis strategy for structural property control of mesoporous alumina and its effect on catalysis for biodiesel production

A facile synthesis route for the production of mesoporous alumina (MA) with tuneable structural properties including BET surface area, pore volume and pore size was systematically investigated by tailoring the amount of template P123 used in the synthesis. The general synthesis strategy was based on a sol–gel process by hydrolysis of aluminium isopropoxide associated with nonionic block copolymer (P123) as the template in a water system. The results showed that the addition of P123 played a crucial role in the synthesis process, leading to very regular variations in the surface area (146.6–261.6m2/g), pore volume (0.164–2.152cm3/g) and pore size (3.5–29.9nm). MA-supported K species (MA-K) were prepared using KNO3 as the potassium precursor and adopted as the catalysts for biodiesel production. The introduction of K species to MA caused a reduction in the BET surface area and pore volume, but gave rise to a significant increase in pore size, especially when the K species was higher than 10%. K incorporation resulted in the formation of disordered, but significantly larger mesopores. In catalysis, by introducing 20% molar fraction of K species to MA, very high yield of biodiesel was achieved (92.2%) and further increased to 94.4% with 25% K. Based on the control of structural properties of MA, a series of MA-20K catalysts with the same K loading (20%) but different structural properties were prepared by varying P123 addition and were further tested in biodiesel synthesis. Higher biodiesel yields were obtained over the MAs with higher surface area, pore volume and bigger pore size, which were attributed to the reduced mass transfer limitation in catalysis.

Magnetic solid-phase extraction based on mesoporous silica-coated magnetic nanoparticles for analysis of oral antidiabetic drugs in human plasma

In the present work, magnetic nanoparticles embedded into mesoporous silica were prepared in two steps: first, magnetite was synthesized by oxidation–precipitation method, and next, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. The mesoporous SiO2-coated Fe3O4 samples were functionalized using octadecyltrimethoxysilane as silanizing agent. The pure and functionalized silica nanoparticles were physicochemically and morphologically characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The resultant magnetic silica nanoparticles were applied as sorbents for magnetic solid-phase extraction (MSPE) of oral antidiabetic drugs in human plasma. Our results revealed that the magnetite nanoparticles were completely coated by well-ordered mesoporous silica with free pores and stable pore walls, and that the structural and magnetic properties of the Fe3O4 nanoparticles were preserved in the applied synthesis route. Indeed, the sorbent material was capable of extracting the antidiabetic drugs from human plasma, being useful for the sample preparation in biological matrices.

Ordered Mesoporous Metal–Organic Frameworks Incorporated with Amorphous TiO2 As Photocatalyst for Selective Aerobic Oxidation in Sunlight Irradiation

Among the very few efforts for preparation of stable mesoporous metal–organic frameworks (MOFs), there is no report of an additive-free example via a surfactant-assisted templating method. On the other hand, photocatalytic aerobic oxidation of alcohols mediated by crystalline TiO2 has been known as a green route, which has the potential to replace current technology with transition-metal-containing heterogeneous systems. Here, a simple procedure for preparation of HKUST-1 containing ordered mesoporous domains has been developed using nonionic block copolymer in DMF as the solvent. All materials have been thoroughly characterized by FTIR, FESEM, HRTEM, XRPD, EDS, and TG analysis. Subsequently, it has been demonstrated that incorporation of amorphous TiO2 within the prepared mesoporous MOF could successfully develope a new type of photocatalyst system for selective aerobic oxidation of benzylic alcohols with moderate to high yields in sunlight irradiation.

Effect of Sol-Gel Ageing Time on Three Dimensionally Ordered Macroporous Structure of 80SiO2-15CaO-5P2O5 Bioactive Glasses

