New generation biomedical materials for bone tissue regenerative nanomedicine

The evolution of biomedical materials passed a long way, from minimally toxic bioinert ones (first generation of biomaterials) to resorbable or bioactive, able to elicit a controlled reaction in physiological conditions (second generation). These biomaterials ranged from metals and alloys to ceramics, polymers, bioglasses and their composites. In those cases, the goal was to prepare biomimetic synthetic materials, i.e. possessing characteristics (composition, physico-chemical and mechanical properties) similar to those of the natural tissues. The next step was to overcome the intrinsic limits of synthetic materials, changing paradigm and passing to the activation of cells and genes, i.e. to the third generation of biomaterials. In terms of modern bone materials it means that material should be osteoconductive, osteoinductive and able to integrate into the native tissue. The nowadays biomaterials design implies the development of properly engineered three-dimensional architecture scaffolds aimed to replace and/or to repair and to regenerate damaged tissues, possessing necessary mechanical characteristics, able to host proteins, various drugs and active principles, to form strong bonds with host living tissues and to support bone cells proliferation, growth and differentiation. Moreover, current challenge in biomaterials science is to match the kinetics between the biomaterial's degradation and newly formed tissue growth, triggering the effective development of the latter. To achieve this goal, the main trends were directed to calcium phosphate based bioceramics, proposed for various bone implant applications [1-3]. However, to give rise to such responses, bioactive glasses and glass ceramics are more suitable, with respect to the traditional hydroxyapatite and its derivatives, manifesting much more bioactive effect [4]. Recently, an increasing interest has been focused on bioactive glasses, resulting to be suitable candidates for the realization of porous three-dimensional structures, able to carry growth factors, to support and to activate bone cell growth. The ability of bioglasses to form strong bonding with the host bone tissue is attributed to the ion release, taking place upon contact with physiological fluids, stimulating osteoblasts differentiation and growth. For compositional variation, bioactive glasses and glass-ceramics are prepared by the sol-gel synthesis procedure, being this method suitable for the realization of interconnected micro and nanocrystalline component networks. Following this way, the quality and quantity of additional phases can be controlled during the production phase, and the structure and composition of bioglasses can be tailored, adapting them for a broad rage of applications and matching their degradation rate and the velocity of ion release to the local tissue request and new tissue growth. References: [1] J.V. Rau, I. Cacciotti, A. De Bonis, M. Fosca, V. Komlev, A. Latini, A. Santagata, R. Teghil, "Fe-doped hydroxyapatite coatings for orthopaedic and dental implant applications", Applied Surface Science, vol. 307, pp. 301-305, Apr. 2014. [2] J.V. Rau, M. Fosca, I. Cacciotti, S. Laureti, A. Bianco, R. Teghil, "Nanostructured Si-substituted hydroxyapatite coatings for biomedical applications", Thin Solid Films, vol. 543, pp. 167-170, Aug. 2013. [3] M. Fosca, V.S. Komlev, A.Yu. Fedotov, R. Caminiti, J.V. Rau, "Structural study of octacalcium phosphate bone cement conversion in vitro", ACS Applied Materials and Interfaces, vol. 4 (11), pp. 6202-6210, Oct. 2012. [4] M. Ledda, A. De Bonis, F.R. Bertani, I. Cacciotti, R. Teghil, M.G. Lolli, A. Ravaglioli, A. Lisi, J.V. Rau, "Interdisciplinary approach to cell-biomaterial interactions: biocompatibility and cell friendly characteristics of RKKP glass-ceramic coatings on titanium", Biomedical Materials, vol. 10 (3), pp. 035005 (7), June 2015.