Add2MechBio

Add2MechBio project intends to design and fabricate innovative implants for orthopedic applications. Gathering an additive manufacturing technology for the necessary fabrication freedom with a true understanding of the effect of mechanical loading on bone cells mechanisms (mechanobiology), this project intends to fill an existing gap on commercial implants – the need to foresee the necessary stress/strain to effectively stimulate the host bone and elicit a biological response close to that found in natural bones. Over the years, the number of patients undergoing total hip and knee arthroplasties has been increasing. Due to the increased life expectancy and aging population this trend is expected to continue and the number of patients that will outlive their first prosthesis will also rise (patients that will need revision surgeries). These implants impaired fixation (commonly known as aseptic loosening) is one of the main reasons for revision surgeries, being caused by a diminished mechanical stimulation at the implant-contacting bone, when compared to the normal physiological bone stimulation. It is well established in the scientific medical and engineering community that this phenomena is due to the Young’s modulus mismatch between bone (10-30 GPa) and metallic implant materials (e.g.110 GPa for Ti6Al4V). However it remains unclear what external stimuli trigger the most suited biochemical response for allowing not only bone formation but especially its long-term maintenance. Depending on the bone tissue location, bone cells are subjected to different external mechanical stimuli (shear/tension/compression) that trigger different biochemical responses. In addition, bone cells are constantly subjected to intrinsic mechanical stimuli generated by active cell contraction, even in the absence of external stimuli. This project aims to study the influence of mechanical loading on bone cells around endosseous implants, in order to avoid bone loss and implants loosening. Different stress/strain conditions, namely shear, tensile and compression will be applied on mesenchymal stem cells (MSC) cultured on metallic substrates. Different stress/strain conditions will be tested, from replicating current implantation scenarios to novel approaches, to closer-to-physiological (natural bone) ones. For all these cases, MSC proliferation, differentiation into bone cell types and finally these bone cells long term maintenance will be evaluated. After a fundamental study on the preferred stress/strain conditions (type of tension, strain magnitude and frequency), hip and knee implants that convert physiological loading into osteogenic-stimulating stress/strain conditions will be designed. Different architectures (including novel auxetic structures) will be explored for the cross-section of the implant and for the surface of the implant. Additive manufacturing (AM) will be used to manufacture the designed components (for characterization, testing and validation), namely Selective Laser Melting (SLM) due to this technology versatility, allowing a high design freedom once it allows obtaining intricate geometries and small features, joining UN Goal 9 – Industry, innovation and infrastructure, by betting on a cutting-edge technology with the ability to revolutionize the implants industry. After a comprehensive characterization, testing and validation, it is this team aim that Add2MechBio main outcome is fulfilled by having developed effective engineering solutions for hip and knee implants, aiming to reduce their failure and thus contributing to UN Goal 3 – Ensure healthy lives and promote well-being for all at all ages. Covering from mechanobiology to implants design, manufacturing and characterization, Add2MechBio brings together four teams with extremely complementary backgrounds: CMEMS-UMinho with expertise on additive manufacturing fabrication and titanium alloys processing; Aalto University, with large know