Three dimensionally ordered macroporous bioactive glasses (3DOM-BGs), namely 80SiO 2 -15CaO-5P 2 O 5 , were synthesized by sol-gel method. PMMA colloidal crystals and non-ionic block copolymers P123 were used as cotemplates. The amorphous 3DOM-BGs had skeletal walls enclosing macropores. Such structure resulted from octahedral and tetrahedral holes of the face-centered cubic ( fcc ) closest packed PMMA templates and windows interconnecting through macropores network. The thicknesses of the walls were around 50 nm – 80 nm and the windows were 90 nm – 110 nm in diameter. These wall thickness is increased by with an increase in ageing time up to 24 h and then gradually reduced with further increase in aging time. Vibration bands of Si–O–Si and P–O were evident in infrared spectra which are in agreement with EDS spectra indicating Si, P and Ca compositions. After in vitro bioactivity testing by soaking 3DOM-BGs in simulated body fluid at 37 °C, the crystallization of amorphous calcium phosphate layers compatible to the bone component of hydroxyl carbonate apatite were rapidly formed within 3 h. These results indicated that these 3DOM-BGs resembled ideal bone implant materials. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.4755

Effect of Composition on the Phase Behavior of Ion-Containing Block Copolymers Studied by a Minimal Lattice Model

We performed Monte Carlo simulations using a minimal lattice model with short-range interactions modeled using Flory–Huggins interactions parameters, χ, to investigate morphology of ion-containing A–B diblock copolymers. A fraction of the segments in the A block, p, were ionic (labeled S) while the B block segments were nonionic (p was held fixed at 0.588). The dielectric constants of the polymers is assumed to be low, and thus charge dissociation effects are negligible. The magnitude of the χ between ion and nonionic species, determined in previous experiments on poly(styrenesulfonate)-b-poly(methyl butylene), PSS–PMB, is an order of magnitude larger than that between the nonionic segments. Simulations indicate that complex morphologies such as gyroid and perforated lamellae are obtained in symmetric block copolymers wherein the volume fraction of the B block, ϕB, is about 0.5, while simple unperforated lamellae are obtained in asymmetric block copolymers wherein ϕB is about 0.25. This result is very different from the well-established phase behavior of nonionic block copolymers but consistent with experimental results of Wang et al. [Macromolecules 2010, 43, 5306]. We also make a number of additional predictions, still awaiting an experimental verification, such as the emergence of the hexagonal phase in the weak segregation limit, and a remarkable insensitivity of the product p2χN (N is the total number of segments in a copolymer chain) at the order–disorder transition to ϕB.

Effect of carbonization treatment on the morphology and microstructure of mesoporous bioactive glass/nanocrystalline hydroxyapatite nanocomposite

Mesoporous bioactive glass/nanocrystalline hydroxyapatite (MBG–nHA) nanocomposite synthesis was prepared through evaporation-induced self-assembly method followed by in situ carbonization process, with non-ionic block copolymer as mesoporous template and carbon sphere as co-template. Conducting carbonization before calcination provided an effective and simple method of controlling the structural and morphological features of MBG–nHAs. The results show that the MBG–nHA350 nanocomposite with low carbonization temperature possessed a relatively ordered hexagonal structure, high specific surface area, and large pore volume. The increment of carbonization temperature induced the presence of micropores on the surface of the nanocomposite and increased the HA nanoparticles. These findings suggest that the surface area and pore volume of the nanocomposite decrease with increasing carbonization temperature. The structural changes in the nanocomposites were related to the inclusion of HA nanoparticles in the channels through carbonization. The in vitro bioactivity evaluation in the simulated body fluid (SBF) confirms that the MBG–nHA350 sample exhibits fast apatite formation ability, thereby denoting that the proposed method enhances the potential application of MBG–nHAs in bone tissue regeneration and drug delivery.

Water-deficient templating system: a general, versatile and efficient synthetic approach for mesoporous silicas

Bridging two current templating systems: diluted surfactant solution and liquid crystal templating approaches, water-deficient templating system allows facile control over mesostructures and morphologies of mesoporous silicas in an efficient way.

A NOVEL CO-TEMPLATING METHOD FOR HIERARCHICAL MESOPOROUS ALUMINA MONOLITHS REPLICA

In this paper, hierarchical meso/macroporous aluminas were obtained by using nonionic block copolymer EO 106 PO 70 EO 106( F 127)/agarose hydrogel as cotemplates. The hierarchical structure was confirmed by SEM, TEM and small-angle X-ray diffraction. The results showed that Al 2 O 3 exhibited a hierarchical structure with interconnected replicable macropores reproduced by agarose scaffold and ordered mesopores constructed by F 127 with uniform size. The template employed here is easy to prepare, degradable and reproducible, indicating the agarose xerogel as a promising candidate for the fabrication of porous metal oxides.

