Regional Differences in Vascular Graft Degradation and Regeneration Contribute to Dilation.

Severe coronary artery disease is often treated with a coronary artery bypass graft using an autologous blood vessel. When this is not available, a commercially available synthetic graft can be used as an alternative but is associated with high failure rates and complications. Therefore, the research focus has shifted toward the development of biodegradable, regenerative vascular grafts that can convert into neoarteries.

Tropoelastin modulates systemic and local tissue responses to enhance wound healing.

Wound healing is facilitated by biomaterials-based grafts and substantially impacted by orchestrated inflammatory responses that are essential to the normal repair process. Tropoelastin (TE) based materials are known to shorten the period for wound repair but the mechanism of anti-inflammatory performance is not known. To explore this, we compared the performance of the gold standard Integra Dermal Regeneration Template (Integra), polyglycerol sebacate (PGS), and TE blended with PGS, in a murine full-thickness cutaneous wound healing study.

Decohesion of a polyolefin overlay from a substrate high density polyethylene layer by impact induced stress waves.

High-density polythene (HDPE) is difficult to separate from food packaging waste for recycling because the packaging occasionally has multilayer plastic labels attached. Solvents are employed in the current separation techniques to remove undesirable layers from HDPE substrates. The possibility of separating HDPE via the impact-delamination phenomenon was explored both theoretically and experimentally.

Rapid Regeneration of a Neoartery with Elastic Lamellae.

Native arteries contain a distinctive intima-media composed of organized elastin and an adventitia containing mature collagen fibrils. In contrast, implanted biodegradable small-diameter vascular grafts do not present spatially regenerated, organized elastin. The elastin-containing structures within the intima-media region encompass the elastic lamellae (EL) and internal elastic lamina (IEL) and are crucial for normal arterial function.

Atom Probe Tomography of Encapsulated Hydroxyapatite Nanoparticles.

Hydroxyapatite nanoparticles (HAP NPs) are important for medicine, bioengineering, catalysis, and water treatment. However, current understanding of the nanoscale phenomena that confer HAP NPs their many useful properties is limited by a lack of information about the distribution of the atoms within the particles. Atom probe tomography (APT) has the spatial resolution and chemical sensitivity for HAP NP characterization, but difficulties in preparing the required needle-shaped samples make the design of these experiments challenging.

Encapsulation by Directed PISA: RAFT-Based Polymer-Vesiculated Pigment for Opacity Enhancement in Paint Films.

A novel method is demonstrated to encapsulate titanium dioxide pigment using directed polymerization-induced self-assembly (PISA) with reversible addition-fragmentation chain-transfer (RAFT) controlled emulsion polymerization. The polymerization is carried out in a batch process in which both styrene (Sty) and the pigment are emulsified using triblock amphiphilic macro-RAFT copolymers as stabilizers. RAFT-controlled chain growth leads to directed lamellar self-assembly, forming polystyrene (PS) shells' encapsulating pigment particles with 100% efficiency.

SPION-Decorated Nanofibers by RAFT-Mediated Free Radical Emulsion Polymerization-Induced Self Assembly.

RAFT-mediated free-radical emulsion polymerization is successfully used to synthesize polystyrene nanofibers using triblock amphiphilic macro-RAFT copolymers as stabilizers. The polymerization is under RAFT control, producing various morphologies from spherical particles, nanofibers, nanoplatelets, and polymer vesicles. Optimum conditions are established for the synthesis of predominantly negatively charged polymer nanofibers.

Aqueous Polymeric Hollow Particles as an Opacifier by Emulsion Polymerization Using Macro-RAFT Amphiphiles.

A robust polymerization technique that enables the surfactant-free aqueous synthesis of a high solid content latex containing polymeric hollow particles is presented. Uniquely designed amphiphilic macro-reversible addition fragmentation chain transfer (RAFT) copolymers were used as sole stabilizers for monomer emulsification as well as for free-radical emulsion polymerization. The polymerization was found to be under RAFT control, generating various morphologies from spherical particles, wormlike structures to polymer vesicles.

Steric Stabilization of γ-FeO Superparamagnetic Nanoparticles in a Hydrophobic Ionic Liquid and the Magnetorheological Behavior of the Ferrofluid.

