Supramolecular Double Helices from Small C-Symmetrical Molecules Aggregated in Water.

Supramolecular fibers in water, micrometers long and several nanometers in width, are among the most studied nanostructures for biomedical applications. These supramolecular polymers are formed through a spontaneous self-assembly process of small amphiphilic molecules by specific secondary interactions. Although many compounds do not possess a stereocenter, recent studies suggest the (co)existence of helical structures, albeit in racemic form.

Designing stable, hierarchical peptide fibers from block co-polypeptide sequences.

Natural materials, such as collagen, can assemble with multiple levels of organization in solution. Achieving a similar degree of control over morphology, stability and hierarchical organization with equilibrium synthetic materials remains elusive. For the assembly of peptidic materials the process is controlled by a complex interplay between hydrophobic interactions, electrostatics and secondary structure formation.

Disordered Filaments Mediate the Fibrillogenesis of Type I Collagen in Solution.

Collagen type I is one of the major structural proteins in mammals, providing tissues such as cornea, tendon, bone, skin, and dentin with mechanical stability, strength, and toughness. Collagen fibrils are composed of collagen molecules arranged in a quarter-stagger array that gives rise to a periodicity of 67 nm along the fibril axis, with a 30 nm overlap zone and a 37 nm gap zone. The formation of such highly organized fibrils is a self-assembly process where electrostatic and hydrophobic interactions play a critical role in determining the staggering of the molecules with 67 nm periodicity.

Liquid-Phase Electron Microscopy for Soft Matter Science and Biology.

Innovations in liquid-phase electron microscopy (LP-EM) have made it possible to perform experiments at the optimized conditions needed to examine soft matter. The main obstacle is conducting experiments in such a way that electron beam radiation can be used to obtain answers for scientific questions without changing the structure and (bio)chemical processes in the sample due to the influence of the radiation. By overcoming these experimental difficulties at least partially, LP-EM has evolved into a new microscopy method with nanometer spatial resolution and sub-second temporal resolution for analysis of soft matter in materials science and biology.

Simulation of Calcium Phosphate Prenucleation Clusters in Aqueous Solution: Association beyond Ion Pairing.

Classical molecular dynamics simulations and free energy methods have been used to obtain a better understanding of the molecular processes occurring prior to the first nucleation event for calcium phosphate biominerals. The association constants for the formation of negatively charged complexes containing calcium and phosphate ions in aqueous solution have been computed, and these results suggest that the previously proposed calcium phosphate building unit, [Ca(HPO)], should only be present in small amounts under normal experimental conditions. However, the presence of an activation barrier for the removal of an HPO ion from this complex indicates that this species could be kinetically trapped.

Crystallization by particle attachment is a colloidal assembly process.

The nucleation of crystals has long been thought to occur through the stochastic association of ions, atoms or molecules to form critical nuclei, which will later grow out to crystals. Only in the past decade has the awareness grown that crystallization can also proceed through the assembly of different types of building blocks, including amorphous precursors, primary particles, prenucleation species, dense liquid droplets or nanocrystals. However, the forces that control these alternative pathways are still poorly understood.

Osteoporotic Bone Recovery by a Highly Bone-Inductive Calcium Phosphate Polymer-Induced Liquid-Precursor.

Osteoporosis is an incurable chronic disease characterized by a lack of mineral mass in the bones. Here, the full recovery of osteoporotic bone is achieved by using a calcium phosphate polymer-induced liquid-precursor (CaP-PILP). This free-flowing CaP-PILP material displays excellent bone inductivity and is able to readily penetrate into collagen fibrils and form intrafibrillar hydroxyapatite crystals oriented along the -axis.

A Biomimetic Model for Mineralization of Type-I Collagen Fibrils.

The bone and dentin mainly consist of type-I collagen fibrils mineralized by hydroxyapatite (HAP) nanocrystals. In vitro biomimetic models based on self-assembled collagen fibrils have been widely used in studying the mineralization mechanism of type-I collagen. In this chapter, the protocol we used to build a biomimetic model for the mechanistic study of type-I collagen mineralization is described.

Liquid-liquid phase separation during amphiphilic self-assembly.

The self-assembly of amphiphilic molecules in solution is a ubiquitous process in both natural and synthetic systems. The ability to effectively control the structure and properties of these systems is essential for tuning the quality of their functionality, yet the underlying mechanisms governing the transition from molecules to assemblies have not been fully resolved. Here we describe how amphiphilic self-assembly can be preceded by liquid-liquid phase separation.

