Three-Dimensional Structure of P3HT Assemblies in Organic Solvents Revealed by Cryo-TEM

Poly­(3-hexylthiophene) (P3HT) assemblies in vitrified organic solvents were visualized at nanometer scale resolution by cryo-transmission electron microscopy, low dose electron diffraction, and cryo-tomography revealing a three-dimensional lamellar structure formed by the stacking of the conjugated backbones of P3HT with a distance of 1.7 nm and increased order in the bulk of the nanowire. This combination of techniques reveals local structures in dispersion and the condensed state that play a crucial role in the performance of organic electronic devices

Library of Random Copolypeptides by Solid Phase Synthesis

Random copolypeptides are promising and versatile bioinspired macromolecules of minimal complexity for studying their interactions with both living and synthetic matter. They provide the opportunity to investigate the role of, for example, total net charge and hydrophobicity through simply changing the monomer composition, without considering the effect of specific sequences or secondary structure. However, synthesizing large libraries of these polymers so far was prohibited by the time-consuming preparation methods available (ring-opening polymerization (ROP) of amino acid <i>N</i>-carboxyanhydrides and enzymatic polymerization of amino acids). Here we report the automated solid phase synthesis (SPS) of a complete library of polypeptides containing Glu, Lys, and Ala monomers with excellent control over the degree of polymerization and composition and with polydispersity indices (PDIs) between 1.01 and 1.001, which is impossible to achieve by other methods. This method provides access to a library of polymers with a precisely defined total charge that can range from approximately −15 to +15 per chain and with a disordered conformation almost completely devoid of any secondary structure. In solution the polymers are largely present as unimers, with only the most hydrophobic polypeptides showing slight signs of aggregation. Our new approach provides convenient access to libraries of this versatile class of polymers with tunable composition, which can be used in a wide variety of physicochemical studies as a tool that allows systematic variation of charge and hydrophobicity, without the interference of secondary structure or aggregation on their performance

Controlling the Distribution of Supported Nanoparticles by Aqueous Synthesis

Synthesis of supported nanoparticles with controlled size and uniform distribution is a major challenge in nanoscience, in particular for applications in catalysis. Cryo-electron tomography revealed with nanometer resolution the 3D distribution of phases present during nanoparticle synthesis via impregnation, drying, and thermal treatment with transition metal salt precursors. By conventional methods a nonuniform salt distribution led to clustered metal oxide nanoparticles (NiO, Co₃O₄). In contrast, freeze-drying restricted solution mobility during drying and a more uniform nanoparticle distribution was obtained. By this fundamental insight into catalyst preparation, controlled synthesis of supported catalysts was achieved in a way that is also applicable for other nanostructured materials

A Bioinspired Coprecipitation Method for the Controlled Synthesis of Magnetite Nanoparticles

Nature often uses precursor phases for the controlled development of crystalline materials with well-defined morphologies and unusual properties. Mimicking such a strategy in in vitro model systems would potentially lead to the water-based, room-temperature synthesis of superior materials. In the case of magnetite (Fe₃O₄), which in biology generally is formed through a ferrihydrite precursor, such approaches have remained largely unexplored. Here we report on a simple protocol that involves the slow coprecipitation of Fe^III/Fe^II salts through ammonia diffusion, during which ferrihydrite precipitates first at low pH values and is converted to magnetite at high pH values. Direct coprecipitation often leads to small crystals with superparamagnetic properties. Conversely, in this approach, the crystallization kineticsand thereby the resulting crystal sizescan be controlled through the NH₃ influx and the Fe concentration, which results in single crystals with sizes well in the ferrimagnetic domain. Moreover, this strategy provides a convenient platform for the screening of organic additives as nucleation and growth controllers, which we demonstrate for the biologically derived M6A peptide

Controlling the Distribution of Supported Nanoparticles by Aqueous Synthesis

Synthesis of supported nanoparticles with controlled size and uniform distribution is a major challenge in nanoscience, in particular for applications in catalysis. Cryo-electron tomography revealed with nanometer resolution the 3D distribution of phases present during nanoparticle synthesis via impregnation, drying, and thermal treatment with transition metal salt precursors. By conventional methods a nonuniform salt distribution led to clustered metal oxide nanoparticles (NiO, Co₃O₄). In contrast, freeze-drying restricted solution mobility during drying and a more uniform nanoparticle distribution was obtained. By this fundamental insight into catalyst preparation, controlled synthesis of supported catalysts was achieved in a way that is also applicable for other nanostructured materials

Self-Assembly of Chiral Supramolecular Ureido-Pyrimidinone-Based Poly(ethylene glycol) Polymers via Multiple Pathways

