Hierarchical Surface Pattern on Ni-Free Ti-Based Bulk Metallic Glass to Control Cell Interactions.

Ni-free Ti-based bulk metallic glasses (BMGs) are exciting materials for biomedical applications because of their outstanding biocompatibility and advantageous mechanical properties. The glassy nature of BMGs allows them to be shaped and patterned via thermoplastic forming (TPF). This work demonstrates the versatility of the TPF technique to create micro- and nano-patterns and hierarchical structures on Ti40Zr10Cu34Pd14Sn2 BMG. Particularly, a hierarchical structure fabricated by a two-step TPF process integrates 400 nm hexagonal close-packed protrusions on 2.5 µm square protuberances while preserving the advantageous mechanical properties from the as-cast material state. The correlations between thermal history, structure, and mechanical properties are explored. Regarding biocompatibility, Ti40Zr10Cu34Pd14Sn2 BMGs with four surface topographies (flat, micro-patterned, nano-patterned, and hierarchical-structured surfaces) are investigated using Saos-2 cell lines. Alamar Blue assay and live/dead analysis show that all tested surfaces have good cell proliferation and viability. Patterned surfaces are observed to promote the formation of longer filopodia on the edge of the cytoskeleton, leading to star-shaped and dendritic cell morphologies compared with the flat surface. In addition to potential implant applications, TPF-patterned Ti-BMGs enable a high level of order and design flexibility on the surface topography, expanding the available toolbox for studying cell behavior on rigid and ordered surfaces.

Potential of Laponite® incorporated oxidized alginate-gelatin (ADA-GEL) composite hydrogels for extrusion-based 3D printing.

The concept of adding inorganic fillers into hydrogels to form hydrogel nanocomposites often provides advantageous properties which can be exploited for successful 3D biofabrication. In this study, a new composite hydrogel combining oxidized alginate-gelatin (ADA-GEL) hydrogel and Laponite® nanoclay as inorganic nanofiller was successfully developed and characterized. The results showed that the addition of 0.5% (wt/vol) Laponite® nanoplatelets improved the printability of ADA-GEL hydrogels enabling the fabrication of detailed structures since a low effect of material spreading and reduced tendency to pore closure appeared. Furthermore, a comparison of different needle types (cylindrical and conical; same inner diameter of 250 µm) in filament fusion test showed that the pattern dispensed by cylindrical tip has enhanced printing accuracy and pattern fidelity when compared with the pattern from conical tip. A glass flip test determined a processing window of 1-2 h after composite ink preparation. Overall, Laponite® /ADA-GEL hydrogel composites are confirmed as promising inks for 3D bioprinting.