Maddalena Mastrogiacomo

Inspired Porosity for Cells and Tissues

The use of 3D scaffolds provides an adhesive substrate that become the physical support matrix for in vivo tissue regeneration. In the last few years t he use of bioengineered 3D scaffolds is becoming the most promising experimental approach for the regenerati o of living tissue. Stem cells are used to study the signaling pathways that mediate cel l diff rentiation and to identify optimal microenvironments that support cellular functionality. For tiss ue engineering applications 3D biomaterials must be able of supporting the functional properties of o teogenic cells. Inorganic devices are particularly relevant for bone regeneration; in partic ular alcium phosphate ceramics have been shown to interact strongly particularly with bone. The aim of the present work was the design and the production of a 3D Calcium/Phosphate scaffold able to mimi cs the in vivo environment to induce/promote tissue repair; the scaffold developed shows a defined design able to achieve the required functionality. Introduction Porous ceramic are interesting candidate materials for hard ti ssue engineering; bone is a natural composite in which mineral crystal are enclosed: hydroxyapatite (HA) i n bone provides a natural 3D scaffold with organic fibrous material. The current trend of hard ti ssue engineering is toward the development of bioceramics and in particular porous calcium phosphates are u ed. In particular porous ceramics can be designed in term of porosity and pore size dis tribution [1, 2]. The micro and macro architecture of the scaffold is highly dependent on the producti on process and the aim of the present development is to provide a structure able to host and intera ct with cells, to induce/promote cells proliferation, differentiation and new bone deposition/f ormation. With appropriate modification, traditional ceramic manufacturing technique ( slip casting) can be used to achieve innovative scaffold structure. In this paper, our achievements in term of characterization parameters of the developed scaffold are reported; the device functiona lity was also investigated loading the scaffold with stem cells [3, 4], in vivo experimental results are described. Materials and Methods The porous devices were prepared with an innovative technology using slurry expansion: a slurry with high powder concentration was used and expanded in a known volume to achieve a total porosity close to 80 vol. %; the porosity is characterised by bimodal por ous structure and controlled morphology. Physico-chemical and morphological characterisation of the de velop d 3D scaffold were carried out; closely examination, from the morphological point of view was performed to investigate the design of the micro-macro porosity and the pore size distribution. The porosity distribution was investigate with an Image analyser; the analys es was carried out following ASTM E562 (Leica Imaging System Ltd. Q500MW by Qphase Application); morpholog y was analysed by SEM,(Leica, Cambridge) while phases investigation and chemical a nalyses were carried out Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 1095-1098 doi:10.4028/www.scientific.net/KEM.254-256.1095

Bone Regeneration and Bioengineering

Large bone defects (critical-size defects) caused by disease, trauma, or tumor resection are not healed by the intrinsic regenerative capacity of bone and remain one of the more difficult regenerative therapies to successfully achieve. During the last two decades, major progresses have been made with regard to the in vitro fabrication of bone substitutes starting from suitable scaffolds, mainly resorbable porous ceramics, seeded with autologous (from the same patient) osteogenic cells, such as bone marrow–derived mesenchymal stem cells. The use of these ex vivo tissue engineered constructs is highly limited because of the difficult logistic of collecting the cells from the patients, expanding them in culture, and returning them to the surgical theater and because of the high cost of the culture procedure requiring the use of GMP facilities in order to cope with the strict rules defined by the European and National Regulatory Agencies. As a result, the classical tissue engineering approach involving ex vivo expanded patient cells should be confined only to extreme life or organ-saving situations. n nThe rapidly developing knowledge about the pathways occurring during the healing process provides information about the natural response of the body to injury. This suggests a novel approach based on the activation of the endogenous regenerative capacity of the tissue itself. The endogenous regenerative potential correlates with the presence in the tissues of a population of stem/progenitor cells, responding to exogenous signal to generate a progeny of differentiated cells repairing or rebuilding the tissue. Differently from the “traditional” tissue engineering scheme, an endogenous regeneration strategy aims at the stimulation of the intrinsic potential of a tissue to heal or regenerate by using “off-the-shelf” standardized bioactive biomaterials without cells. n nIn an effort to mimic the natural microenvironment during wound healing, the integration of different growth factors and cytokines into the scaffolds has been proposed. More recently, the idea of integrating a physiological cocktail of factors into the scaffold to lead tissue regeneration and to reduce morbidity and recovery time took place. In the arena of sustained multiple growth factor delivery, platelet-rich plasma (PRP) is a valid contender. It can deliver a high concentration of multiple growth factors in the “right” composition and in the “right” relative concentrations using a low cost strategy.