Abstract
A Ti-based alloy (Ti45Zr15Pd30Si5Nb5) with already proven excellent mechanical and biocompatibility features has been coated with piezoelectric zinc oxide (ZnO) to induce the electrical self-stimulation of cells. ZnO was grown onto the pristine alloy in two different morphologies: a flat dense film and an array of nanosheets. The effect of the combined material on osteoblasts (electrically stimulable cells) was analyzed in terms of proliferation, cell adhesion, expression of differentiation markers and induction of calcium transients. Although both ZnO structures were biocompatible and did not induce inflammatory response, only the array of ZnO nanosheets was able to induce calcium transients, which improved the proliferation of Saos-2 cells and enhanced the expression of some early differentiation expression genes. The usual motion of the cells imposes strain to the ZnO nanosheets, which, in turn, create local electric fields owing to their piezoelectric character. These electric fields cause the opening of calcium voltage gates and boost cell proliferation and early differentiation. Thus, the modification of the Ti45Zr15Pd30Si5Nb5 surface with an array of ZnO nanosheets endows the alloy with smart characteristics, making it capable of electric self-stimulation.
Highlights
To be considered as a permanent orthopedic implant, a material must fulfil various criteria
The surface of the alloy covered by zinc oxide (ZnO) nanosheets was much rougher, due to the lamellar structure produced by the high aspect ratio and smooth ZnO crystalline array showing a hexagonal sheet morphology, with an average thickness of 25 ± 8 nm (Figure 2c)
We demonstrated that the addition of Nb to the alloy enhanced osteoblast-like cell (Saos-2) adhesion and proliferation, and that cells grown onto the TiZrPdSiNb alloy presented higher levels of some late osteogenic markers during the first week in culture [45]
Summary
To be considered as a permanent orthopedic implant, a material must fulfil various criteria. Ti and its alloys (Ti6 Al4 V, Ti40 Nb) have been established as the most suitable biomaterials for permanent implants in certain applications (i.e., bone and joint replacements) because they exhibit superior mechanical properties, biocompatibility and corrosion resistance [6,7], when compared with other metallic implants, such as stainless steel or Co–Cr alloys [3,4,8] These alloys face some problems, such as the presence of non-desirable elements (e.g., Al and V in Ti6 Al4 V alloys [9,10]) or the mismatch between their Young’s. In view of this, ongoing investigations on Ti-based implants are focused on finding new compositions and designs to improve their performance [4,13,14,15]
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