Géraldine Rohman

Preliminary In Vitro Assessment of Stem Cell Compatibility with Cross-Linked Poly(ε-caprolactone urethane) Scaffolds Designed through High Internal Phase Emulsions

By using a high internal phase emulsion process, elastomeric poly(ε-caprolactone urethane) (PCLU) scaffolds were designed with pores size ranging from below 150 μm to 1800 μm and a porosity of 86% making them suitable for bone tissue engineering applications. Moreover, the pores appeared to be excellently interconnected, promoting cellularization and future bone ingrowth. This study evaluated the in vitro cytotoxicity of the PCLU scaffolds towards human mesenchymal stem cells (hMSCs) through the evaluation of cell viability and metabolic activity during extract test and indirect contact test at the beginning of the scaffold lifetime. Both tests demonstrated that PCLU scaffolds did not induce any cytotoxic response. Finally, direct interaction of hMSCs and PCLU scaffolds showed that PCLU scaffolds were suitable for supporting the hMSCs adhesion and that the cells were well spread over the pore walls. We conclude that PCLU scaffolds may be a good candidate for bone tissue regeneration applications using hMSCs.

Characterization of a synthetic bioactive polymer by nonlinear optical microscopy

Tissue Engineering is a new emerging field that offers many possibilities to produce three-dimensional and functional tissues like ligaments or scaffolds. The biocompatibility of these materials is crucial in tissue engineering, since they should be integrated in situ and should induce a good cell adhesion and proliferation. One of the most promising materials used for tissue engineering are polyesters such as Poly-ε-caprolactone (PCL), which is used in this work. In our case, the bio-integration is reached by grafting a bioactive polymer (pNaSS) on a PCL surface. Using nonlinear microscopy, PCL structure is visualized by SHG and proteins and cells by two-photon excitation autofluorescence generation. A comparative study between grafted and nongrafted polymer films is provided. We demonstrate that the polymer grafting improves the protein adsorption by a factor of 75% and increase the cell spreading onto the polymer surface. Since the spreading is directly related to cell adhesion and proliferation, we demonstrate that the pNaSS grafting promotes PCL biocompatibility.

The grafting of a thin layer of poly(sodium styrene sulfonate) onto poly(ε-caprolactone) surface can enhance fibroblast behavior

Poly(sodium styrene sulfonate) (pNaSS) was grafted onto poly(ε-caprolatone) (PCL) surfaces via ozonation and graft polymerization. The effect of ozonation and polymerization time, as well as the Mohr’s salt concentration in the grafting solution, on the degree of grafting was investigated. The degree of grafting was determined through toluidine blue staining. The surface chemical change was characterized by attenuated total reflection Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The result demonstrated that the grafting did not induce any degradation of PCL, and that pNaSS was grafted onto PCL as a thin and covalently stable layer. Furthermore, the modified PCL surface reveals a significant increase in the metabolic activity of fibroblastic cells, as well as a better cell spreading with higher adhesion strength. Consequently, bioactivity of PCL is greatly enhanced by immobilizing a thin layer of pNaSS onto its surface. The grafting of pNaSS is a promising approach to increase the bioactivity of PCL-based materials used in tissue engineering applications, such as ligament reconstruction.

Improved proliferation and osteogenic differentiation of human mesenchymal stem cells on a titanium biomaterial grafted with poly(sodium styrene sulphonate) and coated with a platelet-rich plasma proteins biofilm

In order to replace damaged or lost bone in the human body, it is necessary to produce ‘spare body parts’ which are dependent on the use of biomaterial and stem cells and are referred to as ‘tissue engineering’. Surface modification and stem cell interaction of orthopaedic implants offer a promising approach and are investigated here specifically to improve osseointegration of the biomaterial. Osseointegration of titanium implants used in orthopaedic surgery requires that osseo-progenitor cells attach and adhere to the surface, proliferate, then differentiate into osteoblasts and, finally, produce a mineralised matrix. The surface modification of titanium with anionic polymer combined with coating of platelet-rich plasma is provided to create a favourable environment to promote early and strong fixation of implants. The ability of progenitor cells to attach to the surface during early stages is important in the development of new tissue structures; therefore, we developed in our laboratory a strategy involving the grafting of titanium implants with a polymer of sodium styrene sulphonate (poly(sodium styrene sulphonate)) and a biofilm coating of platelet-rich plasma which enables human mesenchymal stem cell interactions. The resulting biomaterial, titanium-poly(sodium styrene sulphonate) and coating of platelet-rich plasma, Ti-poly(sodium styrene sulphonate)–platelet-rich plasma was developed in order to further improve the biomaterial. In this work, we studied and characterised the ‘in vitro’ response of human mesenchymal stem cells to titanium biomaterial grafted with poly(sodium styrene sulphonate) bioactive polymer and coated with platelet-rich plasma proteins (Ti-poly(sodium styrene sulphonate)–platelet-rich plasma). This study shows an increased cell proliferation with Ti-poly(sodium styrene sulphonate)–platelet-rich plasma compared to foetal calf serum and an enhancement of the Ti-poly(sodium styrene sulphonate)–platelet-rich plasma effects on osteoblast differentiation. The results suggest that Ti-poly(sodium styrene sulphonate)–platelet-rich plasma would be a suitable scaffold for bone tissue engineering.