Bioactive polymer grafting onto titanium alloy surfaces

Abstract

Bioactive polymers bearing sulfonate (styrene sodium sulfonate, NaSS) and carboxylate (methylacrylic acid, MA) groups were grafted onto Ti6Al4V alloy surfaces by a two-step procedure. The Ti alloy surfaces were first chemically oxidized in a piranha solution and then directly subjected to radical polymerization at 70°C in absence of oxygen. The grafted surfaces were characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the Toluidin blue colorimetric method. Toluidin blue results showed 1 to 5 g/cm 2 of polymer was grafted onto the oxidized Ti surfaces. Grafting resulted in a decrease in the XPS Ti and O signals from the underlying Ti substrate and a corresponding increase in the XPS C and S signals from the polymer layer. The ToF-SIMS intensities of the S − and SO − ions correlated linearly with the XPS atomic percent S concentrations and the ToF-SIMS intensity of the TiO 3 H 2 − ion correlated linearly with the XPS atomic percent Ti concentration. Thus, the ToF-SIMS S − , SO − and TiO 3 H 2 − intensities can be used to quantify composition and amount of grafted polymer. ToF-SIMS also detected ions that were more characteristic of the polymer molecular structure (C 6 H 4 SO 3 − and C 8 H 7 SO 3 − from NaSS, C 4 H 5 O 2 − from MA), but the intensity of these peaks depended on the polymer thickness and composition. An in vitro cell culture test was carried out with human osteoblast-like cells to assess the influence of the grafted polymers on cell response. Cell adhesion after 30 min of incubation showed significant differences between the grafted and un-grafted surfaces. The NaSS grafted surfaces showed the highest degree of cell adhesion while the MA-NaSS grafted surfaces showed the lowest degree of cell adhesion. After 4 weeks in vivo in rabbit femoral bones bone was observed to be in direct contact with all implants. The percent of mineralized tissue around the implants was similar for NaSS grafted and non-grafted implants (59 and 57%). The MA-NaSS grafted implant exhibited a lower amount of mineralized tissue (47%). Keywords

Contributions of adhesive proteins to the cellular and bacterial response to surfaces treated with bioactive polymers: case of poly(sodium styrene sulfonate) grafted titanium surfaces

“…Poly(NaSS) radical grafting was performed under an inert atmosphere (&99 % argon) as described by [20][21][22]. Briefly, Ti6Al4V samples were chemically oxidized by immersion in sulfuric acid/dH 2 O (50/50 v/v, Sigma) for 1 min and then in hydrogen peroxide (Sigma), for 3 min.…”

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates

“…Increased proliferation and adhesion of fibroblasts, 6 MG63 osteoblast-like cells, [7][8][9] and human mandibular osteoblasts 10 have been shown in vitro on sodium styrene sulfonate (NaSS) modified Ti and poly(ethylene terephthalate) surfaces. Promising results have also been obtained in vivo for the same surfaces.…”

“…Two general grafting methods for NaSS surface modification were employed in previous studies on Ti surfaces: (1) surface-initiated radical polymerization from titanium peroxide groups obtained by chemical oxidation of the Ti; 8,9,12 and (2) solution-initiated free-radical polymerization onto 3-methacryloxypropyltrimethoxysilane functionalized Ti. 7,13 While these grafting methods produced films that successfully demonstrated the beneficial effects of grafted NaSS, they do not allow the control of the grafted polymers in terms of chain length uniformity, thickness, etc.…”

Experimental design and analysis of activators regenerated by electron transfer-atom transfer radical polymerization experimental conditions for grafting sodium styrene sulfonate from titanium substrates

“…Interest in NaSS extends to a number of applications, such as an antiflocculating agent, emulsifier, catalyst, and for use in ion-exchange resins and membranes. [18][19][20][21] It has also shown promise as a strategy to increase the osseointegration of titanium [22][23][24][25] and poly(ethylene terephthalate) 26-28 biomedical implants. To investigate possible reasons for the increased osseointegration of these materials, in future studies, the authors intend to test the hypothesis that the NaSS-grafted surfaces preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone.…”