The recently developed supramolecular hydrogelator system based on poly­(ethylene glycols) end-functionalized with ureido-pyrimidinone (UPy) units has been shown to be eminently suitable as a drug delivery vehicle in soft tissues such as the heart and kidney. To understand the assembly behavior of this system in more detail, we here report on the introduction of a stereogenic center. This allowed for the investigation of the self-assembly mechanism of this system by circular dichroism, which showed the presence of helical fibers. Additionally, fluorescence spectroscopy and scattering techniques in combination with cryoTEM showed elongated rod-like structures as the major species, next to spherical micelles. Interestingly, different self-assembly pathways occurred when using two aggregate preparation methods based on different cooling rates. Both positive and negative bisignate Cotton effects were observed only by changing the method of preparation, indicating that the UPy-polymer constructs self-assemble via multiple pathways. A similar phenomenon is observed in biology, which illustrates the versatility of the system. This versatility is key to the optimization of material properties for biomedical applications

Raw Data for 'Microscopic structure of the polymer-induced liquid precursor for calcium carbonate'

<p>The data in the archive file are labelled in the following levels: </p><p><br></p><p>1st: polymer systems (ds-DNA, pAsp, pAH, pAA or no polymer)</p><p> </p><p><br></p><p>2nd: characterization methods</p><p><br></p><p>3rd: detailed experimental conditions<br></p><p><br></p><p>The Matlab script used for morphological analysis of the Tomo results could be found in the "code folder", together with the scripts for reading and writting the Tomo stacks.</p><p><br></p><p>Please feel free to contact us if you need any further information about the data.</p

Mesoporous Silica Nanoparticles with Large Pores for the Encapsulation and Release of Proteins

Mesoporous silica nanoparticles (MSNs) have been explored extensively as solid supports for proteins in biological and medical applications. Small (<200 nm) MSNs with ordered large pores (>5 nm), capable of encapsulating therapeutic small molecules suitable for delivery applications <i>in vivo</i>, are rare however. Here we present small, elongated, cuboidal, MSNs with average dimensions of 90 × 43 nm that possess disk-shaped cavities, stacked on top of each other, which run parallel to the short axis of the particle. Amine functionalization was achieved by modifying the MSN surface with 3-aminopropyl­triethoxysilane or 3-[2-(2-amino­ethyl­amino)­ethylamino]­propyl­trimethoxysilane (AP-MSNs and AEP-MSNs) and were shown to have similar dimensions to the nonfunctionalized MSNs. The dimensions of these particles, and their large surface areas as measured by nitrogen adsorption–desorption isotherms, make them ideal scaffolds for protein encapsulation and delivery. We therefore investigated the encapsulation and release behavior for seven model proteins (α-lactalbumin, ovalbumin, bovine serum albumin, catalase, hemoglobin, lysozyme, and cytochrome <i>c</i>). It was discovered that all types of MSNs used in this study allow rapid encapsulation, with a high loading capacity, for all proteins studied. Furthermore, the release profiles of the proteins were tunable. The variation in both rate and amount of protein uptake and release was found to be determined by the surface chemistry of the MSNs, together with the isoelectric point (pI), and molecular weight of the proteins, as well as by the ionic strength of the buffer. These MSNs with their large surface area and optimal dimensions provide a scaffold with a high encapsulation efficiency and controllable release profiles for a variety of proteins, enabling potential applications in fields such as drug delivery and protein therapy

Bicontinuous Nanospheres from Simple Amorphous Amphiphilic Diblock Copolymers

Bicontinuous nanospheres have been observed (although rarely) from a variety of block copolymers with architectural and compositional complexity, and often in the presence of additives. Unlocking key features involved in their formation presents possibilities for bicontinuous aggregates with varied functionality and application. An attractive prospect is the ability to form them from much simpler polymeric structures derived from facile syntheses. To that end, we herein report the formation of bicontinuous aggregates from simple amorphous amphiphilic diblock copolymers of poly­(ethylene oxide)-<i>b</i>-poly­(<i>n</i>-butyl methacrylate), analogous to our previous report of the same from a semicrystalline comb-like block copolymer. Moreover, we demonstrate that polymorphism can be achieved by altering the relative block proportions and the nonselective cosolvent. We find that the polymeric structure is not the dominating factor in the formation of bicontinuous nanospheres but that the choice of cosolvent for the hydrophilic block appears to have greater influence on determining the end morphology

Bicontinuous Nanospheres from Simple Amorphous Amphiphilic Diblock Copolymers

Bicontinuous nanospheres have been observed (although rarely) from a variety of block copolymers with architectural and compositional complexity, and often in the presence of additives. Unlocking key features involved in their formation presents possibilities for bicontinuous aggregates with varied functionality and application. An attractive prospect is the ability to form them from much simpler polymeric structures derived from facile syntheses. To that end, we herein report the formation of bicontinuous aggregates from simple amorphous amphiphilic diblock copolymers of poly­(ethylene oxide)-<i>b</i>-poly­(<i>n</i>-butyl methacrylate), analogous to our previous report of the same from a semicrystalline comb-like block copolymer. Moreover, we demonstrate that polymorphism can be achieved by altering the relative block proportions and the nonselective cosolvent. We find that the polymeric structure is not the dominating factor in the formation of bicontinuous nanospheres but that the choice of cosolvent for the hydrophilic block appears to have greater influence on determining the end morphology