Rhiannon P. Kuchel

An Efficient and Highly Versatile Synthetic Route to Prepare Iron Oxide Nanoparticles/Nanocomposites with Tunable Morphologies

We report a versatile synthetic method for the in situ self-assembly of magnetic-nanoparticle-functionalized polymeric nanomorphologies, including spherical micelles and rod-like and worm-like micelles and vesicles. Poly(oligoethylene glycol methacrylate)-block-(methacrylic acid)-block-poly(styrene) (POEGMA-b-PMAA-b-PST) triblock copolymer chains were simultaneously propagated and self-assembled via a polymerization-induced self-assembly (PISA) approach. Subsequently, the carboxylic acid groups in the copolymers were used to complex an iron ion (Fe(II)/Fe(III)) mixture. Iron oxide nanoparticles were then formed in the central block, within the polymeric nanoparticles, via alkaline coprecipitation of the iron(II) and (III) salts. Nanoparticle morphologies, particle sizes, molecular weights, and chemical structures were then characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), size exclusion chromatography (SEC), and (1)H NMR measurements. TEM micrographs showed that the average size of the magnetic nanoparticles was ∼7 nm at the hydrophobic/hydrophilic nexus contained within the nanoparticles. In addition, XRD was used to confirm the formation of iron oxide nanoparticles. Importantly, the polymeric nanoparticle morphologies were not affected by the coprecipitation of the magnetic nanoparticles. The hybrid nanoparticles were then evaluated as negative MRI contrast agents, displaying remarkably high transverse relaxivities (r2, greater than 550 mM(-1) s(-1) at 9.4 T); a result, that we hypothesize, ensues from iron oxide nanoparticle clustering at the hydrophobic-hydrophilic interface. This simple synthetic procedure is highly versatile and produces nanocarriers of tunable size and shape with high efficacy as MRI contrast agents and potential utility as theranostic delivery vectors.

Extracellular Vesicles Provide a Means for Tissue Crosstalk during Exercise

Exercise stimulates the release of molecules into the circulation, supporting the concept that inter-tissue signaling proteins are important mediators of adaptations to exercise. Recognizing that many circulating proteins are packaged in extracellular vesicles (EVs), we employed quantitative proteomic techniques to characterize the exercise-induced secretion of EV-contained proteins. Following a 1-hr bout of cycling exercise in healthy humans, we observed an increase in the circulation of over 300 proteins, with a notable enrichment of several classes of proteins that compose exosomes and small vesicles. Pulse-chase and intravital imaging experiments suggested EVs liberated by exercise have a propensity to localize in the liver and can transfer their protein cargo. Moreover, by employing arteriovenous balance studies across the contracting human limb, we identified several novel candidate myokines, released into circulation independently of classical secretion. These data identify a new paradigm by which tissue crosstalk during exercise can exert systemic biological effects.

Polymerization induced self-assembly: tuning of morphology using ionic strength and pH

Investigations of RAFT dispersion polymerization-induced self-assembly (PISA) of 2-hydroxypropyl methacrylate (HPMA) in water/methanol at 60 °C using a cationically charged macroRAFT agent as the stabilizer block, namely P(N,N-diethylaminoethyl methacrylate)-stat-poly((ethylene glycol) methyl ether methacrylate) (PDEAEMA-stat-PEGMA), have been conducted with a view to tune particle morphologies by manipulation of the pH and the ionic strength. Above the LCST (45 °C) of (PDEAEMA-stat-PEGMA), the system can only be conducted as a dispersion polymerization at sufficiently low pH such that the stabilizer block is sufficiently protonated to ensure solubility in the continuous phase. It is demonstrated (reported in the form of an extensive morphology diagram) that a range of morphologies including spherical particles, rods and vesicles can be accessed by adjustment of the pH (via addition of HCl) and the ionic strength (via the concentration of NaCl). A decrease in the charge density of the coronal stabilizer layer via an increase in the pH (less protonation) shifts the system towards higher order morphologies. At a given pH, an increase in ionic strength leads to more extensive charge screening, thus allowing formation of higher order morphologies.

Infectious microbial diseases and host defense responses in Sydney rock oysters

Aquaculture has long been seen as a sustainable solution to some of the worlds growing food shortages. However, experience over the past 50 years indicates that infectious diseases caused by viruses, bacteria, and eukaryotes limit the productivity of aquaculture. In extreme cases, these types of infectious agents threaten the viability of entire aquaculture industries. This article describes the threats from infectious diseases in aquaculture and then focuses on one example (QX disease in Sydney rock oysters) as a case study. QX appears to be typical of many emerging diseases in aquaculture, particularly because environmental factors seem to play a crucial role in disease outbreaks. Evidence is presented that modulation of a generic subcellular stress response pathway in oysters is responsible for both resistance and susceptibility to infectious microbes. Understanding and being able to manipulate this pathway may be the key to sustainable aquaculture.

A new paradigm in polymerization induced self-assembly (PISA): Exploitation of “non-living” addition–fragmentation chain transfer (AFCT) polymerization

Polymerization-induced self-assembly (PISA) is conducted based on “non-living” radical dispersion polymerization in the form of addition–fragmentation chain transfer (AFCT) polymerization. AFCT polymerization of benzyl methacrylate in ethanol using a polymeric AFCT agent comprising poly(ethylene glycol) methyl ether methacrylate generates an amphiphilic copolymer which subsequently self-assembles into various morphologies. This novel approach may expand the scope of PISA for synthesis of sulfur-free polymeric (nano)particles.

