Bone implants made of combined material
Finnish and Russian scientists have developed bone skeletons for the treatment of bone injuries
Tatiana Perevyazova, ITEB RAS Press Service
Over the past few years, scientists have been developing a new, promising strategy in the field of regenerative medicine, which is based on tissue engineering. The main objective of this strategy is the construction and cultivation of living tissues or organs capable of functioning normally outside the body. They are grown for subsequent transplantation to patients – either for replacement or for more effective treatment of various body injuries.
Scientists from the University of Helsinki (Finland) and the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences (Russia) have developed bone skeletons recognized as promising materials in the field of bone tissue engineering. The results of their research were published in January 2018 in the International Journal of Pharmaceuticals International Journal of Pharmaceuticals (Ezazi et al., Conductive vancomycin-loaded mesoporous silica polypyrrole-based scaffolds for bone regeneration).
Tissue engineering is a new field of science combining the latest achievements of biomedicine, pharmacology and materials science. Advances in bone tissue engineering make it possible to correct various widespread clinical problems associated with bone defects.
Scientists propose new approaches that are alternative to previous methods using auto– and allografts. The engineering of bone skeletons makes it possible to restore the porous 3D structures of damaged bones and their physiological functions. Due to this, the successful regeneration of new bone tissue cells takes place and the influx of nutrients to the damaged area is ensured, which increases the likelihood of its successful cure.
Finnish and Russian scientists have developed bone skeletons consisting of hydroxyapatite, gelatin, polypyrrol and mesoporous silicon oxide, which, due to their excellent biocompatibility, osteoconductivity and the potential for targeted drug delivery, are of great interest for bone tissue engineering.
Synthetic hydroxyapatite is already widely used in bone tissue engineering for the reason that its chemical composition is similar to hydroxyapatite in bone. Biocompatibility, osteoconductivity and stimulation of bone regeneration processes make this substance an ideal component for bone skeletons. But hydroxyapatite has a significant disadvantage for bones – fragility and, accordingly, poor mechanical properties.
Another component used by researchers to create frameworks, silicon dioxide, also has a high potential for inducing mineralization processes. This substance can also be used as a vehicle for drug delivery followed by controlled release.
Another component of the scientists' development is gelatin, with its remarkable ability to attach osteoblasts, young bone cells that form regenerating bone tissue.
A conductive polymer, polypyrrol, binds all these components. It has electrical and thermal stability, but it also has serious disadvantages – fragility, poor mechanical properties and lack of biodegradability. However, in combination with other materials used by researchers to create bone skeletons, polypyrrol can be used without any toxic effects on osteoblasts.
Samples of materials based on gelatin, mesoporous silica gel, hydroxyapatite and polypyrrole (+PP). An image of the surface of the material obtained using scanning electron microscopy (SEM). Photo provided by Yuri Shatalin.
The simultaneous use of such a combination of substances to create bone skeletons allowed the researchers to improve the properties of the selected materials to accelerate bone regeneration and at the same time to prolong the release of antibacterial substances up to 4 months from the moment of administration.
"The properties of the obtained materials were compared in different experiments, in which frameworks containing polypyrrol demonstrated good mechanical properties, higher protein adsorption and a higher percentage of release of the model antibiotic – vancomycin for a long time, compared with non–conductive frameworks," comments one of the authors of the work, senior researcher at the ITEB Laboratory of Tissue Engineering RAS, Candidate of Biological Sciences Yuri Shatalin. – Osteoblasts, bone tissue cells placed in the materials under study, remained viable for 14 days, which suggests their good biocompatibility."
Thus, scientists have created new conductive composite bone skeletons, and their results fully confirm their applicability in targeted drug delivery and the prospects for further research of these materials in various tissue engineering applications and regenerative medicine of the future.
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