Nanotubes for strengthening artificial bone
Scientists at Rice University (Houston, Texas) and Radboud University (Nijmegen, the Netherlands), working under the guidance of Professor Antonios Mikos, have demonstrated that the use of frameworks made of porous material, permeated with carbon nanotubes, allows to grow bone tissue of increased density.
To grow bone, tissue engineering specialists usually sow bone cells on a porous biodegradable material that acts as a framework. The correct selection of chemical and physical stimuli ensures the formation of a full-fledged bone tissue framework in place of the collapsing in the body.
The ideal frame had to be highly porous, non-toxic, biodegradable and at the same time strong enough to withstand the structural load of the bone, which would replace it later. The results of earlier studies indicate that the addition of carbon nanotubes provides additional strength to the frame, however, the authors tested this material on animals for the first time.
As part of the experiment, scientists implanted rabbits with two types of skeletons. Frames of one type were made of biodegradable poly(propylene fumarate) plastic – PPF – which demonstrated good results in earlier works. The frames of the second type consisted of 99.5% PPF and 0.5% single-walled carbon nanotubes. Typically, the length of nanotubes is about 1000 times larger than the diameter, but the authors used shorter segments that have proven themselves well in testing for cytocompatibility.
The condition of 50% of the samples was analyzed 4 weeks after implantation, and the remaining 50% – after 12 weeks. In the first case, there were no significant differences between implants of different types, however, after 12 weeks, nanotube-containing implants contained an amount of bone tissue corresponding to about 2/3 of the mass of bone tissue of normal bone, while for polymer implants this figure was only 1/5.
According to the authors, the results exceeded all expectations. The mechanisms of the positive effect of nanotubes are still unclear, but the authors are actively studying the issue.
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