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Functionalized Surfaces and Interactions with Biomolecules
No full textOne of the first crucial reactions of any artificial material exposed to biological environments is the materials' surface interaction with biomolecules. The interaction is widely dependent on the material properties and the chemical functionalities and structures exposed on its surface. Tailoring the surface properties of ceramics and other materials is a manner to guide biomolecular interactions, to prevent or reduce them, to specifically evoke them, and hence use them to stimulate a certain subsequent reaction. This provides an opportunity to also control the interactions and tune materials by surface functionalization for a variety of applications. In this chapter, we give a concise overview of the most crucial principles that govern the complex biomolecule-surface interactions focusing on fundamental forces and which structures from materials, biomolecules, and their environments influence the interaction in complex biological media. A special focus is on surface functionalizations for ceramic substrates that can be used to tune biomolecular interactions with the material surfaces as an important design principle for materials in various applications in biomedical, environmental, and pharmaceutical areas
PROCESS FOR OBTAINING A POROUS MATERIAL FROM POWDER MATERIALS, A POROUS MATERIAL AND USE THEREOF FOR THE CAPTURE OF ATMOSPHERIC PARTICULATE MATTER AND ORGANIC CONTAMINANTS
No full textControlling Mixed-Protein Adsorption Layers on Colloidal Alumina Particles by Tailoring Carboxyl and Hydroxyl Surface Group Densities
No full textWe show that different ratios of bovine serum albumin (BSA) and lysozyme (LSZ) can be achieved in a mixed protein adsorption layer by tailoring the amounts of carboxyl (-COOH) and aluminum hydroxyl (AlOH) groups on colloidal alumina particles (d(50) approximate to 180 nm). The particles are surface-functionalized with -COOH groups, and the resultant surface chemistry, including the remaining AlOH groups, is characterized and quantified using elemental analysis, zeta potential measurements, acid base titration, IR spectroscopy, electron microscopy, nitrogen adsorption, and dynamic light scattering. BSA and LSZ are subsequently added to the particle suspensions, and protein adsorption is monitored by in situ zeta potential measurements while being quantified by UV spectroscopy and gel electrophoresis. A comparison of single-component and sequential protein adsorption reveals that BSA and LSZ have specific adsorption sites: BSA adsorbs primarily via AlOH groups, whereas LSZ adsorbs only via -COOH groups (1-2 -COOH groups on the particle surface is enough to bind one LSZ molecule). Tailoring such groups on the particle surface allows control of the composition of a mixed BSA and LSZ adsorption layer. The results provide further insight into how particle surface chemistry affects the composition of protein adsorption layers on colloidal particles and is valuable for the design of such particles for biotechnological and biomedical applications
Controlling protein-particle adsorption by surface tailoring colloidal alumina particles with sulfonate groups
No full textIn this study, we demonstrate the control of protein adsorption by tailoring the sulfonate group density on the surface of colloidal alumina particles. The colloidal alumina (d(50) = 179 +/- 8 nm) is first accurately functionalized with sulfonate groups (SO3H) in densities ranging from 0 to 4.7 SO3H nm(-2). The zeta potential, hydrophilic/hydrophobic properties, particle size, morphology, surface area and elemental composition of the functionalized particles are assessed. The adsorption of three model proteins, bovine serum albumin (BSA), lysozyme (LSZ) and trypsin (TRY), is then investigated at pH 6.9 +/- 0.3 and an ionic strength of 3 mM. Solution depletion and zeta potential experiments show that BSA, LSZ and TRY adsorption is strongly affected by the SO3H surface density rather than by the net zeta potential of the particles. A direct correlation between the SO3H surface density, the intrinsic protein amino acid composition and protein adsorption is observed. Thus a continuous adjustment of the protein adsorption amount can be achieved between almost no coverage and a theoretical monolayer by varying the density of SO3H groups on the particle surface. These findings enable a deeper understanding of protein-particle interactions and, moreover, support the design and engineering of materials for specific biotechnology, environmental technology or nanomedicine applications. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Functionalized ceramics for biomedical, biotechnological and environmental applications
No full textSurface functionalization has become of paramount importance and is considered a fundamental tool for the development and design of countless devices and engineered systems for key technological areas in biomedical, biotechnological and environmental applications. In this review, surface functionalization strategies for alumina, zirconia, titania, silica, iron oxide and calcium phosphate are presented and discussed. These materials have become particularly important concerning the aforementioned applications, being not only of great academic, but also of steadily increasing human and commercial, interest. In this review, special emphasis is given to their use as biomaterials, biosensors, biological targets, drug delivery systems, implants, chromatographic supports for biomolecule purification and analysis, and adsorbents for toxic substances and pollutants. The objective of this review is to provide a broad picture of the enormous possibilities offered by surface functionalization and to identify particular challenges regarding surface analysis and characterization. (c) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Fluorescence labeling of colloidal core-shell particles with defined isoelectric points for in vitro studies
