Protein selective adsorption properties of a polyethylene terephtalate artificial ligament grafted with poly(sodium styrene sulfonate) (polyNaSS): correlation with physicochemical parameters of proteins.

Immediately after surgical placement of biomaterials, a first step consists in the adsorption of proteins from the biological environment on the artificial surfaces. Because the composition of the adsorbed protein layer modulates the cell response to the implanted material, researchers in the biomaterials field have focused on coating proteins or peptides onto surfaces to improve cell response and therefore the long-term compatibility of the implant. However, some materials used in tissue engineering, mainly synthetic polymers, are too hydrophobic to allow the optimal adsorption of proteins and have to be first submitted to physical or chemical treatments. In our laboratory, we have demonstrated that grafting of poly(sodium styrene sulfonate) (polyNaSS) onto biomaterials can strongly modulate the protein adsorption and the cellular response compared to unmodified surfaces. In this study, we used a liquid chromatography strategy coupled to proteomics to evaluate the adsorptive properties of a polyethylene terephtalate (PET) artificial ligament grafted with polyNaSS, and to identify and analyse proteins adsorbed on PET fibers. Results obtained with platelet rich plasma (PRP) proteins demonstrated that grafting significantly increases the protein adsorption of the PET and also selectively modulates the adsorption of proteins on PET fibers. Finally, regarding physicochemical parameters calculated from the amino acid sequence of identified proteins, we found that the aliphatic index is highly correlated with the selective adsorption of proteins onto the polyNaSS/PET surface. Therefore, the proteomic approach complemented with physicochemical property evaluation could provide a powerful tool for the elaboration of new biomaterials based on protein layer deposition.

Biotribocorrosion (tribo-electrochemical) characterization of anodized titanium biomaterial containing calcium and phosphorus before and after osteoblastic cell culture.

The purpose of this study was to investigate the relationship between the osteoblastic cells behavior and biotribocorrosion phenomena on bioactive titanium (Ti). Ti substrates submitted to bioactive anodic oxidation and etching treatments were cultured up to 28 days with MG63 osteoblast-like cells. Important parameters of in vitro bone-like tissue formation were assessed. Although no major differences were observed between the surfaces topography (both rough) and wettability (both hydrophobic), a significant increase in cell attachment and differentiation was detected on the anodized substrates as product of favorable surface morphology and chemical composition. Alkaline phosphatase production has increased (≈20 nmol/min/mg of protein) on the anodized materials, while phosphate concentration has reached the double of the etched material and calcium production increased (over 20 µg/mL). The mechanical and biological stability of the anodic surfaces were also put to test through biotribocorrosion sliding solicitations, putting in evidence the resistance of the anodic layer and the cells capacity of regeneration after implant degradation. The Ti osteointegration abilities were also confirmed by the development of strong cell-biomaterial bonds at the interface, on both substrates. By combining the biological and mechanical results, the anodized Ti can be considered a viable option for dentistry.

The osteogenic differentiation improvement of human mesenchymal stem cells on titanium grafted with polyNaSS bioactive polymer.

Osseointegration of metallic implants used in orthopedic surgery requires that osteoprogenitor cells attach and adhere to the surface, then proliferate, differentiate into osteoblasts, and finally produce mineralized matrix. Because the ability of progenitor cells to attach to a scaffold surface during early stages is important in the development of new tissue structures, we developed in our laboratory, a strategy involving grafting of implants with a polymer of sodium styrene sulfonate (polyNaSS) used as a scaffold which enables human mesenchymal stem cells (hMSCs) interactions. In the present study, we investigated the cellular response of hMSCs to polyNaSS surfaces of titanium (Ti). In particular, cell proliferation, cell viability, cell differentiation, and cell spreading were evaluated. Results showed that cell proliferation and cell viability did not differ with any statistical significance between modified and unmodified Ti surfaces. Interestingly, culture of MSCs on polyNaSS surfaces resulted in a significant increase of cell spreading and cell differentiation compared with the other tested surfaces. These results suggest that titanium surface grafted with polyNaSS is a suitable scaffold for bone tissue engineering.

Development of proteomic tools to study protein adsorption on a biomaterial, titanium grafted with poly(sodium styrene sulfonate).

It is known that protein adsorption is the initial interaction between implanted biomaterials and biological environment. Generally, a complex protein layer will be formed on material surfaces within a few minutes and the composition of this layer at the interface determines the biological response to the implanted material, and therefore the long-term compatibility of the biomaterial. Despite different techniques exist to observe protein adsorption on biomaterials, none of them led to the identification of adsorbed proteins. In this paper, we report a chromatographic technique coupled to proteomics to analyse and identify proteins from complex biological samples adsorbed on biomaterial surfaces. This approach is based on (1) elaboration of the chromatographic support containing the biomaterial (2) a chromatography step involving adsorption of proteins on the biomaterial (3) the high-resolution separation of eluted proteins by 2-DE gel and (4) the identification of proteins by mass spectrometry. Experiments were performed with proteins from platelets rich plasma (PRP) adsorbed on a biomaterial which consist in titanium bioactivated with PolyNaSS. Our results show that chromatographic approach combined to 2-DE gels and mass spectrometry provides a powerful tool for the analysis and identification of proteins adsorbed on various surfaces.