Among plant derived molecules, polyphenols have antioxidant, anticancer and antibacterial ability [1,2]. Moreover, they can stimulate osteoblast differentiation and promote apoptosis of tumoral cells [3–4]. It's thus possible combine the properties of these molecules with those of bioactive materials trough surface functionalization. A silica-based bioactive glass and chemically treated bioactive Ti6Al4V were used as substrates while gallic acid and polyphenols extracted from green tea or red grape skin as biomolecules for functionalization. The surface functionalization procedure was optimized in order to maximize the grafting and investigated by means of the Folin&Ciocalteu method and X-Ray Photoelectron Spectroscopy (XPS) analyses. The Surface charge and isoelectric point were investigated by means of zeta potential measurements. Free radical scavenging activity evaluation was performed in order to investigate the antioxidant ability of glass samples. Finally, the functionalization selective killing activity towards osteosarcoma cells was The presence of polyphenols on the surfaces was confirmed by XPS analyses by the appearance of characteristic peaks (C-O and C=O bonds) in the carbon and oxygen regions. The Folin&Ciocalteu test demonstrated the presence and activity of polyphenols on all the substrates and evidenced a clear relation between surface reactivity and grafting ability. The bioactivity tests showed the deposition of hydroxyapatite on the functionalized samples and an influence of biomolecules on its amount and shape for glasses. Zeta potential measurements evidenced a shift of the isoelectric point of glass samples after functionalization. A certain antioxidant activity of bare glass has been evidenced and it is improved by the grafting of tea polyphenols. Accordingly, MTT results confirmed polyphenols selective killer activity towards osteosarcoma cells whose viability was significantly decreased in comparison with safe bone cells. XPS analyses, zeta potential measurements and Folin&Ciocalteu tests showed the presence and the activity of the polyphenols on the surfaces. Bioactivity tests highlighted an improvement of the deposition of hydroxyapatite on the surface of the functionalized glass samples. Certain antioxidant ability has been evidenced for glass samples and was further improved by tea polyphenols. Moreover, a selective toxic activity towards tumor cells was In conclusions polyphenols were successfully grafted to the surface of glass and Ti6Al4V samples maintaining their activity. Polyphenols improve in vitro bioactivity, antioxidant and anticancer ability of glass. The surface functionalization seems to be a good way to combine the properties of bioactive materials for bone contact applications with those of polyphenols.
The problem facing this research is to promote rapid osteointegration of titanium implants and to minimise the risks of infections by the functionalization with different agents, each designed for a specific action. A patented process gives a multifunctional titanium surface. A patented process of surface modification is described. It gives a multifunctional surface with a multiscale roughness (micro and nano topography), that is excellent for osteoblast adhesion and differentiation. It has a high degree of hydroxylation, that is relevant for inorganic bioactivity (apatite-HA precipitation) and it is ready for a functionalization with biological factors. A direct grafting of ALP has been obtained. Moreover, the growth of an antibacterial agent within the surface oxide layer can be useful in order to combine the osteoinduction ability to antimicrobial effects. The selection of an inorganic agent (metal nanoparticles) has the advantage to avoid an eventual development of antibiotic resistance by bacteria.Summary Statement
Introduction
