In Vitro Bone Cell Behavior on Porous Titanium Samples: Influence of Porosity by Loose Sintering and Space Holder Techniques

Abstract

A great variety of powder metallurgy techniques can produce biomimetic porous titanium structures with similar mechanical properties to host bone tissue. In this work, loose sintering and space holder techniques, two frequently used metallurgical techniques, are compared to evaluate the influences of porosity (content, size, morphology and wall roughness), mechanical properties (stiffness and yield strength) and in-vitro cellular responses (adhesion and proliferation of myoblasts and osteoblasts). These comparisons are made to achieve the best balance between biomechanical and bifunctional behavior of a partial porous implant for cortical bone replacement. Cell adhesion (filopodia presence) and spreading were promoted on both porous surfaces and fully dense substrates (non-porous control surfaces). Porous scaffold samples designed using 50 vol.% NaCl space holder technique had an improved bioactive response over those obtained with the loose sintering technique due to higher roughness and scaffold pore diameter. However, the presence of large and heterogeneous pores compromises the mechanical reliability of the implant. Considering both scenarios, the substrates obtained with 40 vol.% NH4HCO3 and pore size ranges between 100 and 200 μm provide a balanced optimization of size and strength to promote in-vitro osseointegration.

Use of Impedance Spectroscopy for the Characterization of In-Vitro Osteoblast Cell Response in Porous Titanium Bone Implants

“…This also favors the matrix deposition on porous surfaces developing a mature ECM (extracellular matrix). Proof of this cellular behavior has been described in previous studies of our group using NH4HCO3 porous substrates using 50% of spacer particles [39,50]. At day 21, it can be observed a cell monolayer of highly differentiated osteoblast on 40 vol.% (100-200 µ m) sample with deposition of hydroxyapatite vesicles which also corroborates the advanced mineralization stage of osteoblast in this porous surface.…”

“…Finally, electrical impedance spectroscopy technique [50] was used initially to assess and corroborate the porosity obtained and later to characterize osteoblast cell culture growth on the porous titanium discs (porous and fully-dense; see details in the Section 2.3.5). The equipment used to perform the electrical impedance measurements was the Hewlett-Packard 4395A, which is a network, spectrum and impedance analyzer, available at IMSE-CNM-CSIC (Instituto de Microelectrónica de Sevilla, Seville, Spain).…”

Improved Corrosion Behavior and Biocompatibility of Porous Titanium Samples Coated with Bioactive Chitosan-Based Nanocomposites

“…Several authors have also reported that porosity has a strong influence on the cell viability, adhesion, proliferation and differentiation of an osteoblast [ 54 , 55 ]. The increased roughness values inside the pores and the increased surface contact area of porous samples may promote a higher density of osteoblast cells compared to the dense ones [ 56 ].…”

Estudio de biocompatibilidad y osteointegración de nuevos materiales protésicos

“…In the images obtained by SEM, we observed that at 7 days the cells covered the entire surface of the discs, cell growth occurred equally in both samples and they reached cell confluence, and the lowest activity was consistent with the images cells that are starting the mineralization process. In addition, we began to observe the secretion of material that will form the extracellular matrix by the osteoblasts, and an increase in molecules with the appearance of hydroxyapatite was observed on the surface of the cells 21 . On the other hand, osteoblasts presented filopodia and lamelopodia, essential cellular structures during the cell adhesion process, which indicates that the union to other cells and to the material is direct; other authors describe these junctions in MC3T3 cells and Ti discs c.p.…”