Search

International audience; Bone is composed of two phases. The organic phase is made of collagen fibrils assembled in broad fibers acting as a template for mineralization. The mineral phase comprises hydroxyapatite (HAP) crystals grown between and inside the collagen fibers. We have developed a biomimetic material using functionalized carbon nanotubes as scaffold to initiate in vitro mineralization. Biomimetic formation of HAP was performed on single-walled carbon nanotubes (SWCNTs) which have been grafted with carboxylic groups. Two types of nanotubes, HiPco(R) and Carbon Solutions(R), were oxidized via various acidic processes, leading to five different groups of carboxylated nanotubes, fully characterized by physical methods (thermogravimetric analysis, attenuated total reflectance infrared spectroscopy and X-ray photoelectron spectroscopy). All samples were dispersed in ultra-pure water and incubated for 2weeks in a synthetic body fluid, in order to induce the calcification of the SWCNTs. Scanning electron microscopy (SEM) and energy-dispersive X-ray analysis studies showed that Ca(2+) and PO(4)(3-) ions were deposited as round-shaped nodules (calcospherites) on the carboxylated SWCNTs. Fourier transform infrared and Raman spectroscopic studies confirmed the HAP formation, and image analysis made on SEM pictures showed that calcospherites and carboxylated SWCNTs were packed together. The size of calcospherites thus obtained in vitro from the HiPco(R) series was close to that issued from calcospherites observed in vivo. Functionalization of SWCNTs with carboxylic groups confers the capacity to induce calcification similar to woven bone.

International audience; 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.