Polymer-inorganic hybrid nanoparticles of various morphologies via polymerization-induced self assembly and sol–gel chemistry

The preparation of polymer-silica hybrid nanoparticles of various morphologies is reported. As a first step, polymer nanoparticles were synthesized using an alkoxysilane-functional methacrylic macroRAFT agent. Two different alkoxysilane-containing monomers, 3-(trimethoxysilyl)propyl methacrylate and 3-(triisopropoxysilyl)propyl methacrylate, were used to prepare the solvophilic block for the subsequent polymerization-induced self assembly (PISA) of benzyl methacrylate in ethanol. Various particle morphologies, such as vesicles, spheres and rods could be formed. The primary factor governing nanoparticle shape was the nature of the macroRAFT agent, with the bulkier triisopropoxysilyl group yielding spherical structures; the smaller trimethoxysilyl group allowed for morphological transitions to occur as the length of the solvophobic block was increased. In many cases, the resultant nanoparticle dispersion was highly monodisperse. The influence of RAFT agent type was also studied. The presence of reactive alkoxysilane groups at the particle surface enabled a silica shell to be grown from the surface via condensation of tetraethylorthosilicate (TEOS) in a controlled fashion, resulting in the simple preparation of hybrid nanoparticles.

Exploring the potential of linear polymer structures for the synthesis of fluorescent gold nanoclusters

In this study, fluorescent gold nanoclusters (AuNCs) were synthesized via the one-pot reduction of gold ions (Au3+) in the presence of thiolated copolymers. Well-defined copolymers, which are comprised of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(acetylthio)ethyl methacrylate (AcSEMA) monomers in either a block or random structure, were prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization. Following deprotection of the AcSEMA thioester pendant group to yield a thiol, the formation of gold nanoclusters was performed at various relative molar concentrations of thiol to gold ions in order to investigate the effect on the fluorescent properties. Random copolymer stabilized gold nanoclusters (R@AuNCs) displayed higher emission intensity in comparison to block copolymer stabilized gold nanoclusters (B@AuNCs). In aqueous media, the hydrodynamic diameter of B@AuNCs (10.4–13.4 nm) were relatively larger compared to the R@AuNCs (5.9–6.6 nm) as determined by dynamic light scattering (DLS). However, the AuNCs cores were estimated to be similar in size according to the Jellium model (≅0.49 nm, ∼Au25), indicating the negligible effect of different polymer structure on the size of the fluorescent AuNCs core. Interestingly, these nanoclusters displayed linear temperature-dependent fluorescence emission intensity (≅0.7% °C−1) which may be important in biosensing applications.

Cold adaptation of the Antarctic haloarchaea Halohasta litchfieldiae and Halorubrum lacusprofundi

Summary Halohasta litchfieldiae represents ∼ 44% and Halorubrum lacusprofundi ∼ 10% of the hypersaline, perennially cold (≥ −20°C) Deep Lake community in Antarctica. We used proteomics and microscopy to define physiological responses of these haloarchaea to growth at high (30°C) and low (10 and 4°C) temperatures. The proteomic data indicate that both species responded to low temperature by modifying their cell envelope including protein N‐glycosylation, maintaining osmotic balance and translation initiation, and modifying RNA turnover and tRNA modification. Distinctions between the two species included DNA protection and repair strategies (e.g. roles of UspA and Rad50), and metabolism of glycerol and pyruvate. For Hrr. lacusprofundi, low temperature led to the formation of polyhydroxyalkanoate‐like granules, with granule formation occurring by an unknown mechanism. Hrr. lacusprofundi also formed biofilms and synthesized high levels of Hsp20 chaperones. Hht. litchfieldiae was characterized by an active CRISPR system, and elevated levels of the core gene expression machinery, which contrasted markedly to the decreased levels of Hrr. lacusprofundi. These findings greatly expand the understanding of cellular mechanisms of cold adaptation in psychrophilic archaea, and provide insight into how Hht. litchfieldiae gains dominance in Deep Lake.

Synthesis and characterisation of gradient polymeric nanoparticles

In this communication, we report the successful synthesis of gradient morphology nanoparticles composed of poly(styrene-co-methyl methacrylate) and their characterisation using X-Ray Photoelectron Spectroscopy (XPS). Gradient morphology latexes are of particular interest in the coatings industry as they are formulated with reduced volatile organic compound content and exhibit high gloss.

Synthesis of microcapsules using inverse emulsion periphery RAFT polymerization via SPG membrane emulsification

Hollow particles have the potential for a broad range of applications, but most specifically drug delivery. However, their synthesis can be tedious, requiring techniques such as high energy input or a sacrificial template. Furthermore, loading the final capsules with drugs, catalysts or any other compound is often associated with a low loading efficiency. In this study, we have explored the use of “Shirasu Porous Glass (SPG)” membrane emulsification to create a wide size range of water droplets stabilized with an amphiphilic block copolymer. Polymeric capsules were subsequently created via inverse emulsion periphery RAFT polymerization (IEPP). By changing the pore size of the SPG membrane (0.2–3 μm), we have succeeded in controlling the polymeric microcapsule size from submicron to tens of microns. In addition to this, the process allowed simultaneous and efficient encapsulation of water-soluble compounds such as proteins.