Mesoporous bioactive glass and glass–ceramics: Influence of the local structure on in vitro bioactivity

Mesoporous quaternary bioactive glasses and glass–ceramic with alkali–alkaline-earth oxide were successfully synthesized by using non-ionic block copolymer P123 and evaporation induced self assembly (EISA) process followed by acid treatment assisted sol–gel method. As prepared samples has been characterized for the structural, morphological and textural properties with the various analytical techniques. Glass dissolution/ion release rate in simulated body fluid (SBF) was monitored by inductively coupled plasma (ICP) emission spectroscopy, whereas the formation of apatite phase and its crystallization at the glass and glass–ceramic surface was examined by structural, textural and microscopic probes. The influence of alkaline-earth oxide content on the glass structure followed by textural property has become more evident. The pristine glass samples exhibit a wormhole-like mesoporous structure, whereas the glass–ceramic composition is found to be in three different phases, namely crystalline hydroxyapatite, wollastonite and a residual glassy phase as observed in Cerabone® A/W. The existence of calcium orthophosphate phase is closely associated with the pore walls comprising nanometric-sized “inclusions”. The observed high surface area in conjunction with the structural features provides the possible explanation for experimentally observed enhanced bioactivity through the easy access of ions to the fluid. On the other hand, presence of multiple phases in glass–ceramic sample inhibits or delays the kinetics of apatite formation.

Comparative Studies Of Purified Poloxamer 188 Using ClotBased and Viscoelastic Measurements Of Coagulation

Background Poloxamer 188 (P188; Mast Therapeutics, Inc.) is a surface-active, non-ionic block copolymer which binds to hydrophobic surfaces on damaged cells improving membrane hydration and lowering adhesion and viscosity. It is known to improve microvascular function in various pathologic states. Currently, this agent is under investigation in a phase 3 clinical trial for treatment of sickle cell disease patients experiencing acute vaso-occlusive crisis. The effect of P188 on blood coagulation and platelet function has been evaluated in several clinical trials where no clinically significant effect has been observed. In these trials, coagulation studies were based on standard clot based methods (e.g., PT and aPTT) and did not include viscoelastic measurements such as thromboelastography (TEG). Given P188 alters viscosity, we compared the effect of this agent using various clotbased, chromogenic and viscoelastic measurements of blood coagulation. Materials and Methods Whole blood activated clotting time studies were carried out in groups of healthy individuals (n=10) at a concentration range of 1.872-15.0mg/mL. TEG analysis on native and citratedwhole blood was carried out on TEG 5000 (Haemoscope Corp, Niles, IL) at concentrations of 0-0.45 mg/mL. The effect of P188 on normal plasma clotting parameters, such as PT and aPTT, was measured at a concentration range of 0-10 mg/mL. The effect of P188 on thrombin-induced clot formation was investigated using a fibrinokinetic method. The effect of P188 on thrombin generation was measured using the fluormetric method (Technoclone, Vienna, Austria). The anti-protease effects of P188 were studied using chromogenic substrate methods using isolated biochemical systems. Results At concentrations up to 10 mg/mL, P188 did not produce any modification of Celiteactivated clotting time (Celite-ACT). At all concentrations the Celite-ACT values remained comparable to saline (138-140 sec for P188 vs. 140 sec for saline). In the TEG analysis, P188 produced a concentrationdependent hypocoagulant effect in both native and citratedblood as evidenced by increased angle and shortening of maximum amplitude (MA). In standard PT and aPTT tests, P188 did not produce any effect on the clotting profile at concentrations up to 20 mg/mL. In fibrinokinetic studies, P188 produced an increase in the fibrin clot density and rate of fibrin polymerization. Discussion These studies demonstrate that even at very high concentrations, P188 does not produce an effect on whole blood clotting as measured by the Celite-ACT assay; this result was confirmed in other standard assays. Fibrinokinetic studies revealed an increase in the rate of fibrin formation and clot density. However, at relatively low concentrations, P188 exhibited a hypocoagulant profile in TEG analysis. The marked discordance between TEG and other coagulation tests suggest that P188’s effect on viscosity and adhesive interactions result in an artifact in TEG analysis and an incorrect indication of a hypocoagulant effect. This effect may be due to the viscoelastic endpoint in the TEG assay. Further studies are needed to confirm this hypothesis. Disclosures: Fareed: Mast Therapeutics: Research Funding. Emanuele:Mast Therapeutics: Employment.