No full textIn the light of in vitro nanotoxicological studies fluorescence labeling has become standard for particle localization within the cell environment. However, fluorescent labeling is also known to significantly alter the particle surface chemistry and therefore potentially affect the outcome of cell studies. Hence, fluorescent labeling is ideally carried out without changing, for example, the isoelectric point. A simple and straightforward method for obtaining fluorescently labeled spherical metal oxide particles with well-defined isoelectric points and a narrow size distribution is presented in this study. Spherical amorphous silica (SiO2, 161 nm diameter) particles were used as the substrate material and were coated with silica, alumina (Al2O3), titania (TiO2), or zirconia (ZrO2) using sol-gel chemistry. Fluorescent labeling was achieved by directly embedding rhodamine 6G dye in the coating matrix without affecting the isoelectric point of the metal oxide coatings. The coating quality was confirmed by high resolution transmission electron microscopy, energy filtered transmission electron microscopy and electrochemical characterization. The coatings were proven to be stable for at least 240 h under different pH conditions. The well-defined fluorescent particles can be directly used for biomedical investigations, e.g. elucidation of particle-cell interactions in vitro. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Adsorption and Orientation of the Physiological Extracellular Peptide Glutathione Disulfide on Surface Functionalized Colloidal Alumina Particles
No full textUnderstanding the interrelation between surface chemistry of colloidal particles and surface adsorption of biomolecules is a crucial prerequisite for the design of materials for biotechnological and nanomedical applications. Here, we elucidate how tailoring the surface chemistry of colloidal alumina particles (d(50) = 180 nm) with amino (-NH2), carboxylate (-COOH), phosphate (-PO3H2) or sulfonate (-SO3H) groups affects adsorption and orientation of the model peptide glutathione disulfide (GSSG). GSSG adsorbed on native, -NH2-functionalized, and -SO3H-functionalized alumina but not on -COOH- and -PO3H2-functionalized particles. When adsorption occurred, the process was rapid (<= 5 min), reversible by application of salts, and followed a Langmuir adsorption isotherm dependent on the particle surface functionalization and zeta potential. The orientation of particle bound GSSG was assessed by the release of glutathione after reducing the GSSG disulfide bond and by zeta potential measurements. GSSG is likely to bind via the carboxylate groups of one of its two glutathionyl (GS) moieties onto native and -NH2-modified alumina, whereas GSSG is suggested to bind to -SO3H-modified alumina via the primary amino groups of both GS moieties. Thus, GSSG adsorption and orientation can be tailored by varying the molecular composition of the particle surface, demonstrating a step toward guiding interactions of biomolecules with colloidal particles
Physicochemical properties and biodegradability of organically functionalized colloidal silica particles in aqueous environment
No full textEngineered sub-micron particles are being used in many technical applications, leading to an increasing introduction into the aquatic environment. Only a few studies have dealt with the biodegradability of non-functionalized organic particles. In fact the knowledge of organically surface functionalized colloids is nearly non-existent. We have investigated the biodegradability of organically surface functionalized silica (SiO2) particles bearing technically relevant groups such as amino-, carboxyl-, benzyl-, sulfonate-, chloro-, and phosphatoethyl-derivatized alkyls. Essential physicochemical properties including zeta potential, isoelectric point, morphology, surface area, porosity, surface density, and elemental composition of the particles were investigated, followed by biodegradability testing using the Closed Bottle Test (OECD 301D). None of the particles met the biodegradability threshold value of 60%. Only a slight biodegradation was revealed for SiO2-Benzyl (13.7 +/- 6.7%) and for SiO2-3-Chlorpropane (10.8 +/- 1.5%). For the other particles biodegradability was below the normal background fluctuation of 5%. The results were different of those obtained from structurally similar chemicals not being functionalized on the particle surface and from general rules of structure-biodegradation prediction of organic molecules. Therefore, our results suggest that the attachment of the organic groups heavily reduces their biodegradability, increases their residence time and possibility for adverse effects to environmental species. (C) 2013 Elsevier Ltd. All rights reserved
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