Masataka Hakamada

The bioengineering of three-dimensional (3D) tissues, such as spheroids and organoids, has transformed regenerative medicine, offering in vitro platforms for transplantation and drug screening. Typically, spheroids and organoids range from 50 to 200 μm in size. Larger 3D tissues (several millimeters) with high cellular density (≥10⁸ cells/cm³) enable the development of complex tissues containing vascular networks that closely mimic in vivo environments. However, fabricating such tissues is challenging due to oxygen and nutrient limitations. This study demonstrates the development of millimeter-sized 3D in vitro tissues with high cellular density through triculture with pericytes, 3D printing, and shaking culture. These three steps enabled the rapid formation of mature hierarchical vascular networks, integrating artificial channels and capillaries to supply oxygen and nutrients. Pericytes facilitated vasculogenesis and promoted anastomosis between artificial channels and capillaries. This work offers novel approaches to scale-up in vitro tissue models with vascularized networks for tissue engineering applications.

T6-tempered A6061 aluminum alloy sheets were edge joined using electrodeposited copper. Anodic oxidation of the aluminum alloy substrates improved the resulting join strength. This observation is attributed to the nanoanchor effect—mechanical interlocking between the nanoporous structure of anodic aluminum oxides (AAOs) and the electrodeposited copper. A tensile join strength of 214 MPa was obtained when the sheets were joined in an electroplating bath containing thiourea. The microstructures at the AAOs/copper interface were observed using scanning and transmission electron microscopies to elucidate the underlying mechanism of the high join strength. Mechanical strengthening of the electrodeposited copper is necessary for further strengthening of the joint.

A new CFRP-aluminum joining method has been developed by Cu electrodeposition. Cu deposition was filled into the roughened CFRP surface and the significant anchor effect was attained by the joining method. As a result, CFRP and A6061 Al alloy were successfully joined by Cu electrodeposition and a high joining strength of 67 MPa was obtained.

Nanoporous Au exhibits high antibacterial activity (AA) without releasing reactive oxygen species or metal ions, instead its AA depends on the work function (WF) because cell walls are affected by peculiar electronic states at the surface. Based on this mechanism, a flat surface without nanostructure should show high AA if the WF of the surface is suitably tuned. To verify this, ultrathin Pt islands with high WF was fabricated on flat Au by underpotential deposition (UPD) of copper and subsequent redox replacement with Pt, and the AA of the Pt/Au substrate on Escherichia coli was evaluated. The Pt/Au substrate showed higher AA than Pt and Au surfaces, and a positive relationship between AA and WF was demonstrated. In addition, first principles calculations were performed to investigate the mechanism for the high WF of the Pt/Au substrate. The findings suggest that the high WF of the Pt/Au substrate is at least partly due to charge transfer from Au to Pt.