Grafting of bioactivepolymers onto titanium surfaces and human osteoblasts response
Titanium (Ti) and its alloys are exceptional materials for use in fields such as dentistry due to their resistant to corrosion and its biocompatibility. Though the uses of titanium-based surfaces have been shown to have short term success, problems arise in long run use due to weak integration of implant into the bone tissue. In addition, both specific and non-specific binding of cells and proteins in vivo were reported. In this communication, a titanium surface is chemically modified in order to enhance the absorption of specific proteins and cells. The titanium surface was functionalized with anionic groups by grafting bioactive polymers such as sodium sulfonate. Functionalization was achieved in two steps: surface oxidation with hydrogen peroxide followed by radical polymerization by treatment of sodium styrene sulfonate (NaSS). Human osteoblast-like cells (cell line MG63) were tested for cell adhesion on the modified surface and subsequent mineralization.
A series of analytical techniques were used in order to verify the presence of these anionic groups on the titanium surface: ATR/FTIR allowed for the detection of functional groups; XPS was used for analyzing chemical composition; and profilometry characterized the surface composition. In addition, a colorimetric assay was used to quantify the concentration of functional groups present on the surface. Controls for this experiment included a pure and oxidized titanium surface. MG63 cells were allowed to adhere for 30 minutes and were stirred for 15 minutes thereafter to remove weakly adhered cells.
ATR/FTIR and XPS verified the presence of the functional group on the grafted surface. Profilometry showed that the initial oxidation step resulted in a rough surface while the subsequent step lead to a smoother surface. The functional group was highly concentrated on the grafted surface based on the results of colorimetric assay. The graph showed a statistically significant amount of MG63 cells being adhered to the grafted titanium when compared to both the pure titanium and oxidized titanium surfaces (Fig. 4). However, though the mean amount of mineralization is higher in the grafted titanium case when compared to other two controls, it is difficult to conclude whether these results were statistically significant due to the overlapping error bars (Fig. 5).
Synthetic chemistry allows for grafting of bioactive polymers onto metal surfaces, such as titanium, that can introduce a huge array of functionalities. Though there are huge constraints, such as having bioorthogonal functional groups, that limits the general scope of this technique, various modifications can allow for several other applications beside mineralization.
4 comments:
Here's the link to the article: http://ieeexplore.ieee.org/iel5/4352184/4352185/04353492.pdf?tp=&arnumber=4353492&isnumber=4352185
Hi Panda: I was real excited to read about this paper 'cause of titanium's potential use in the field of dentistry. (yay! you could imagine how ecstatic I got when your very first sentence mentioned the word: dentistry, :^) It is interesting to find out that grafting of bioactive polymers onto metal surfaces allowed for the cell adhesion which then followed by the mineralization. I wonder whether this specific cell adhesion to the modified surface caused any difference in providing the nucleating surface for the subsequent mineralization though? Whether the kinetics of nucleation was altered by the modification or cells adhere homogeneously or heterogenously throughout the modified surface and whether that has any effect on subsequent mineralization? Do you also happen to know whether they have utilized synthetic chemistry to graft bioactive polymers onto any other metal surfaces? Also, you mentioned that the significance of mineralization amount between grafted titanium vs other controls are questionable due to the presence of overlapping error bars in this study. If there was, indeed, a significant difference in the overall mineralization in the presence of modified surface, that'd be a very exciting baby-step towards discovering mechanisms which engineers can utilize to manipulate the kinetics of nucleation as well as guidance of mineralization on a particular bioactive surface.
Thanks for posting the paper! good-reading material~*
Aside from its short term biocompatibility, is there any particular reason why titanium was selected as the biomaterial of choice? In other words, since the titanium surface had to be modified, why not use another material? I suppose titanium is tried and true, and modifications to it would expedite FDA approval as oppose to using a whole new material in the graft but are there any other reasons you can think of?
Good job on a clearly written summary. Does the oxidation step help in preventing corrosion only, or does it also enhance biocompatibility?
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