Native Chemical Ligation for Cross-Linking of Flower-Like Micelles.

In this study, native chemical ligation (NCL) was used as a selective cross-linking method to form core-cross-linked thermosensitive polymeric micelles for drug delivery applications. To this end, two complementary ABA triblock copolymers having polyethylene glycol (PEG) as midblock were synthesized by atom transfer radical polymerization (ATRP). The thermosensitive poly isopropylacrylamide (PNIPAM) outer blocks of the polymers were copolymerized with either N-(2-hydroxypropyl)methacrylamide-cysteine (HPMA-Cys), P(NIPAM- co-HPMA-Cys)-PEG-P(NIPAM- co-HPMA-Cys) (PNC) or N-(2-hydroxypropyl)methacrylamide-ethylthioglycolate succinic acid (HPMA-ETSA), P(NIPAM- co-HPMA-ETSA)-PEG-P(NIPAM- co-HPMA-ETSA) (PNE).

Microscopic structure of the polymer-induced liquid precursor for calcium carbonate.

Many biomineral crystals form complex non-equilibrium shapes, often via transient amorphous precursors. Also in vitro crystals can be grown with non-equilibrium morphologies, such as thin films or nanorods. In many cases this involves charged polymeric additives that form a polymer-induced liquid precursor (PILP).

Proteins as supramolecular hosts for C: a true solution of C in water.

Hybrid systems have great potential for a wide range of applications in chemistry, physics and materials science. Conjugation of a biosystem to a molecular material can tune the properties of the components or give rise to new properties. As a workhorse, here we take a C60@lysozyme hybrid.

Molecular nucleation mechanisms and control strategies for crystal polymorph selection.

The formation of condensed (compacted) protein phases is associated with a wide range of human disorders, such as eye cataracts, amyotrophic lateral sclerosis, sickle cell anaemia and Alzheimer's disease. However, condensed protein phases have their uses: as crystals, they are harnessed by structural biologists to elucidate protein structures, or are used as delivery vehicles for pharmaceutical applications. The physiochemical properties of crystals can vary substantially between different forms or structures ('polymorphs') of the same macromolecule, and dictate their usability in a scientific or industrial context.

A classical view on nonclassical nucleation.

Understanding and controlling nucleation is important for many crystallization applications. Calcium carbonate (CaCO) is often used as a model system to investigate nucleation mechanisms. Despite its great importance in geology, biology, and many industrial applications, CaCO nucleation is still a topic of intense discussion, with new pathways for its growth from ions in solution proposed in recent years.

CryoTEM as an Advanced Analytical Tool for Materials Chemists.

Morphology plays an essential role in chemistry through the segregation of atoms and/or molecules into different phases, delineated by interfaces. This is a general process in materials synthesis and exploited in many fields including colloid chemistry, heterogeneous catalysis, and functional molecular systems. To rationally design complex materials, we must understand and control morphology evolution.

Mesoporous Silica Nanoparticle-Coated Microneedle Arrays for Intradermal Antigen Delivery.

Purpose: To develop a new intradermal antigen delivery system by coating microneedle arrays with lipid bilayer-coated, antigen-loaded mesoporous silica nanoparticles (LB-MSN-OVA).

Methods: Synthesis of MSNs with 10-nm pores was performed and the nanoparticles were loaded with the model antigen ovalbumin (OVA), and coated with a lipid bilayer (LB-MSN-OVA). The uptake of LB-MSN-OVA by bone marrow-derived dendritic cells (BDMCs) was studied by flow cytometry.

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 in vivo, 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.

Control of magnetite nanocrystal morphology in magnetotactic bacteria by regulation of mms7 gene expression.

Living organisms can produce inorganic materials with unique structure and properties. The biomineralization process is of great interest as it forms a source of inspiration for the development of methods for production of diverse inorganic materials under mild conditions. Nonetheless, regulation of biomineralization is still a challenging task.

Bioinspired synthesis of magnetite nanoparticles.

Magnetite (Fe3O4) is a widespread magnetic iron oxide encountered in many biological and geological systems, and also in many technological applications. The magnetic properties of magnetite crystals depend strongly on the size and shape of its crystals. Hence, engineering magnetite nanoparticles with specific shapes and sizes allows tuning their properties to specific applications in a wide variety of fields, including catalysis, magnetic storage, targeted drug delivery, cancer diagnostics and magnetic resonance imaging (MRI).

CRYSTAL GROWTH. Crystallization by particle attachment in synthetic, biogenic, and geologic environments.

Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics.