Colloid-matrix assemblies in regenerative medicine

The development of tissue engineering scaffolds has focused on mimicking the natural biochemical and biophysical environment of the extracellular matrix (ECM). In this review, we describe a variety of strategies aimed at reproducing and also simplifying the ECM. Despite the progress that has been made, the degree of complexity that needs to be incorporated into these scaffolds is still not known. We begin by describing the ECM and its biological functions followed by outlining current efforts to engineer ECMs with both natural and synthetic polymers. We then focus on colloidal particles as potential artificial ECM components that could increase the complexity as modular building blocks. Drawing from examples from the literature we present the broad utility of colloids and describe how these applications could be useful in the development of ECM mimetic systems.     

Rapid synthesis of aurones under mild conditions using a combination of microwaves and deep eutectic solvents

The combination of microwave heating and the deep eutectic solvent formed from choline chloride and urea has resulted in a new, essentially neutral, yet rapid method for the synthesis of a wide range of aurone derivatives. While isolated yields remain somewhat variable, in virtually every case, a significant increase in yield has been observed on going from conventional thermal heating to microwave heating. In addition, some compounds inaccessible using prior methods have become reproducibly available using this modification. Further application of the combination of DES and microwave heating is expected to be highly promising and of general utility.     

Analysis of oligomeric peroxides in synthetic triacetone triperoxide samples by tandem mass spectrometry

Oligomeric peroxides formed in the synthesis of triacetone triperoxide (TATP) have been analyzed by mass spectrometry utilizing both electrospray ionization (ESI) and chemical ionization (CI) to form sodiated adducts (by ESI) and ammonium adducts (by CI and ESI). Tandem mass spectrometry and deuterium isotopic labeling experiments have been used to elucidate the collision‐induced dissociation (CID) mechanisms for the adducts. The CID mechanisms differ for the sodium and ammonium adducts and vary with the size of the oligoperoxide. The sodium adducts of the oligoperoxides, H[OOC(CH₃)₂]_nOOH, do not cyclize under CID, whereas the ammonium adducts of the smaller oligoperoides (n < 6) do form the cyclic peroxides under CID. Larger oligoperoxide adducts with both sodium and ammonium undergo dissociation through cleavage of the backbone under CID to form acyl‐ and hydroperoxy‐terminated oligomers of the general form CH₃C(O)[OOC(CH₃)₂]_xOOH, where x is an integer less than the original oligoperoxide degree of oligomerization. The oligoperoxide distribution is shown to vary batch‐to‐batch in the synthesis of TATP and the post‐blast distribution differs slightly from the distribution in the uninitiated material. The oligoperoxides are shown to be decomposed under gentle heating. Copyright © 2009 John Wiley & Sons, Ltd.     

A review of nanowire growth promoted by alloys and non-alloying elements with emphasis on Au-assisted III–V nanowires

Seed particles of elements or compounds which may or may not form alloys are now used extensively in promoting well-controlled nanowire growth. The technology has evolved following the well-known Vapour–Liquid–Solid (VLS) model which was developed over 40 years ago. This model indicates that a liquid alloy is formed from the seed particle and the growth precursor(s), resulting in crystal growth by precipitation from a supersaturated solution. The enhanced growth rate compared to the bulk growth from the vapour is typically attributed to preferential decomposition of precursor materials at or near the particle surface. Recently, however, there has been much interest in further developing this model, which was developed for Au-assisted Si whiskers (with diameter on the micrometre scale), in order to generally describe particle-assisted growth on the nanoscale using a variety of materials and growth systems. This review discusses the current understanding of particle-assisted nanowire growth. The aim is first to give an overview of the historical development of the model, with a discussion of potential growth mechanisms. In particular, the enhancement of growth rate in one dimension due to preferential deposition at the particle–wire interface will be discussed. Then, the particular example of III–V nanowires grown by metal–organic vapour phase epitaxy using Au particles will be revised, with details of the various growth processes involved in this system. The aim of this review is not to provide a conclusive answer to the question of why nanowires grow from seed particle alloys, but to describe the progress made towards this goal of a unified theory of growth, and to clarify the current standing of the question.