No abstract

The anchorage failure of titanium implants in human body is mainly due to biointegration problem. The proposed solution is to graft a bioactive polymer at the surface of the implant in order to improve and control the interactions with the living system. In this paper, we describe the grafting of poly sodium styrene sulfonate on titanium surface by using a silanization reaction. The key point is to increase the TiOH content at the surface of the implant which can react with methoxy silane groups of 3-methacryloxypropyltrimethoxysilane (MPS). Two procedures were used: chemical oxidation and electrochemical oxidation. The last oxidation procedure was carried out in two different electrolytes: oxalic acid and methanol. These different oxidation methods allow controlling the roughness and the depth of the oxide layer. The methacryloyl group of MPS grafted at the titanium surface by silanization reaction is copolymerized with sodium styrene sulfonate using a thermal initiator able to produce radicals by heating. Colorimetric method, ATR-FTIR, XPS techniques and contact angle measurements were applied to characterize the surfaces. MG63 osteoblastic cell response was studied on polished, oxidized and grafted titanium samples. Cell adhesion, Alkaline Phosphatase activity and calcium nodules formation were significantly enhanced on grafted titanium surfaces compared to un-modified surfaces.

Full-scale cell penetration within porous scaffolds is required to obtain functional connective tissue components in tissue engineering applications. For this aim, we produced porous polyurethane structures with well-controlled pore and interconnection sizes. Although the influence of the pore size on cellular behavior is widely studied, we focused on the impact of the size of the interconnections on the colonization by NIH 3T3 fibroblasts and Wharton's jelly-derived mesenchymal stem cells (WJMSCs). To render the material hydrophilic and allow good material wettability, we treated the material either by plasma or by polydopamine (PDA) coating. We show that cells weakly adhere on these surfaces. Keeping the average pore diameter constant at 133 μm, we compare two structures, one with LARGE (52 μm) and one with SMALL (27 μm) interconnection diameters. DNA quantification and extracellular matrix (ECM) production reveal that larger interconnections is more suitable for cells to move across the scaffold and form a three-dimensional cellular network. We argue that LARGE interconnections favor cell communication between different pores, which then favors the production of the ECM. Moreover, PDA treatment shows a truly beneficial effect on fibroblast viability and on matrix production, whereas plasma treatment shows the same effect for WJMSCs. We, therefore, claim that both pore interconnection size and surface treatment play a significant role to improve the quality of integration of tissue engineering scaffolds.

Creating substrates with a similar composition that can either prevent or promote cell adhesion is still a challenging feat. Here, it is shown that a strikingly simple method of tuning the amount of hard segments or isocyanate index (NCOind) of a polyurethane (PU) film allows to modulate cell adhesiveness. PU films are synthesized with NCOind of 75, 100, 200, 300 and 400 corresponding to ratios of isocyanate to hydroxyl functions of 0.75, 1, 2, 3, 4, respectively. The adhesive capacity of NIH 3T3 fibroblasts (3T3) and Wharton's jelly mesenchymal stem cells (WJMSCs) are dependent on the NCOind. For NCOind below 300, no cell adhesion can be observed regardless of the cell type, whereas for NCOind of 300 and 400 cells adhere to the PU surface. WAXS and small angle X‐ray scattering (SAXS) studies reveal that variations of NCOind allows to modulate the phase separation in PU films. Porod's law shows that for NCOind of 300 and 400, the hard–soft segment interface is sharp. Conversely, samples with smaller NCOind present diffuse interfaces. Hence, the morphology of the interface between hard and soft domains appears to be a critical feature that correlates with the adhesion capacity of cells.