Bone biosynthesis

Edit Hook

To make bone, nature starts with a matrix of collagen fibrils, which possess the remarkable ability to nucleate the growth of hydroxyapatite crystals in such a way that the long axis of the crystal is parallel to the fiber axis. Aligned arrays of these nanocrystals grow among the collagen fibrils, stiffening the matrix, creating bone. Samuel I. Stupp and his associates at Nanotope have recently developed a class of molecules that could be used to direct the growth of bone in a way that mimics the natural formation. The molecules, called peptide amphiphiles, contain a short peptide head, a peptide linker region, and a hydrophobic fatty acid tail. When a solution containing these peptide amphiphiles is injected into a physiological environment, they form long tubular scaffolds with the peptide head exposed on the surface. Properly designed peptide heads are able to act as growth factors and promote the adhesion of host cells which form structures such as bone. Moreover, the cells are spatially directed by the scaffold tubule so that the biomineralized material (in the case of bone) is structurally similiar to its natural counterpart. This approach involves mimicry of the natural collagen scaffold animals produce to guide bone formation. However, the artificial method could be used to promote bone growth after injuries that would never naturally occur. Moreover, the variability offered by the peptide head of the peptide amphiphiles makes the same technique viable for directing the regrowth of other tissue like nerve cells.

Key Differentiators

If a time ever comes when biomimetic bone regrowth treatments are commonplace, currently used methods of healing bone damage (casts and implants) will seem crude and medieval. Nanoscale techniques like those developed by Dr. Stupp are simply more precise.

Biomimicry Story

Dr. Samuel Stupp made a name early in his career as a materials scientist developing self-assembly products (often used for industrial purposes). His real journey began in 1995 when a research approach went 'wrong' and he accidently revealed the principles to building nanofibers (useful in biological processes such as those discussed above).  His discovery sparked an interest across a broad range of professionals- securing him a spot as a researcher in Northwestern's materials-science program.  The recognition of his 'limited' knowledge in biology and clinician fields allowed Dr. Stupp to humbly recruit scientists dedicated to specific fields that would allow his research to grow in many directions with a depth unlike most projects. "It's always easier when you specialize in something, and there is a place for that," he continues. "But if you're trying to solve these kinds of problems, you cannot do it without interdisciplinary research" (Svoboda 2011: 1). Dr. Stupp began collecting a diverse team of intellects- ranging from chemists to physicists to neurosurgeons- to help him pursue the idea of utilizing nanomolecules in biological repair processes.  It is through this interconnected approach that Dr. Stupp, in collaboration with Dr. Jack Kessler (a neuroscientist at Northwestern), was able to develop a nanofiber that cured partial-paralysis in mice.  "The beauty of this approach," Stupp says, "is that it just involves injecting something that looks like water" (Svoboda 2011: 2).  From his interconnected research method to his research design, Dr. Stupp provides a perfect example of the extent to which biomimicry can be applied.  Acting just as much as a teacher as he does as an innovative researcher, Dr. Stupp has inspired a vast amount of colleagues, undergraduate students, graduate students, etc. to push the boundaries of their scientific comfort zones.  By bridging the gap between scientific fields, a whole new world of research becomes available- an idea that has allowed this biomimetic innovator to discover life-changing designs!

Challenges Solved

Treating bone injuries (e.g. fractures) usually involves setting the bone in place so that natural processes can mend the damage. Malformation of the regrown bone is common since there is essentially no way to guide the nano-scale formation of the bone mineral. Other techniques involving metal implants are sometimes used to replace especially damaged bone. Artificially guided regrowth of bone using peptide amphiphiles developed by Nanotope may someday be a common technique for treating bone damage since it is conceptually capable of producing perfectly formed bone.

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