Transcriptome analysis of human multipotential mesenchymal stromal cells' response to nonionic block copolymers

Transcriptome analysis of human multipotential mesenchymal stromal cells' response to nonionic block copolymers

Surface and Adsorption Parameters of Water Soluble Polymeric Surfactants Based on Ethoxylated Schiff Base Polymers in Aqueous Medium

This work aims to measure the adsorption and micellization parameters of new water soluble nonionic amphiphilic block and graft copolymers based on hydrophilic poly (ethylene glycol) (PEG) and hydrophobic poly (propylene oxide) (PPO) at ambient temperature and normal atmospheric pressure. The chemical composition and molecular weights of the prepared copolymers were determined from 1H NMR analyses. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The surface tension, critical micelle concentration and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration, the area per molecule at interface and the effectiveness of surface tension reduction were determined from the adsorption isotherms of the prepared surfactants. Some thermodynamic data for the adsorption and micellization process were calculated and are discussed.

Effect of polyoxyethylene and polyoxypropylene nonionic block copolymers on performance and recruitment of immune cell subsets in weaned pigs

BackgroundBecause European-wide directives are restricting the non-clinical use of antibiotics as in-feed growth promotors in swine production, there is an intensive search for alternative strategies for control and prevention of losses among young pigs. With the growing knowledge of the porcine immune system and its endogenous modulation, it has been clearly established that exogenous immunomodulation using adjuvants and immune response modifiers (IRMs) represents an important prophylactic/therapeutic approach in the prevention/treatment of both stress- and microbial-induced disorders that accompaning weaning. However, it is essential to select a fully evaluated agent which may act either as a nonspecific IRM or synergistically as an adjuvant with vaccines. The synthetic macromolecules with a long history as adjuvant and IRM are nonionic block copolymers which consist of polyoxyethylene (POE) and polyoxypropylene (POP) molecules.MethodsThe aim of this work was to evaluate the effectiveness of POE-POP given as a single peroral dose on productivity parameters such as body weight gain, feed intake and feed conversion ratio, and systemic and intestinal immune parameters by assessing the proportions of CD45+ lymphoid cells, CD4+ and CD8+ T cells, and CD21+ B cells in the peripheral blood as well as the number of CD45RA+ naive lymphoid cells residing in the ileal mucosa in weaned pigs during a follow-up study 5 weeks after the treatment.ResultsPigs treated with POE-POP had better feed intake (+ 14.57%), higher average body mass at the end of the experiment (20.91 kg vs. 17.61 kg), and higher body weight gain in relation to Day 0 (191.63% vs. 144.58%) as well as in relation to nontreated pigs (+ 18.74%), with a lower feed conversion ratio (− 30.26%) in comparison to the control pigs. A much lower diarrhea severity score (5 vs. 54) was recorded in pigs treated with POE-POP (− 90.74%) than in the control pigs. A higher average diarrhea severity (ADS) was recorded in the control pigs (1.54 vs. 0.14), whereas the treatmant group had much a lower ADS ratio (− 90.91%) after 35 days of the experiment. The pigs that were treated with POE-POP had an increased proportion of CD45+, CD4+ and CD8+ cells at Day 21 (at p < 0.05, p < 0.05 or p < 0.01, respectively), Day 28 (at p < 0.01, respectively) and Day 35 (at p < 0.01, p < 0.05 or p < 0.01, respectively) as well as of CD21+ cells at Day 28 (p < 0.05) and Day 35 of the experiment (p < 0.01). Also, these pigs had more numerous CD45RA+ cells in interfollicular (p < 0.05) and follicular areas (p < 0.01) of the ileal Peyer’s patches than did control pigs.ConclusionThis property of POE-POP to induce recruitment of circulating and intestinal immune cell subsets in weaned pigs may allow the use of IRM-active block copolymers as adjuvants for vaccines, particularly those orally delivered and targeted to the gut-associated lymphoid tissues that are well known to promote rather tolerogenic than protective immune responses.

