Novel injectable gallium-based self-setting glass-alginate hydrogel composite for cardiovascular tissue engineering.

Composite biomaterials offer a new approach for engineering novel, minimally-invasive scaffolds with properties that can be modified for a range of soft tissue applications. In this study, a new way of controlling the gelation of alginate hydrogels using Ga-based glass particles is presented. Through a comprehensive analysis, it was shown that the setting time, mechanical strength, stiffness and degradation properties of this composite can all be tailored for various applications. Specifically, the hydrogel generated through using a glass particle, wherein toxic aluminium is replaced with biocompatible gallium, exhibited enhanced properties. The material's stiffness matches that of soft tissues, while it displays a slow and tuneable gelation rate, making it a suitable candidate for minimally-invasive intra-vascular injection. In addition, it was also found that this composite can be tailored to deliver ions into the local cellular environment without affecting platelet adhesion or compromising viability of vascular cells in vitro.

Size-Controlled Nanoparticle Clusters of Narrow Size-Polydispersity Formed Using Multiple Particle Types Through Competitive Stabilizer Desorption to a Liquid-Liquid Interface.

A novel colloidal approach is presented for preparing fully dispersed nanoparticle (NP) assemblies (clusters) of narrow size-polydispersity over a wide range of sizes through irreversible depletion of stabilizing ligands onto a liquid-liquid interface. Unusually, the relative monodispersity of the assemblies continuously improves throughout the process. A detailed kinetics study into the assembly of iron oxide NP clusters shows that the assembly rate decreases with NP concentration, pinpointing the role of the interface in size focusing. A new protocol for identifying initial conditions that enable controlled assembly is described, which allows extension of the approach to multiple NP types, opening up a general route to colloidally processed materials. The process uses cheap materials, it is reproducible, robust, and scaleable, and it allows for selection of both particle and cluster size. In the case of assemblies of magnetic iron oxide NPs, these advantages enable tuning of the magnetic properties of the assemblies for applications such as magnetically targetable MRI-trackable agents in biomedicine.

Monodisperse magnetic nanoparticle assemblies prepared at scale by competitive stabiliser desorption.

We report a scalable and reproducible method to assemble magnetic nanoparticle clusters from oleic acid stabilised iron oxide nanoparticles. By controlling the surface coverage of oleic acid on the nanoparticle surface we have achieved controlled nanoparticle assembly following exposure of the suspension to a substrate layer of cyanopropyl-modified silica which competes for the ligand. The clusters can be formed reproducibly and their final size can be selected over a range covering almost two orders of magnitude. Most unusually, the relative monodispersity of the cluster suspension is improved compared to the starting nanoparticle suspension, and the yield is close to 100%. Interestingly, we find that the kinetics of assembly is not altered by scaling up, which is surprising for a complex process involving molecular transport. Kinetic studies provided mechanistic insight into the process, and suggested general requirements for controlled assembly of other nanoparticle types.

pH control of the electrostatic binding of gold and iron oxide nanoparticles to tobacco mosaic virus.

We report the binding of nanoparticles (NPs) to wild type (unmodified) tobacco mosaic virus (TMV). The viruses are simply mixed with citrate-coated, negatively charged gold and iron oxide nanoparticles (IONPs) in acidic solution. This results in TMV decorated along its whole length by the respective particles. Such a decoration usually requires chemical modification or mutation of TMV (e.g., cysteine residues), but here we simply reduce TMV's natural negative charge by protonation. The particles are protonated to a much smaller extent. This charge-based mechanism does not operate for neutral particles.

Water-soluble superparamagnetic magnetite nanoparticles with biocompatible coating for enhanced magnetic resonance imaging.

Ultrasmall superparamagnetic Fe(3)O(4) nanoparticles (USIRONs) were synthesized by a novel, easily scalable chemical reduction of colloidal iron hydroxide under hydrothermal conditions. The average crystallite size (5.1 ± 0.5 nm) and good crystallinity of the samples were supported by HR-TEM analysis and the saturation magnetization value (47 emu g(-1)). Vitamin C, used as a chemical reducing agent, also served as a capping agent in the oxidized form (dehydroascorbic acid, DHAA) to impart nanoparticles with exceptional solubility and stability in water, PBS buffer, and cell culture medium. Detailed physicochemical analysis of the USIRON suspensions provided insight into the magnetic ordering phenomena within the colloid, arising from the formation of uniform clusters displaying a hydrodynamic size of 41 nm. Phantom experiments on the contrast agent (clinical 3 T MRI scanner) revealed an enhanced r(2)/r(1) ratio of 36.4 (r(1)= 5 s(-1) mM(-1) and r(2)= 182 s(-1) mM(-1)) when compared to the clinically approved agents. The potential of the DHAA-Fe(3)O(4) nanoparticles as negative contrast agents for MRI with optimal hydrodynamic size for extended blood circulation times was confirmed by strong contrast observed in T(2)- and T(2)*-weighted images. The cell tests performed with primary human immune-competent cells confirmed the excellent biocompatibility of USIRONs.