  The inclusion of small amounts of copper is often reported to enhance the
mechanical and biointegrative performance of bioceramics towards tissue
engineering applications. In this work, 3D scaffolds were additively
manufactured by robocasting of precipitation derived copper doped diopside.
Compositions were chosen in which magnesium sites in diopside were substituted
by copper up to 3 at.%. Microstructure, mechanical performance, bioactivity,
biodegradability, drug release, biocompatibility, in vitro angiogenesis and
antibacterial activity were studied. Results indicate that copper is
incorporated in the diopside structure and improves materials fracture
toughness. Scaffolds with more than 80% porosity exhibited compressive
strengths exceeding that of cancellous bone. All compositions showed
bioactivity and drug release functionalities. However, only samples with 0 to 1
at.% copper substitution showed favorable proliferation of osteogenic sarcoma
cells, human umbilical vein endothelial cells and fibroblasts, while larger
amounts of copper had cytotoxic behavior. In vitro angiogenesis was
significantly enhanced by low levels of copper. Copper containing materials
showed anti Escherichia coli activity, increasing with copper content. We show
that across multiple indicators, copper substituted diopside of the composition
CaMg0.99Cu0.01Si2O6, exhibits high performance as a synthetic bone substitute,
comparing favorably with known bioceramics. These findings present a pathway
for the enhancement of bioactivity and mechanical performance in printable
bioceramics.
