Cellular response of osteoblasts to low modulus Ti-24Nb-4Zr-8Sn alloy mesh structure.

Titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) are widely used for implants, which are characterized by high elastic modulus (∼110 GPa) with (α + β) structure and that may induce undesirable stress shielding effect and immune responses associated with the presence of toxic elements. In this regard, we have combined the attributes of a new alloy design and the concept of additive manufacturing to fabricate 3D scaffolds with an interconnected porous structure. The new alloy is a β-type Ti-24Nb-4Zr-8Sn (Ti2448) alloy with significantly reduced modulus. In the present study, we explore the biological response of electron beam melted low modulus Ti2448 alloy porous mesh structure through the elucidation of bioactivity and osteoblast functions. The cellular activity was explored in terms of cell-to-cell communication involving proliferation, spreading, synthesis of extracellular and intracellular proteins, differentiation, and mineralization. The formation of fine apatite-like crystals on the surface during immersion test in simulated body fluid confirmed the bioactivity of the scaffold surface, which provided the favorable osteogenic microenvironment for cell-material interaction. The combination of unique surface chemistry and interconnected porous architecture provided the desired pathway for supply of nutrients and oxygen to cells and a favorable osteogenic micro-environment for incorporation (on-growth and in-growth) of osteoblasts. The proliferation and differentiation of pre-osteoblasts and their ability to form a well mineralized bone-like extracellular matrix (ECM) by secreting bone markers (ALP, calcium, etc.) over the struts of the scaffold point toward the determining role of unique surface chemistry and 3D architecture of the Ti2448 alloy mesh structure in modulating osteoblasts functions.