Exploring proteins in Roughland: on the adsorption of proteins on biomaterials for osseointegration

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Wettability of Nanostructured Surfaces

There are many studies in literature concerning contact angle measurements on different materials/substrates. It is documented that textiles can be coated with multifunctional materials in form of thin films or nanoparticles to acquire characteristics that can improve the protection and comfort of the wearer. The capacity of oxide nanostructures to inhibit fungal development and neutralize bacteria is a direct consequence of their wetting behavior [1–6]. Moreover, the radical modification of wetting behavior of nanostructures from hydrophilic to hydrophobic when changing the pulsed laser deposition (PLD) ambient will be thoroughly discussed

The role of nanomaterial-protein interactions in determining the toxic consequences of nanomaterial exposure

As early biological responses to foreign objects in the body can be influenced by their bound proteins, the nanomaterial hard protein corona (the collection of slow exchange proteins that associate with nanomaterials) is an emerging area of interest in nanotoxicology. There is a limited but growing appreciation of the role these interactions have in influencing nanomaterial toxicity. This research dealt with (i) the characterisation of iron oxide and silica particles with and without a plasma, serum and lung lining fluid protein hard corona, (ii) the identification of the proteins in the hard corona that associate with the particles and (iii) the effect of the hard corona on influencing particle cytotoxicity in a J774.A1 macrophage cell line. Initial investigation of the particles illustrates the advantages in using a variety of characterisation techniques to better elucidate particle properties. Subsequent characterisation of the hard corona protein profile demonstrated a clear difference in the biological identity of the particles in a plasma, serum and in a lung lining fluid corona. Although it is difficult to associate the impact of any individual protein identified in the hard corona to cytotoxicity this study indicates that the binding of proteins plays a significant role in altering the cytotoxic potential (as determined by LDH release) in macrophages. The work also demonstrates the hard corona has an impact on macrophage chemotaxis, which further strengthens the hypothesis that the corona is a key consideration in nanoparticle toxicity. Ultimately this thesis finds that the nanomaterial hard corona is an important element to consider in experimental design and highlights the concept of creating particle preparation protocols to mimic the corona composition in vivo when examining in vitro cellular responses. This research highlights the implications for interpretation of data from in vitro cell culture tests that do not take the protein corona into consideration

Development of osteoinductive Si-based coatings to improve dental implants' performance

290 p.Since Professor Brånemark introduced the new concept of osseointegration and the proposal of titanium as the best choice for implants production, many efforts have been done to modify their surface in order to improve the direct bone-implant contact and in this way accelerate osseointegration process.The aim of this thesis work is on the one hand to accelerate the osseointegration process to avoid the appearance of possible problems during the first stages after implantation, and on the other hand, to promote the osteoinductive ability of implants making them widespread and accessible for every type of patients, moreover under unfavourable conditions. With this purpose, bioactive and osteoinductive coatings based on silicon precursors and obtained through the sol-gel process have been developed

Nanostructured sonogels

Acoustic cavitation effects in sol-gel liquid processing permits to obtain nanostructured materials, with size-dependent properties. The so-called "hot spots" produce very high temperatures and pressures which act as nanoreactors. Ultrasounds force the dissolution and the reaction stars. The products (alcohol, water and silanol) help to continue the dissolution, being catalyst content, temperature bath and alkyl group length dependent. Popular choices used in the preparation of silica-based gels are tetramethoxysilane (TMOS), Si(OCH3)4 and tetraethoxysilane (TEOS), Si(OC 2H5)4. The resultant "sonogels" are denser gels with finer and homogeneous porosity than those of classic ones. They have a high surface/volume ratio and are built by small particles (1 nm radius) and a high cross-linked network with low -OH surface coverage radicals. In this way a cluster model is presented based on randomly-packed spheres in several hierarchical levels that represent the real sonoaerogel. Organic modified silicates (ORMOSIL) were obtained by supercritical drying in ethanol of the corresponding alcogel producing a hybrid organic/inorganic aerogel. The new material takes the advantages of the organic polymers as flexibility, low density, toughness and formability whereas the inorganic part contributes with surface hardness, modulus strength, transparency and high refractive index. The sonocatalytic method has proven to be adequate to prepare silica matrices for fine and uniform dispersion of CdS and PbS quantum dots (QDs), which show exciton quantum confinement. We present results of characterization of these materials, such as nitrogen physisorption, small angle X-ray/neutrons scattering, electron microscopy, uniaxial compression and nanoindentation. Finally these materials find application as biomaterials for tissue engineering and for CO2 sequestration by means the carbonation reaction.Ministerio de Ciencia y Tecnología MAT2005-158

