RESUMEN
Gradients in surface nanotopography were prepared by adsorbing gold nanoparticles on smooth gold substrates using diffusion technique. Following a sintering procedure the particle binding chemistry was removed, and integration of the particles into the underlying gold substrate was achieved, leaving a nanostructured surface with uniform surface chemistry. After pre-adsorption of human fibrinogen, the effect of surface nanotopography on platelets was studied. The use of a gradient in nanotopography allowed for platelet adhesion and activation to be studied as a function of nanoparticle coverage on one single substrate. A peak in platelet adhesion was found at 23% nanoparticle surface coverage. The highest number of activated platelets was found on the smooth control part of the surface, and did not coincide with the number of adhered platelets. Activation correlated inversely with particle coverage, hence the lowest fraction of activated platelets was found at high particle coverage. Hydrophobization of the gradient surface lowered the total number of adhering cells, but not the ratio of activated cells. Little or no effect was seen on gradients with 36nm particles, suggesting the existence of a lower limit for sensing of surface nano-roughness in platelets. These results demonstrate that parameters such as ratio between size and inter-particle distance can be more relevant for cell response than wettability on nanostructured surfaces. The minor effect of hydrophobicity, the generally reduced activation on nanostructured surfaces and the presence of a cut-off in activation of human platelets as a function of nanoparticle size could have implications for the design of future blood-contacting biomaterials.
Asunto(s)
Nanotecnología , Adsorción , Difusión , Fibrinógeno/química , Oro/química , Humanos , Nanopartículas del Metal/química , Tamaño de la Partícula , Activación Plaquetaria , Adhesividad Plaquetaria , Valores de Referencia , Propiedades de SuperficieRESUMEN
Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to study the viscoelastic properties of the blue mussel, Mytilus edulis, foot protein 1 (Mefp-1) adsorbed on modified hydrophobic gold surfaces. The change in viscoelasticity was studied after addition of Cu2+ and Mn2+, which theoretically could induce metal complex formation with 3,4-dihydroxyphenylalanine (DOPA) moieties. We also used NaIO4, a nonmetal oxidative agent known to induce di-DOPA formation. Reduction in viscoelasticity of adsorbed Mefp-1 followed the order of NaIO4 > Cu2+ > buffer control > Mn2+. We also studied the formation of molecular aggregates of Mefp-1 in solution with the use of dynamic light scattering (DLS). We found that addition of Cu2+, but not Mn2+, induced the formation of larger DLS-detectable aggregates. Minor aggregate formation was found with NaIO4. With the analytical resolution of small angle X-ray scattering (SAXS), we could detect differences in the molecular structure between NaIO4- and Cu2+-treated Mefp-1 aggregates. We concluded from this study that Cu2+ could participate in intermolecular cross-linking of the Mefp-1 molecule via metal complex formation. Metal incorporation in the protein most likely increases the abrasion resistance of the Mefp-1 layer. NaIO4, on the other hand, resulted in mainly intramolecular formation of di-DOPA, but failed to induce larger intermolecular aggregation phenomena. The described methodological combination of surface sensitive methods, like QCM-D, and bulk sensitive methods, like DLS and SAXS, generates high resolution results and is an attractive platform to investigate intra- and intermolecular aspects of assembly and cross-linking of the Mefp proteins.
Asunto(s)
Cobre/farmacología , Mitógenos/farmacología , Mytilus edulis/química , Ácido Peryódico/farmacología , Proteínas/química , Proteínas/metabolismo , Animales , Cloruros/farmacología , Reactivos de Enlaces Cruzados/farmacología , Dihidroxifenilalanina/química , Oro Coloide/química , Compuestos de Manganeso/farmacología , Oxidación-Reducción , Unión Proteica , Propiedades de Superficie , Viscosidad , Rayos XRESUMEN
Although numerous different polymers are used as implants or otherwise studied for many other biotechnical applications, there is a lack of basic models that correlate polymer characteristics with foreign body reactions. This study aims at developing one such model by systematically studying surface molecular mobility of polymeric implants in soft tissues in vivo. Changing the length of the alkyl side chain of poly(alkyl methacrylates) (PAMAs), provides an interesting opportunity to study the surface molecular mobility with minimal changes of the hydrophobicity of the surface. Thus, in this study three different PAMAs, with increasingly surface mobility; poly (isobutyl methacrylate) (PIBMA), poly(butyl methacrylate) (PBMA), and poly(lauryl methacralate) (PLMA) along with pure titanium (Ti) substrates were implanted in the dorsum of Sprague-Dawley rats. Inflammatory cell recruitment, cell adhesion, and cytokine release were studied after 1, 3, and 28 days of implantation. Total number of inflammatory cells in the exudate was measured but no correlation between surface mobility and cell recruitment where found. However, the number of surface associated cells where significantly lower on the surfaces with high molecular mobility (PLMA and PBMA). The histological evaluation performed after 28 days revealed thicker fibrous capsule and a higher number of blood vessels on the low molecular mobility surface (PIBMA). After 28 days the cell activity was higher on the high molecular mobility surfaces (PLMA and PBMA) compared with PIBMA, based on the cytokine release. None of the surfaces induced any significant cell-death. On the basis of the results of this study we conclude that there is a significant difference in biological response to surfaces with different in molecular mobility. This might affect the wound healing process and the biocompatibility of biomaterials.
Asunto(s)
Materiales Biocompatibles , Polímeros , Prótesis e Implantes , Tejido Subcutáneo/patología , Animales , Materiales Biocompatibles/química , Materiales Biocompatibles/metabolismo , Modelos Biológicos , Polímeros/química , Polímeros/metabolismo , Ácidos Polimetacrílicos/química , Ácidos Polimetacrílicos/metabolismo , Ratas , Ratas Sprague-Dawley , TitanioRESUMEN
An overlooked factor in biomaterial research is the surface molecular flexibility for polymer based implants. The mobility of the polymer chains provides a way for the surface to adapt itself to the environment. This is relevant when the implant comes in contact with a biological fluid and its constituents. By changing the length of the alkyl side chain of poly(alkyl methacrylates) (PAMAs) an interesting opportunity is provided where it is possible to study the surface molecular mobility without changing the surface hydrophobicity, nor does it introduce any additives or any changes in the degree of polymer cross-linking. Four variants of PAMAs were implanted in the peritoneum of Balb/c mice using a well described setup. End points were taken after 18 h and estimations of inflammatory cell recruitment and implant-associated cells were studied. Relationship between surface molecular mobility and inflammatory cell recruitment as well as surface-associated cells was noted.