MAGNETIC COLLAGEN-COATED HYDROXYAPATITE SCAFFOLD FOR BONE REGENERATION: FABRICATION, CHARACTERIZATION AND IN VITRO EVALUATION

Bone is a complex tissue that serves not only structural, but also important physiological functions. It has an inherent, well-regulated, regenerative capacity, however, in cases of severe fractures and excision surgeries it is often necessary to resort to bone substitutes to achieve optimal healing. Ceramic and polymeric scaffolds have been extensively studied for their regenerative capacity in many fields. Regarding bone, hybrid scaffolds that combine a hard and a soft material are the go-to since they mimic the natural tissue. Magnetism is also a great tool for bone regeneration. Scaffolds containing magnetic nanoparticles (MNP) exhibit a magnetic behavior when subjected to external magnetic fields, which modulates osteoblastic adhesion and proliferation, as well as progenitor differentiation, leading to improved osteointegration of the implant in vivo. In this work, a porous hydroxyapatite scaffold was produced and coated with collagen containing various percentages of superparamagnetic iron doped hydroxyapatite nanoparticles (FeHap2+/3+ NPs). The resultant scaffolds presented adequate interconnected porosity (70,8%), satisfactory mechanical properties and were able to form an apatite layer when immersed in simulated body fluid (SBF). Results obtained in the Resazurin assay showed that scaffolds containing MNP lead to higher metabolic activity of MC3T3-E1 pre-osteoblastic cells, and that this effect could be enhanced through the added influence of a static magnetic field (SMF). Confocal images of actin and nucleus staining imply that the SMF has a detrimental effect on cellular proliferation up to day 7, which might be related to an early differentiation start, triggered by the SMF. Nonetheless, at day 21 this was no longer perceived, and the magnetic field in combination with the MNPs, seemed to enhance the proliferation of the cells when compared with the sample without nanoparticles. Preliminary studies based on ALP staining also suggest that the materials containing nanoparticles support osteogenic differentiation, when in comparison with the control scaffold, without MNPs. The effect of the magnetic field in this assay was not evident. These findings suggest that the novel magnetic responsive scaffolds may be suitable candidates to be used for bone regeneration purposes.