Nicola Hüsing

Membrane Fuel Cell Cathode Catalysts Based on Titanium Oxide Supported Platinum Nanoparticles

The potential of platinum catalysts supported on pure, nitrogen-, or carbon-doped titania for application in the oxygen reduction reaction (ORR), as a cathode catalyst in polymer electrolyte membrane fuel cells, is investigated. The oxide supports are synthesized by using a sol-gel route. Modification with nitrogen and carbon doping is achieved by thermal decomposition of urea and the structure-directing agent P123. Platinum nanoparticles are prepared by reduction of a Pt(IV) salt in ethylene glycol and subsequently immobilized on different support materials. Structural and electronic properties of the support materials and the resulting catalysts are characterized by various methods, including X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. These results and electrochemical characterization of the support materials and platinum nanoparticle catalysts indicate distinct support effects in the catalysts. The electrocatalytic performance of these catalysts in the ORR, as determined in rotating ring disc electrode measurements, is promising. Also here, distinct support effects can be identified. Correlations with the structural/electronic and the electrochemical properties are discussed, as well as the role of metal-support interactions.

Enzyme adsorption-induced activity changes: a quantitative study on TiO2 model agglomerates

BackgroundActivity retention upon enzyme adsorption on inorganic nanostructures depends on different system parameters such as structure and composition of the support, composition of the medium as well as enzyme loading. Qualitative and quantitative characterization work, which aims at an elucidation of the microscopic details governing enzymatic activity, requires well-defined model systems.ResultsVapor phase-grown and thermally processed anatase TiO2 nanoparticle powders were transformed into aqueous particle dispersions and characterized by dynamic light scattering and laser Doppler electrophoresis. Addition of β-galactosidase (β-gal) to these dispersions leads to complete enzyme adsorption and the generation of β-gal/TiO2 heteroaggregates. For low enzyme loadings (~4% of the theoretical monolayer coverage) we observed a dramatic activity loss in enzymatic activity by a factor of 60–100 in comparison to that of the free enzyme in solution. Parallel ATR-IR-spectroscopic characterization of β-gal/TiO2 heteroaggregates reveals an adsorption-induced decrease of the β-sheet content and the formation of random structures leading to the deterioration of the active site.ConclusionsThe study underlines that robust qualitative and quantitative statements about enzyme adsorption and activity retention require the use of model systems such as anatase TiO2 nanoparticle agglomerates featuring well-defined structural and compositional properties.

Potential of nanoparticles for allergen-specific immunotherapy – use of silica nanoparticles as vaccination platform

ABSTRACT Introduction: Allergen-specific immunotherapy is the only curative approach for the treatment of allergies. There is an urgent need for improved therapies, which increase both, efficacy and patient compliance. Novel routes of immunization and the use of more advanced vaccine platforms have gained heightened interest in this field. Areas covered: The current status of allergen-specific immunotherapy is summarized and novel routes of immunization and their challenges in the clinics are critically discussed. The use of nanoparticles as novel delivery system for allergy vaccines is comprehensively reviewed. Specifically, the advantages of silica nanoparticles as vaccine carriers and adjuvants are summarized. Expert opinion: Future allergen-specific immunotherapy will combine engineered hypoallergenic vaccines with novel routes of administration, such as the skin. Due to their biodegradability, and the easiness to introduce surface modifications, silica nanoparticles are promising candidates for tailor-made vaccines. By covalently linking allergens and polysaccharides to silica nanoparticles, a versatile vaccination platform can be designed to specifically target antigen-presenting cells, render the formulation hypoallergenic, and introduce immunomodulatory functions. Combining potent skin vaccination methods, such as fractional laser ablation, with nanoparticle-based vaccines addresses all the requirements for safe and efficient therapy of allergic diseases.

Carbon aerogels with improved flexibility by sphere templating

Mechanically reversible compressible resorcinol–formaldehyde (RF) aerogels can be converted into mechanically reversible compressible carbon aerogels (CA) by carbonization in an inert atmosphere. By incorporation of polystyrene spheres into the RF gels as a sacrificial template, it is possible to create macropores with controlled size within the carbon framework during carbonization. The resulting templated carbon aerogel shows enhanced mechanical flexibility during compression compared to pristine samples. In addition, the presence of hierarchical porosity provides a porous architecture attractive for energy storage applications, such as supercapacitors.

Biologic effects of nanoparticle-allergen conjugates: time-resolved uptake using an in vitro lung epithelial co-culture model of A549 and THP-1 cells

Nanotechnology is a fast growing field and already a multi-billion dollar market with numerous products available for consumers. TiO2 and SiO2 are by mass the most produced nanomaterials and, thus, of particular interest regarding their biological effects upon inhalation – especially in combination with other inhalable biomolecules such as allergens. We investigated the protein-binding capacity of these two nanomaterials and present detailed uptake profiles of protein-conjugated TiO2 or SiO2 nanoparticles (NPs) in A549 lung epithelial and THP-1 macrophage-like cells. TiO2 and SiO2 NPs (both with a hydrodynamic diameter of about 150 nm) are able to bind bovine serum albumin (BSA), green fluorescent protein (GFP) and the major birch pollen allergen Bet v 1 in substantial amounts that suggest protein monolayers around the particles. GFP-conjugated TiO2 and SiO2 NPs were taken up in A549 and THP-1 cells in a time-dependent manner as demonstrated by confocal laser scanning microscopy, flow cytometry and life cell imaging. By the aid of fluorescent proteins (GFP or fluorescently labeled Bet v 1) we found that both, the NPs and the conjugated proteins entered the cells. Using A549/THP-1 co-cultures, we showed that the majority of SiO2 NPs is taken up by THP-1 cells; however, also A549 cells take up significant amounts of particles when co-cultured with THP-1 macrophage-like cells. The here discussed data provide valuable insights into protein (allergen) delivery by NPs at the lung epithelial barrier.