Hydrophobic ionic liquid ferrofluids (ILFFs) are studied for use in electrospray thrusters for microsatellite propulsion under nonatmospheric and in high-temperature environments. We synthesized a hydrophobic ILFF by dispersing sterically stabilized γ-FeO nanoparticles (NPs) in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A diblock copolymer, C4-RAFT-AA-DEAm, was synthesized to facilitate multipoint bidentate anchoring to the NP through the acrylic acid block.

Biodistribution and Clearance of Stable Superparamagnetic Maghemite Iron Oxide Nanoparticles in Mice Following Intraperitoneal Administration.

Nanomedicine is an emerging field with great potential in disease theranostics. We generated sterically stabilized superparamagnetic iron oxide nanoparticles (s-SPIONs) with average core diameters of 10 and 25 nm and determined the in vivo biodistribution and clearance profiles. Healthy nude mice underwent an intraperitoneal injection of these s-SPIONs at a dose of 90 mg Fe/kg body weight.

Endogenous fibrinolysis facilitates clot retraction in vivo.

Clot retraction refers to the process whereby activated platelets transduce contractile forces onto the fibrin network of a thrombus, which over time increases clot density and decreases clot size. This process is considered important for promoting clot stability and maintaining blood vessel patency. Insights into the mechanisms regulating clot retraction at sites of vascular injury have been hampered by a paucity of in vivo experimental models.

Tunable and noncytotoxic PET/SPECT-MRI multimodality imaging probes using colloidally stable ligand-free superparamagnetic iron oxide nanoparticles.

Physiologically stable multimodality imaging probes for positron emission tomography/single-photon emission computed tomography (PET/SPECT)-magnetic resonance imaging (MRI) were synthesized using the superparamagnetic maghemite iron oxide (γ-FeO) nanoparticles (SPIONs). The SPIONs were sterically stabilized with a finely tuned mixture of diblock copolymers with either methoxypolyethylene glycol (MPEG) or primary amine NH end groups. The radioisotope for PET or SPECT imaging was incorporated with the SPIONs at high temperature.

Durable Superhydrophobic Surfaces via Spontaneous Wrinkling of Teflon AF.

We report the fabrication of both single-scale and hierarchical superhydrophobic surfaces, created by exploiting the spontaneous wrinkling of a rigid Teflon AF film on two types of shrinkable plastic substrates. Sub-100 nm to micrometric wrinkles were reproducibly generated by this simple process, with remarkable control over the size and hierarchy. Hierarchical Teflon AF wrinkled surfaces showed extremely high water repellence (contact angle 172°) and very low contact angle hysteresis (2°), resulting in droplets rolling off the surface at tilt angles lower than 5°.

Preparation of Inert Polystyrene Latex Particles as MicroRNA Delivery Vectors by Surfactant-Free RAFT Emulsion Polymerization.

We present the preparation of 11 nm polyacrylamide-stabilized polystyrene latex particles for conjugation to a microRNA model by surfactant-free RAFT emulsion polymerization. Our synthetic strategy involved the preparation of amphiphilic polyacrylamide-block-polystyrene copolymers, which were able to self-assemble into polymeric micelles and "grow" into polystyrene latex particles. The surface of these sterically stabilized particles was postmodified with a disulfide-bearing linker for the attachment of the microRNA model, which can be released from the latex particles under reducing conditions.

The interaction of sterically stabilized magnetic nanoparticles with fresh human red blood cells.

Sterically stabilized superparamagnetic iron oxide nanoparticles (SPIONs) were incubated with fresh human erythrocytes (red blood cells [RBCs]) to explore their potential application as magnetic resonance imaging contrast agents. The chemical shift and linewidth of (133)Cs(+) resonances from inside and outside the RBCs in (133)Cs nuclear magnetic resonance spectra were monitored as a function of time. Thus, we investigated whether SPIONs of two different core sizes and with three different types of polymeric stabilizers entered metabolically active RBCs, consuming glucose at 37°C.

Self-assembling array of magnetoelectrostatic jets from the surface of a superparamagnetic ionic liquid.

Electrospray is a versatile technology used, for example, to ionize biomolecules for mass spectrometry, create nanofibers and nanowires, and propel spacecraft in orbit. Traditionally, electrospray is achieved via microfabricated capillary needle electrodes that are used to create the fluid jets. Here we report on multiple parallel jetting instabilities realized through the application of simultaneous electric and magnetic fields to the surface of a superparamagnetic electrically conducting ionic liquid with no needle electrodes.