Spray-dried mesoporous silica spheres functionalized with carboxylic groups

Spherical mesoporous particles functionalized with carboxylic groups were prepared through a co-condensation route by spraying a solution containing hydrolyzed alkoxide (tetraethoxysilane) and an organosilane (4-(triethoxysilyl) butyronitrile)), in the presence of nonionic block copolymer as template. Samples have been then treated with sulfuric acid to remove the template and to hydrolyze simultaneously the –CN to –COOH groups. The mesoporous spheres show high specific surface area and narrow pore size distribution. TG and FT-IR analysis confirm the incorporation of the carboxylic moieties, whose amount results ca 1meqg−1 by titration with alkali solution. The mean size of mesoporous spheres can be ranged from few microns to submicron by varying the initial precursor concentration of spray-dried synthesis solution.

New Trends in Bioactive Glasses: The Importance of Mesostructure

A new generation templated mesoporous bioactive glasses (MBGs) with alkali oxide has been synthesized for biomedical applications with different compositions by sol-gel method. The sol-gel route involves the evaporation induced self assembly (EISA) process using non-ionic block copolymer as structure directing agent. In vitro bioactivity test on the obtained glasses after immersion in simulated body fluid has been carried out for various time durations. With the aid of four different glass systems, the role of calcium and phosphorus on in vitro bioactivity of silicate glasses has been investigated. Several analytical techniques have been used to characterize the MBG samples before and after soaking in the simulated body fluid (SBF) to establish correlation between composition, porosity and bioactivity. The quaternary glasses have been found to show rapid hydroxycarbonate apatite (HCA) formation and crystallization than ternary and binary glasses independent of Na2O/CaO content. Based on the obtained results, it has been suggested that the presence of phosphorous and calcium in the bioglass appreciably increases the rate of apatite crystallization.

Applications of polymeric adjuvants in studying autoimmune responses and vaccination against infectious diseases.

Polymers as an adjuvant are capable of enhancing the vaccine potential against various infectious diseases and also are being used to study the actual autoimmune responses using self-antigen(s) without involving any major immune deviation. Several natural polysaccharides and their derivatives originating from microbes and plants have been tested for their adjuvant potential. Similarly, numerous synthetic polymers including polyelectrolytes, polyesters, polyanhydrides, non-ionic block copolymers and external stimuli responsive polymers have demonstrated adjuvant capacity using different antigens. Adjuvant potential of these polymers mainly depends on their solubility, molecular weight, degree of branching and the conformation of polymeric backbone. These polymers have the ability not only to activate humoral but also cellular immune responses in the host. The depot effect, which involves slow release of antigen over a long duration of time, using different forms (particulate, solution and gel) of polymers, and enhances the co-stimulatory signals for optimal immune activation, is the underlying principle of their adjuvant properties. Possibly, polymers may also interact and activate various toll-like receptors and inflammasomes, thus involving several innate immune system players in the ensuing immune response. Biocompatibility, biodegradability, easy production and purification, and non-toxic properties of most of the polymers make them attractive candidates for substituting conventional adjuvants that have undesirable effects in the host.

The effect of iron incorporation on the in vitro bioactivity and drug release of mesoporous bioactive glasses

Abstract Magnetic mesoporous bioactive glasses with the composition x Fe–(80− x )SiO 2 –15CaO–5P 2 O 5 (mol%) (Fe/MBGs) were prepared by the non-ionic block copolymer EO 20 PO 70 EO 20 (P123) surfactant as template and the evaporation-induced self-assembly process using Ca, P, Si and Fe sources. The structure, morphology and magnetic properties of Fe/MBGs were characterized by X-ray diffraction, scanning electron microscopy, infrared spectra, vibrating sample magnetometer and N 2 adsorption–desorption technique. The results show that Fe/MBGs have porous network (pore diameter of 50–100 nm), mesoporous walls (mesoporous size of 4–5 nm), and that the mesostructure, magnetic properties and in vitro bioactivity of the Fe/MBGs depend on the chemical composition. Furthermore, the Fe incorporation in the MBGs enhanced the magnetic properties, demonstrated sustained drug delivery and maintained apatite-formation ability in SBF. This means that the Fe/MBGs allowed bioactivity could improve their drug delivery capacity, thus enhancing their potential applications as bioactive filler materials for bone tissue regeneration.