Post forming analysis and in vitro biological characterization of AZ31B processed by incremental forming and coated with electrospun polycaprolactone

Main problems related to the adoption of magnesium alloys for temporary orthopedic prostheses manufacturing are (i) the need of an efficient production process and (ii) the high corrosion rate compared with the bone healing time. In this work, the single-point incremental forming (SPIF) process, an effective and flexible solution for manufacturing very small batches even composed by one piece, was investigated. Tests were conducted on AZ31B-H24 sheets and were aimed at understanding the effect of temperature on the mechanical characteristics (microstructure, hardness, and roughness) of the sheet after the above-mentioned forming process and their correlation with both the corrosion rate and the cytocompatibility. In addition, after the forming process, samples processed by SPIF were coated by electrospun polycaprolactone (PCL) to reduce the corrosion rate and to further improve the cytocompatibility. Grain refinement was achieved thanks to the combined effect of temperature and strain rate during forming and finer grain size resulted to improve the magnesium corrosion resistance. In simulated body fluids, the electrospun PCL-coated samples exhibited a slower pH increase compared with uncoated samples. No indirect cytotoxic effects were detected in vitro for MC3T3-E1 cells for both coated and uncoated samples. However, cells colonization was observed only on electrospun PCL-coated samples, suggesting the importance of the polymeric coating in promoting the adhesion and survival of seeded MC3T3-E1 cells on the implant surface.