Specifically, the experts included fragments of proteins that the body produces naturally, known as fibronectins, which encourage the binding of bone cells to the implant. These molecules cause the cells to grow and proliferate, resulting in greater acceptance of the external element. Leonor Santos-Ruiz, a researcher at the University of Malaga and one of the authors of the article, declared to Fundación Descubre: ‘The integrins of the cells function as perfect hooks that attach themselves to the fibronectin fragments introduced into the dendrimer structure, achieving a robust integration between the implant and the organism.’
In this way, each branch of the scaffold becomes attached to the bone with these hooks, thereby anchoring the implant and assisting the connections to occur naturally thanks to the integration of the metal with the living tissue. ‘These unique properties make dendrimeric systems suitable for a wide variety of applications in regenerative medicine,’ added the researcher.
Thus, in addition to fibronectins, other substances could be incorporated, such as anti-inflammatory substances, which favour tissue recovery after the installation of the prosthesis, or antibiotics, to avoid frequent problems in current implants, such as bacterial infections.
Implants turned into bone
The problems resulting from replacements with metal material are usually due to overloading, which can lead to the loss of healthy bone, wear and tear of the implant itself, or a poor bone-implant interaction that results in rejection or infection.
The experts are already working to confirm the suitability of its use in patients such as has been demonstrated in the laboratory. In addition, they consider it a viable and applicable option for dental implants, and for full jaw, hip or knee prostheses. ‘The latter currently have a working life of about 10 years. With this new structure the duration would be longer,’ concluded the researcher.
The work of these experts modified the surfaces of the dendrimers with the fragment of fibronectin known as ‘RGD domain’, which consists of only three amino acids (arginine, glycine, and aspartate) that serve as an anchor for the cell membrane receptors called integrins. These receptors transmit to the cells numerous crucial signals about the surrounding environment and determine whether or not the cell can adhere to a particular material.
The metals, polymers and synthetic products used to make today’s prostheses lack the RGD domain, since they are not biological materials, and therefore it is difficult for the cells to recognize them. When the metal is coated with a dendrimer bearing the RGD domain, the cell finds an anchor point in that metal and binds to it naturally. This composition has therefore favoured and improved cellular adhesion to titanium surfaces, which increases its biocompatibility, that is, its ability to be accepted by the organism. By doing so, the dendrimer is fixed to the bone, which interprets it as a part of itself and not as something alien, and both the implant and the place where it is installed are able to speak the same ‘biological language’ and there is no rejection.
This work was supported through the Spanish Ministry of Science and Innovation projects ‘New dendrimers and fluorescence markers for biomedical applications’ and ‘Customized bioengineered porous titanium implants for maxillofacial reconstructive surgery. Proof of concept and preclinical testing’, and through the Regional Government of Andalusia’s Department of Health and Families projects ‘Development of New Nanobiosensors for the Diagnosis of Adverse Drug Reactions’ and ‘Repair and Regeneration of Mandibular Segmental Bone Defects. Preclinical Model Based on Tissue Engineering’.