Promoted osteogenesis on calcium modified surface of stainless-steel lattice produced by selective laser melting

Stainless steel has been widely used as an implant material for its good biocompatibility, suitable mechanical strength, and high corrosion resistance<i>in vivo</i>. However, its biomedical applications suffer from delayed healing due to its high density and stiffness. Here we proposed body-centered cubic lattice structures with various unit sizes to adjust the density and stiffness of 17-4 PH stainless steel implants to simulate the bone structure and mechanical performance. The mechanical properties satisfy the requirement to be used with the human body with a yielding strength over 60 MPa and Young's modulus over 1.7 GPa. Corrosion resistance characterization indicates that the implants have negligible changes in microstructures and mechanical properties in simulated body fluid for 6 months. The implants were modified by inserting calcium sulphate-based bone cement into the voids of the lattice to improve their biocompatibility. Cytotoxicity results showed that both the implants and modification have no toxicity to human bone marrow mesenchymal stem cells.<i>In vivo</i>safety and osseointegration testing of the implants were conducted by implantation in rabbit distal femur, showing an improved recovery and bone integration of the implants. The presence of calcium sulphate and tailored lattice structure synergistically promotes osteogenesis through controlled calcium ions release and matching the mechanical properties of the bone.