Hydrolysestabile Bioaktivierung medizinischer Hochleistungskeramik durch Quervernetzung von RGD-Peptiden, BMP-2- und HGF-Proteinen an Silan-Monoschichten

The aim of the present work was the development and characterization of a hydrolytically stable biological activation of the high performance ceramics Al2O3, Y-TZP, ZTA, and ATZ via crosslinking of c(RGDyK), BMP-2 and HGF. The Hypothesis was the significant promotion of adhesion and osteogenic differentiation of hMSC by the biological activation. For this, hydrolytically stable adhesion promoting SiOx-films were deposited by the comparison of two methods, PVD and PE-CVD. The adhesive strength of the films was proven via tensile and shear strength tests. Functional groups were introduced by the silanization with APDS, MPTES and THPS as shown by XPS. These served as binding points for the crosslinking with BS3 and SMCC. Successful crosslinking of c(RGDyK) was possible by labeling the Peptide with I125 beforehand. A significant increase in hMSC adhesion was afterwards measured in centrifugation tests up to 50 g. Both HGF and BMP-2 were homogeneously immobilized on the surface, the latter with 323 ng/cm2 and 70 % retention over 21 days after an initial burst release. HGF was additionally genetically modified to express a tPA cleavage site and a Cystein-Linker and successfully coupled to the surface. Cultivation of hMSC on BMP-2 modified surfaces showed their osteogenic differentiation towards osteoblasts. The developed method may enable the tissue integration of a new class of biomaterials in vivo via recruitment and differentiation of endogenous stem cells

Biological Activation of Inert Ceramics: Recent Advances Using Tailored Self-Assembled Monolayers on Implant Ceramic Surfaces

High-strength ceramics as materials for medical implants have a long, research-intensive history. Yet, especially on applications where the ceramic components are in direct contact with the surrounding tissue, an unresolved issue is its inherent property of biological inertness. To combat this, several strategies have been investigated over the last couple of years. One promising approach investigates the technique of Self-Assembled Monolayers (SAM) and subsequent chemical functionalization to create a biologically active tissue-facing surface layer. Implementation of this would have a beneficial impact on several fields in modern implant medicine such as hip and knee arthroplasty, dental applications and related fields. This review aims to give a summarizing overview of the latest advances in this recently emerging field, along with thorough introductions of the underlying mechanism of SAMs and surface cell attachment mechanics on the cell side

Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) yields better Hydrolytical Stability of Biocompatible SiOx Thin Films on Implant Alumina Ceramics compared to Rapid Thermal Evaporation Physical Vapor Deposition (PVD)

Densely sintered aluminum oxide (α-Al₂O₃) is chemically and biologically inert. To improve the interaction with biomolecules and cells, its surface has to be modified prior to use in biomedical applications. In this study, we compared two deposition techniques for adhesion promoting SiO_<i>x</i> films to facilitate the coupling of stable organosilane monolayers on monolithic α-alumina; physical vapor deposition (PVD) by thermal evaporation and plasma enhanced chemical vapor deposition (PE-CVD). We also investigated the influence of etching on the formation of silanol surface groups using hydrogen peroxide and sulfuric acid solutions. The film characteristics, that is, surface morphology and surface chemistry, as well as the film stability and its adhesion properties under accelerated aging conditions were characterized by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductively coupled plasma–optical emission spectroscopy (ICP-OES), and tensile strength tests. Differences in surface functionalization were investigated via two model organosilanes as well as the cell-cytotoxicity and viability on murine fibroblasts and human mesenchymal stromal cells (hMSC). We found that both SiO_<i>x</i> interfaces did not affect the cell viability of both cell types. No significant differences between both films with regard to their interfacial tensile strength were detected, although failure mode analyses revealed a higher interfacial stability of the PE-CVD films compared to the PVD films. Twenty-eight day exposure to simulated body fluid (SBF) at 37 °C revealed a partial delamination of the thermally deposited PVD films whereas the PE-CVD films stayed largely intact. SiO_<i>x</i> layers deposited by both PVD and PE-CVD may thus serve as viable adhesion-promoters for subsequent organosilane coupling agent binding to α-alumina. However, PE-CVD appears to be favorable for long-term direct film exposure to aqueous solutions