A Pilot Qualitative Investigation of Stakeholders' Experiences and Opinions of Equine Insect Bite Hypersensitivity in England.

Equine insect bite hypersensitivity (IBH), commonly known as sweet itch or summer eczema, is a frustrating recurrent skin disease in the equine industry involving an immune reaction to the bites of Culicoides spp. midges. To investigate the impact of IBH in the field, an exploratory pilot study was conducted with equine stakeholders in one region of central England. Nine semi-structured, face-to-face interviews were conducted with horse owners and an equine veterinarian. The aim was to gain an understanding of experiences with IBH, and to gauge opinions on the value of the various management strategies horse owners use to control IBH. Awareness of IBH was generally high, particularly in those individuals who had previous experience with the condition. Those with previous experience of IBH commented on the significant effect on daily routines, and the associated cost implications. Most participants supported an integrated approach to hypersensitivity management, and this most commonly involved a combination of physical barriers and chemical repellents, but sometimes included feed supplementation. Overall, attitudes towards IBH suggested that the condition is a notable welfare and economic concern for stakeholders, but veterinary involvement tended to only be in more severe cases. Further research is required in the future to improve understanding, management and potential treatment of this condition.

Spray assembled, cross-linked polyelectrolyte multilayer membranes for salt removal.

The present study reports the synthesis of spray-coated cross-linked polyelectrolyte multilayer membranes. Membrane cross-linking was performed using alkyne-azide "click" chemistry, where alkyne and azide functional groups were used to modify the poly(acrylic acid) (PAA) and the poly(allylamine) hydrochloride (PAH) polyelectrolytes. The results demonstrate that deposition at lower ionic strength produced smoother and denser membrane structures. Pore size analysis using neutral poly(ethylene glycol) revealed a decrease in the membrane pore size as the degree of cross-linking was increased, resulting in the membrane rejecting divalent CaCl2 at levels of up to 80%, and 50% rejection of monovalent NaCl. When poly(sodium-4-styrenesulfonate) (PSS) was combined with small amounts of cross-linkable PAA, significant flux increases were observed in the multilayer membranes with no observable reduction in ion rejection.

Polymersome-loaded capsules for controlled release of DNA.

The formation of a novel drug-delivery carrier for the controlled release of plasmid DNA that comprises layer-by-layer polymer capsules subcompartmentalized with pH-sensitive nanometer-sized polymersomes is reported. The amphiphilic diblock copolymer poly(oligoethylene glycol methacrylate)-block-poly(2-(diisopropylamino)ethyl methacrylate) forms polymersomes at physiological pH, but transitions to unimeric polymer chains upon acidification to cellular endocytic pH. These polymersomes can thus release an encapsulated payload in response to a change in pH from physiological to endocytic conditions. Multicomponent layer-by-layer capsules are formed by exploiting the ability of tannic acid to act as an efficient hydrogen-bond donor for both the polymersomes and poly(N-vinyl pyrrolidone) at physiological pH. These capsules show release of a plasmid DNA payload encapsulated within the polymersome subcompartments in response to changes in pH between physiological and endocytic conditions.

Toward therapeutic delivery with layer-by-layer engineered particles.

Layer-by-layer (LbL)-engineered particles have recently emerged as a promising class of materials for applications in biomedicine, with studies progressing from in vitro to in vivo. The versatility of LbL assembly coupled with particle templating has led to engineered particles with specific properties (e.g., stimuli-responsive, high cargo encapsulation efficiency, targeting), thus offering new opportunities in targeted and triggered therapeutic release. This Perspective highlights an important development by Poon et al. on tumor targeting in vivo using LbL-engineered nanoparticles containing a pH-responsive poly(ethylene glycol) (PEG) surface layer. Further, we summarize recent progress in the application of LbL particles in the fields of drug, gene, and vaccine delivery and cancer imaging. Finally, we explore future directions in this field, focusing on the biological processing of LbL-assembled particles.

Nanostructured polymer assemblies formed at interfaces: applications from immobilization and encapsulation to stimuli-responsive release.

In recent years, interfacial properties have been tailored with nanostructured polymer assemblies to generate materials with specific properties and functions for application in diverse fields, including biomaterials, drug delivery, catalysis, sensing, optics and corrosion. This perspective begins with a brief introduction of the assembly techniques that are commonly employed for the synthesis of nanostructured polymer materials, followed by discussions on how the interfaces influence the properties and thus the functionalities of the polymer materials prepared. Applications of the interfacial polymer nanostructures, particularly for the immobilization and encapsulation of cargo, are then reviewed, focusing on stimuli-responsive cargo release from the polymer nanostructured assemblies for controlled delivery applications. Finally, future research directions in these areas are briefly discussed.

Efficient encapsulation of plasmid DNA in pH-sensitive PMPC-PDPA polymersomes: study of the effect of PDPA block length on copolymer-DNA binding affinity.

