Magnesium-based alloys with adapted interfaces for bone implants and tissue engineering

Magnesium and its alloys are one of the most used materials for bone implants and tissue engineering.They are characterized by numerous advantages such as biodegradability,high biocompatibility and mechanical properties with values close to the human bone.Unfortunately,the implant surface must be adequately tuned,or Mg-based alloys must be alloyed with other chemical elements due to their increased corrosion effect in physiological media.This article reviews the clinical challenges related to bone repair and regeneration,classifying bone defects and presenting some of the most used and modern therapies for bone injuries,such as Ilizarov or Masquelet techniques or stem cell treatments.The implant interface challenges are related to new bone formation and fracture healing,implant degradation and hydrogen release.A detailed analysis of mechanical properties during implant degradation is extensively described based on different literature studies that included in vitro and in vivo tests correlated with material properties’characterization.Mg-based trauma implants such as plates and screws,intramedullary nails,Herbert screws,spine cages,rings for joint treatment and regenerative scaffolds are presented,taking into consideration their manufacturing technology,the implant geometrical dimensions and shape,the type of in vivo or in vitro studies and fracture localization.Modern technologies that modify or adapt the Mg-based implant interfaces are described by presenting the main surface microstructural modifications,physical deposition and chemical conversion coatings.The last part of the article provides some recommendations from a translational perspective,identifies the challenges associated with Mg-based implants and presents some future opportunities.This review outlines the available literature on trauma and regenerative bone implants and describes the main techniques used to control the alloy corrosion rate and the cellular environment of the implant.

In vitro characterization of novel nanostructured collagen-hydroxyapatite composite scaffolds doped with magnesium with improved biodegradation rate for hard tissue regeneration

New materials are required for bone healing in regenerative medicine able to temporarily substitute damaged bone and to be subsequently resorbed and replaced by endogenous tissues.Taking inspiration from basic composition of the mammalian bones,composed of collagen,apatite and a number of substitution ions,among them magnesium(Mg2+),in this work,novel composite scaffolds composed of collagen(10%)-hydroxyapatite(HAp)(90%)and collagen(10%)-HAp(80%)-Mg(10%)were developed.The lyophilization was used for composites preparation.An insight into the nanostructural nature of the developed scaffolds was performed by Scanning Electron Microscopy coupled with Energy Dispersive X-Ray and Transmission Electron Microscopy coupled with Energy Dispersive X-Ray.The HAp nanocrystallite clusters and Mg nanoparticles were homogeneously distributed within the scaffolds and adherent to the collagen fibrils.The samples were tested for degradation in Simulated Body Fluid(SBF)solution by soaking for up to 28 days.The release of Mg from collagen(10%)-HAp(80%)-Mg(10%)composite during the period of up to 21 days was attested,this composite being characterized by a decreased degradation rate with respect to the composite without Mg.The developed composite materials are promising for applications as bone substitute materials favouring bone healing and regeneration.