New PhD Project Offers
2012-05-EM Magnesium-based biomaterials: From surface functionalization to cellular evaluation (IST-ICEMS, UPMC-LCMC)
Metal-based biomaterials are widely used in the area of bone repair implants, such as for bone screws and plates. Their key advantages are high mechanical properties that make them suitable for load bearing applications and easy preparation of large pieces with specific shapes by molding approaches. However, they currently suffer from two weak points: (i) their high density that can induce an unease of the patient and (ii) the extended corrosion at the contact of body fluids that may lead to the release of toxic species. Therefore current research aims at designing biomaterials from lighter elements and to limit, or at least to control, the in vivo degradation.
In this context, magnesium alloys present an attractive combination of properties including low density, elastic modulus and compressive yield strength close to natural bones and extremely good biocompatibility. The major drawback of Mg is that it corrodes very quickly in the physiological environment. However, this drawback can be converted in an important advantage: the Mg alloys can be used as temporary bioresorbable implants, avoiding the need of a 2nd surgery.By controlling the corrosion rate of the implant, the Mg ions, which are not toxic up to certain concentrations, are slowly released into the human body without deleterious effects. Therefore, after decades of developing strategies to minimise the corrosion of metallic biomaterials, there is now increasing interest in using an intentionally corrodible alloy in a number of critical medical devices. But, for this, the corrosion process needs to be controlled with accuracy, in such a way that the lifetime of the implant must be around some tens of months.
This control demands the development of new and effective strategies for surface processing and functionalisation in order to slowdown and to control the corrosion rate of Mg implants.Thus, we intend to develop hybrid biocompatible sol-gel coating with good barrier properties impregnated with sub-micron hydroxyapatite (HA) particles. Over this, a layer composed of natural bioorganic polymers will be deposited to increase affinity for cell attachment. This multilayered and multifunctional coating will slowly uptake fluids, forming conductive pathways that expose HA enhancing cell attachment and bone growth.
Figure 1 – (a) SEM image of sol-gel coating doped with bio compatible sub micron HA particles (from IST); (b) Cross-polarized light optical image of collagen films deposited on a glass surface (from UPMC)
Project Partners and their Roles
IST-ICEMS:development of the new surface coatings and control of corrosion mechanisms at localised level
UPMC-CMCP: surface bio-functionalization and in vitro evaluation
Industry Partner: Materials Engineers Group sp. z o.o. (MEG), Warsaw