We report the self-assembly of a series of amphiphilic diblock copolymers comprising a biocompatible, hydrophilic block, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and a pH-sensitive block, poly(2-(diisopropylamino)ethyl methacrylate) (PDPA), into a dispersion of colloidally stable, nanometer-sized polymersomes at physiological pH and salt concentration. The pH-sensitivity of the PDPA block affords the electrostatic interaction of these block copolymers with nucleic acids at endocytic pH, as a result of the protonation of its tertiary amine groups at pH values below its pK(a). Herein we investigate the effect of PDPA block length on the binding affinity of the block copolymer to plasmid DNA.

Diffusion studies of nanometer polymersomes across tissue engineered human oral mucosa.

PURPOSE: To measure the diffusion of nanometer polymersomes through tissue engineered human oral mucosa. METHODS: In vitro models of full thickness tissue engineered oral mucosa (TEOM) were used to assess the penetration properties of two chemically different polymersomes comprising two of block copolymers, PMPC-PDPA and PEO-PDPA. These copolymers self-assemble into membrane-enclosed vesicular structures. Polymersomes were conjugated with fluorescent rhodamine in order to track polymersome diffusion. Imaging and quantification of the diffusion properties were assessed by confocal laser scanning microscopy (CLSM). RESULTS: TEOM is morphologically similar to natural oral mucosa. Using CLSM, both formulations were detectable in the TEOM within 6 h and after 48 h both penetrated up to 80 microm into the TEOM. Diffusion of PMPC-PDPA polymersomes was widespread across the epithelium with intra-epithelial uptake, while PEO-PDPA polymersomes also diffused into the epithelium. CONCLUSIONS: CLSM was found to be an effective and versatile method for analysing the level of diffusion of polymersomes into TEOM. The penetration and retention of PMPC-PDPA and PEO-PDPA polymersomes means they may have potential for intra-epithelial drug delivery and/or trans-epithelial delivery of therapeutic agents.

Synthesis and biological characterisation of novel N-alkyl-deoxynojirimycin alpha-glucosidase inhibitors.

The N-alkylated deoxynojirimycin compound, N-(6'-(4''-azido-2''-nitrophenylamino)hexyl)-1-deoxynojirimycin (6) was synthesised as a potential photoaffinity probe for endoplasmic reticulum (ER) alpha-glucosidases I and II. Surprisingly this compound was a highly potent inhibitor of alpha-glucosidase I (IC(50), 17 nM) in an in vitro assay and proved equally effective at inhibiting cellular ER glucosidases, as determined by a free oligosaccharide (FOS) analysis. A modest library of compounds was synthesised to obtain structure-activity information by variation of the N-alkyl chain length and modifications to the azido-nitrophenyl group. All of these compounds failed to improve on the efficacy of compound 6, but most showed greater enzyme inhibitory potency than N-butyl-deoxynojirimycin (NB-DNJ), a pharmacological agent that has been evaluated for the treatment of several viruses for which infectivity is dependent on host cell glycosylation.

Non-cytotoxic polymer vesicles for rapid and efficient intracellular delivery.

We have recently achieved efficient cytosolic delivery by using pH-sensitive poly(2-(methacryloyloxy)ethylphosphorylcholine)-co-poly(2-(diisopropylamino)ethylmethacrylate) (PMPC-PDPA) diblock copolymers that self-assemble to form vesicles, known as polymersomes, in aqueous solution. It is particularly noteworthy that these diblock copolymers form stable polymersomes at physiological pH but rapidly dissociate below pH 6 to give molecularly-dissolved copolymer chains (unimers). These PMPC-PDPA polymersomes are used to encapsulate nucleic acids for efficient intracellular delivery. Confocal laser scanning microscopy and fluorescence flow cytometry are used to quantify cellular uptake and to study the kinetics of this process. Finally, we examine how PMPC-PDPA polymersomes affect the viability of primary human cells (human dermal fibroblasts (HDF)), paying particular regard to whether inflammatory responses are triggered.

Biocompatible wound dressings based on chemically degradable triblock copolymer hydrogels.

The synthesis of a series of thermo-responsive ABA triblock copolymers in which the outer A blocks comprise poly(2-hydroxypropyl methacrylate) and the central B block is poly(2-(methacryloyloxy)ethyl phosphorylcholine) is achieved using atom transfer radical polymerization. These novel triblock copolymers form thermo-reversible physical gels with critical gelation temperatures and mechanical properties that are highly dependent on the copolymer composition and concentration. TEM studies on dried dilute copolymer solutions indicate the presence of colloidal aggregates, which is consistent with micellar gel structures. This hypothesis is consistent with the observation that incorporating a central disulfide bond within the B block leads to thermo-responsive gels that can be efficiently degraded using mild reductants such as dithiothreitol (DTT) over time scales of minutes at 37 degrees C. Moreover, the rate of gel dissolution increases at higher DTT/disulfide molar ratios. Finally, these copolymer gels are shown to be highly biocompatible. Only a modest reduction in proliferation was observed for monolayers of primary human dermal fibroblasts, with no evidence for cytotoxicity. Moreover, when placed directly on 3D tissue-engineered skin, these gels had no significant effect on cell viability. Thus, we suggest that these thermo-responsive biodegradable copolymer gels may have potential applications as wound dressings.