One-Step Facile Surface Engineering of Hydrophobic Nanocrystals with Designer Molecular Recognition

 
High quality nanocrystals have demonstrated substantial potential for biomedical applications. However, being generally hydrophobic, their use has been greatly limited by complicated and inefficient surface engineering that often fails to yield biocompatible nanocrystals with minimal aggregation in biological fluids and active targeting toward specific biomolecules. Using chimeric DNA molecules, we developed a one-step facile surface engineering method for hydrophobic nanocrystals. The procedure is simple and versatile, generating individual nanocrystals with multiple ligands. In addition, the resulting nanocrystals can actively and specifically target various molecular addresses, varying from nucleic acids to cancer cells. Together, the strategy developed here holds great promise in generating critical technologies needed for biomedical applications of nanocrystals.

The predominant role of collagen in the nucleation, growth, structure and orientation of bone apatite

Yan Wang, Thierry Azaïs, Marc Robin, Anne Vallée, Chelsea Catania, Patrick Legriel, Gérard Pehau-Arnaudet, Florence Babonneau, Marie-Madeleine Giraud-Guille & Nadine Nassif 

The involvement of collagen in bone biomineralization is commonly admitted, yet its role remains unclear. Here we show that type I collagen in vitro can initiate and orientate the growth of carbonated apatite mineral in the absence of any other vertebrate extracellular matrix molecules of calcifying tissues. We also show that the collagen matrix influences the structural characteristics on the atomic scale, and controls the size and the three-dimensional distribution of apatite at larger length scales. These results call into question recent consensus in the literature on the need for Ca-rich non-collagenous proteins for collagen mineralization to occur in vivo. Our model is based on a collagen/apatite self-assembly process that combines the ability to mimic the in vivo extracellular fluid with three major features inherent to living bone tissue, that is, high fibrillar density, monodispersed fibrils and long-range hierarchical organization.

Explosive Backpacks in Old Termite Workers

From Science this week comes encapsulation in nature: Neocapritermes taracua workers encapsulate a metalloprotein that reacts with compounds in saliva when the "backpack" capsule bursts.

Abstract

By nature, defensive behavior is risky. In social insects, such behavior is more likely to occur in individuals whose potential for other tasks is diminished. We show that workers of the termite Neocapritermes taracua develop an exceptional two-component suicidal apparatus consisting of copper-containing protein crystals, stored in external pouches, and internal salivary glands. During aggressive encounters, their bodies rupture, and the crystals react with the salivary gland secretion to produce a toxic droplet. Both the amount of defensive substances and the readiness to explode increase with workers’ age, as their food-collecting ability declines.

Can Polymersomes Form Colloidosomes?

 
Kate L. Thompson*,  Pierre Chambon, Robert Verber, and Steven P. Armes*

Hydroxy-functionalized polymersomes (or block copolymer vesicles) were prepared via a facile one-pot RAFT aqueous dispersion polymerization protocol and evaluated as Pickering emulsifiers for the stabilization of emulsions of n-dodecane emulsion droplets in water. Linear polymersomes produced polydisperse oil droplets with diameters of 50 μm regardless of the polymersome concentration in the aqueous phase. Introducing an oil-soluble polymeric diisocyanate cross-linker into the oil phase prior to homogenization led to block copolymer microcapsules, as expected. However, TEM inspection of these microcapsules after an alcohol challenge revealed no evidence for polymersomes, suggesting these delicate nanostructures do not survive the high-shear emulsification process. Thus the emulsion droplets are stabilized by individual diblock copolymer chains, rather than polymersomes. Cross-linked polymersomes (prepared by the addition of ethylene glycol dimethacrylate as a third comonomer) also formed stable n-dodecane-in-water Pickering emulsions, as judged by optical and fluorescence microscopy. However, in this case the droplet diameter varied from 50 to 250 μm depending on the aqueous polymersome concentration. Moreover, diisocyanate cross-linking at the oil/water interface led to the formation of well-defined colloidosomes, as judged by TEM studies. Thus polymersomes can indeed stabilize colloidosomes, provided that they are sufficiently cross-linked to survive emulsification.

Microfluidic Control of the Internal Morphology in Nanofiber-based Macroscopic Cables

Dr. Daisuke Kiriya, Dr. Ryuji Kawano, Dr. Hiroaki Onoe, Prof. Dr. Shoji Takeuchi

Macroscopic cables that consist of assembled nanofibers have been described by S. Takeuchi and co-workers in their Communication (DOI: 10.1002/anie.201202078). The nanofibers in the cables can be oriented parallel or perpendicular to the longitudinal axis by regulating the fluidic velocities of the core and sheath flows in coaxial microfluidic devices. These cables with controlled internal morphology exhibit a difference in their electrical conductivity and mechanical properties depending on their morphology.

Nanoemulsion Composite Microgels for Orthogonal Encapsulation and Release

Harry Z. An^†, Matthew E. Helgeson^†, Patrick S. Doyle^*


Crosslinkable nanoemulsions are combined with flow lithography for the synthesis of structured composite microgels with controlled hydrophobic compartments. The microgels are used to demonstrate a number of motifs for controlled encapsulation and release of active compounds, including small molecules, proteins, and nanoparticles, from a single material platform.  ^{http://onlinelibrary.wiley.com/doi/10.1002/adma.201200214/abstract}