The effects of high power diode laser radiation on the wettability, adhesion and bonding characteristics of an alumina/silica-based oxide and vitreous enamel

An amalgamated alumina/silica-based oxide compound (AOC) was surface treated using a 60 W high power diode laser (HPDL). The effects of HPDL radiation on the wettability and adhesion characteristics of the AOC and a vitreous enamel have been determined. The basic process phenomena are investigated and the effects of laser irradiation in terms of composition and microstructure are presented. Without laser treatment of the AOC surface it was not possible to fire the enamel onto the AOC. However, wetting experiments using a number of control liquids, by the sessile drop technique, revealed that laser treatment of the AOC surface resulted in the polar component of the surface energy increasing after laser treatment from 2.00 mJm-2 to 16.15 mJm-2. Additionally, surface roughness measurements revealed that after laser treatment, the surface roughness had decreased from an Ra value of 25.85μm to 6.27μm, whilst an energy disperse X-ray analysis (EDX) revealed that the relative surface oxygen content of the AOC had increased by 36.29% after laser treatment. Thus, laser treatment was identified as effecting a decrease in the enamel contact angle from 1180 to 330; consequently allowing the vitreous enamel to wet the surface. The bonding mechanisms were identified as being principally due to van der Waals forces, however, some evidence of chemical bonding was observed. The work has shown clearly that laser radiation can be used to alter the wetting characteristics of the AOC

The immune system dependency of the protein corona

Biomedical applications of nanocarriers are a research field with increasing focus within the scientific community. Through the blood stream, nanocarriers may transport drugs or reporter molecules to specific cells or tissues without exposing them to other parts of the organism. Upon interactions of nanocarriers with blood proteins, a protein corona is formed. These interactions with proteins tremendously influence the properties and behavior of nanocarriers in biological media. In order to achieve applicable nanomedicines, control over the protein corona is required. The blood composition of individuals varies vastly based on constitution, environmental conditions and nutrition. Immunoglobulins are a protein class that is particularly affected by the individual state of the immune system. Therefore, the aim of this work is to investigate the interactions nanocarriers undergo with different immunoglobulins and how varrying immunoglobulin concentrations in blood plasma affect the protein corona. First, the interactions, which differently charged polymeric nanoparticles undergo with different immunoglobulins in the form of IgG, IgA, and IgM were investigated. Each immunoglobulin class showed different binding parameters to the different nanoparticles and in some cases induced aggregation processes. All immunoglobulins appeared denatured on the surface of nanoparticles with the possible consequence of unwanted reactions of the immune system. Afterwards, the protein corona of different nanocarriers was compared after incubation in pooled blood plasma and blood plasma of varied, physiologically relevant immunoglobulin concentrations. For this, averaged plasma was modified by increasing IgG, IgA, or IgM or by decreasing the IgG concentration. In all four cases, a significant alteration of the protein corona was observed. The promoted adsorption of IgG in IgG-enriched plasma was further analyzed and resulted in a promoted uptake in macrophages. The effects of IgG-enriched plasma on the protein corona could be prevented successfully by pre-incubation of nanocarriers with the protein clusterin. Finally, poly(ethylene glycol)-binding IgG was quantified in blood plasma and the protein corona of different nanocarriers. It could be observed, that the concentration of these antibodies was relatively high on nanocarriers containing poly(ethylene glycol)-chains on their surface. In conclusion, further understanding of the complex interactions nanocarriers undergo with blood proteins with special regards to immunoglobulins was gained. By pre-incubation with clusterin, nanocarriers behave more independent on the individual blood composition.154 Seite