David Portet

Self-Assembled Monolayers of Bisphosphonates: Influence of Side Chain Steric Hindrance

Bisphosphonates form self-assembled monolayers (SAMs) spontaneously on stainless steel, silicon, and titanium oxidized surfaces. We used contact angle measurements, atomic force microscopy, and X-ray reflectivity analysis to study the formation of SAMs on a model surface of ultraflat titanium (rms = 0.2 nm). The results were extended to standard materials (mechanically polished titanium, stainless steel, and silicon) and showed that water-soluble bisphosphonic perfluoropolyether can easily form SAMs, with 100% surface coverage and a layer thickness of less than 3 nm. Hydrophobic (water contact angle >110 degrees on stainless steel or titanium) and lipophobic (methylene iodide contact angle >105 degrees on titanium) properties are discussed in terms of industrial applications.

In vitro kinetic study of growth and mineralization of osteoblast‐like cells (Saos‐2) on titanium surface coated with a RGD functionalized bisphosphonate

Osteoconduction and osseointegration are the critical stages for implantation success. Peptides containing RGD (Arg-Gly-Asp) adhesive sequence are known to promote cell adhesion and consequently to favor osseointegration of medical devices. In this study, RGD peptides were coupled to a bisphosphonate used as an anchor system and chemically adsorbed on polished titanium discs. Two different concentrations, 10(-10) mol/L (RGD 10(-10)) and 10(-4) mol/L (RGD 10(-4)) were compared to non coated discs (RGD 0). Adhesion, spreading, and mineralization of osteoblast-like cells (Saos-2) were assessed. Mineralization kinetic was done at 3, 6, 10, 14, and 18 days of culture; the extent of mineral deposits was quantified by image analysis. Histogram repartitions of nuclear area, characterizing cell spreading, showed a shift to higher values in cells cultured on RGD coated titanium disks. Mineralization started at day 3 in the three groups, but had a faster development in the RGD 10(-10) group from day 6 to day 18 compared to RGD 0 and RGD 10(-4). At day 18, the percentage of mineralized area was significantly higher for RGD 10(-10) compared to RGD 0 (p < 0.05). In the present study, this new method was found suitable to anchor RGD containing species on titanium: this favored adhesion and spreading of osteoblast-like cells and mineralization compared to noncoated titanium.