Premature detonation of an NH₄NO₃ emulsion in reactive ground.

When NH4NO3 emulsions are used in blast holes containing pyrite, they can exothermally react with pyrite, causing the emulsion to intensively heat and detonate prematurely. Such premature detonations can inflict fatal and very costly damages. The mechanism of heating of the emulsions is not well understood though such an understanding is essential for designing safe blasting.

Ultrasmall superparamagnetic iron oxide nanoparticle prelabelling of human neural precursor cells.

Stem cells prelabelled with iron oxide nanoparticles can be visualised using magnetic resonance imaging (MRI). This technique allows for noninvasive long-term monitoring of migration, integration and stem cell fate following transplantation into living animals. In order to determine biocompatibility, the present study investigated the biological impact of introducing ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) into primary human fetal neural precursor cells (hNPCs) in vitro.

The composition and end-group functionality of sterically stabilized nanoparticles enhances the effectiveness of co-administered cytotoxins.

Diffusion of active cytotoxic agents throughout an entire solid tumour is a particular challenge to successful drug delivery. Here we show the simple and robust generation of non-toxic, 10-15 nm superparamagnetic iron oxide nanoparticles (SPIONs) that have been sterically stabilized by either 100% anionic or 100% cationic or 100% neutral end-functionalized steric stabilizers or by novel combinations of cationic and neutral end-functionalized polymer. When these nanoparticles were co-administered with various anti-cancer drugs, a significant increase in the diffusion and effectiveness of the cytotoxin in a 3-dimensional model of a solid tumour was shown for specific combinations of surface functionality and cytotoxin.

Phase behavior of amphiphilic diblock co-oligomers with nonionic and ionic hydrophilic groups.

The synthesis of a series of co-oligomer amphiphiles by RAFT and their self-assembly behavior in water is described. These novel amphiphiles, comprised of styrene, butyl acrylate, and alkyl hydrophobes together with ionic acrylic acid and nonionic hydroxyethylacrylate hydrophilic moieties and with a total degree of polymerization from 5 to 17, represent a new class of small-molecule surfactants that can be formed from the immense potential library of all polymerizable monomers. Examples of micellar solutions and discrete cubic, hexagonal, lamellar, and inverted hexagonal lyotropic phases, as well as vesicle dispersions and coexisting lamellar phases, are reported and characterized by small-angle scattering.

Stable and water-tolerant ionic liquid ferrofluids.

Ionic liquid ferrofluids have been prepared containing both bare and sterically stabilized 8-12 nm diameter superparamagnetic iron oxide nanoparticles, which remain stable for several months in both protic ethylammonium and aprotic imidazolium room-temperature ionic liquids. These ferrofluids exhibit spiking in static magnetic fields similar to conventional aqueous and nonaqueous ferrofluids. Ferrofluid stability was verified by following the flocculation and settling behavior of dilute nanoparticle dispersions.

Optimized steric stabilization of aqueous ferrofluids and magnetic nanoparticles.

The preparation and properties of an aqueous ferrofluid consisting of a concentrated (>65 wt %) dispersion of sterically stabilized superparamagnetic, iron oxide (maghemite) nanoparticles stable for several months at high ionic strength and over a broad pH range is described. The 6-8 nm diameter nanoparticles are individually coated with a short poly(acrylic acid)-b-poly(acrylamide) copolymer, designed to form the thinnest possible steric stabilizing layer while remaining strongly attached to the iron oxide surface over a wide range of nanoparticle concentrations. Thermogravimetric analysis yields an iron oxide content of 76 wt % in the dried particles, consistent with a dry polymer coating of approximately 1 nm in thickness, while the poly(acrylamide) chain length indicated by electrospray mass spectrometry is consistent with the 4-5 nm increase in the hydrodynamic radius observed by light scattering when the poly(acrylamide) stabilizing chains are solvated.

Chain Transfer to Polymer and Branching in Controlled Radical Polymerizations of n-Butyl Acrylate.

Chain transfer to polymer (CTP) in conventional free-radical polymerizations (FRPs) and controlled radical polymerizations (ATRP, RAFT and NMP) of n-butyl acrylate (BA) has been investigated using (13) C NMR measurements of branching in the poly(n-butyl acrylate) produced. The mol-% branches are reduced significantly in the controlled radical polymerizations as compared to conventional FRPs. Several possible explanations for this observation are discussed critically and all except one refuted.