Surface treatments and pre-calcification routes to enhance cell adhesion and proliferation

When coated with a bone-like apatite layer, biodegradable polymers have a great potential to be used as bone-repairing materials, since they can exhibit not only mechanical properties analogous to the natural bone but also a bioactive character. Presently available methods to produce such type of coatings are usually difficult to control on what concerns to the calcium-phosphate (Ca-P) layer composition, resorbability, and ability to generate strong bonds with substrates. On the other hand the presently available methodologies are not so effective on coating, 3D architectures for being used as tissue engineering scaffolds. These are some challenges addressed in our work. In that perspective, our research group is developing several biomimetic coating methodologies, inspired in natural physiological processes, to coat the surface of starch based biodegradable polymers with tailored apatite layers that win be able to bond to living bone. The different biomimetic approaches that are being proposed go from adaptations of the traditional biomimetic methodology (performed for untreated and surface modified materials using chemical and physical means) to innovative sodium silicate gel treatments or a novel autocatalytic methodology. To understand the mechanisms of apatite formation, particularly in the earlier stage of nucleation, the atomic force microscopy (AFM) has been used as an extremely powerful tool, since it allows for in-situ studies of the surface, simulating the chemical environments founded in-vivo. The recent developments on tissue engineering in the field of orthopaedic research allow for creating an engineered living tissue. However, it is required the attachment, proliferation and differentiation of living cells on the surface of appropriate polymeric scaffolds. In this case, surface modifications have an important role, since they can improve the cell adhesion and proliferation at the surface of materials. Therefore, plasma and chemical induced graft polymerisation of active groups on starch based blends is another approach proposed by our group in order to achieve this goal. Preliminary cell adhesion and proliferation tests, carried out in materials on which acrylic monomers have been grafted, have shown remarkable improvements with respect to original starch based samples.