Laser Patterning of 3D Printed Near-Beta Ti Alloy for Modulated Response of Human Bone Marrow Stromal Cells

Additive Manufacturing (AM) of low modulus beta-Ti alloys paves the way for patient-specific implants which reduce stress shielding and, laser surface functionalization has a high potential to improve bone healing processes. The presented project aims to design a laser-based processing chain for a beta-type Ti alloy with (i) AM of 3D parts with defined microstructures and (ii) surface texturing with direct laser interference patterning (DLIP). <i>In vitro</i> studies with human bone marrow stromal cells clarify how those tailored textures guide the cell response. Ti-13Nb-13Zr parts are fabricated by laser powder bed fusion (LPBF) and microstructure - mechanical performance relations are studied. DLIP with nanosecond (ns) and picosecond (ps) pulses generates single- and multi-scale surface topographies in micro- and nano-meter ranges, respectively. These surface textures are analysed with confocal laser scanning microscopy, electron microscopy and Auger electron spectroscopy and their impact on wettability and corrosion behavior in phosphate buffered saline is studied. Their influence on the behavior of human bone marrow stromal cells is assessed with fluorescence microscopy, electron microscopy and MTS assays. The enzyme activity of tissue non-specific alkaline phosphatase activity serves as early osteoblast differentiation marker.<br/>The ns-DLIP textured surfaces exhibit high beta-phase fractions and thick passive films which enhance the corrosion stability compared to ps-DLIP ones. Compared to untextured specimens, both types of DLIP textures cause higher metabolic activity and cell proliferation. The single-scale ns-DLIP textures encourage cell extensions anchored in grooves, while multi-scale ps-DLIP textures promote cell extensions attaching to nanostructures on walls. The groove width and nanotopographies in groove areas facilitate cell spreading. Combined effects of surface topography, roughness and chemistry influence cell adhesion, proliferation, and differentiation. Surface-functionalized 3D printed beta-Ti alloys hold potential for a novel generation of biocompatible implants. Funded by EFRE, Parliament of Saxony (100382988/-89), EC (H2020-BIOREMIA, GA 861046).