Porous Biodegradable Metals for Hard Tissue Scaffolds: A Review

Abstract

Scaffolds have been utilized in tissue regeneration to facilitate the formation and maturation of new tissues or organs where a balance between temporary mechanical support and mass transport (degradation and cell growth) is ideally achieved. Polymers have been widely chosen as tissue scaffolding material having a good combination of biodegradability, biocompatibility, and porous structure. Metals that can degrade in physiological environment, namely, biodegradable metals, are proposed as potential materials for hard tissue scaffolding where biodegradable polymers are often considered as having poor mechanical properties. Biodegradable metal scaffolds have showed interesting mechanical property that was close to that of human bone with tailored degradation behaviour. The current promising fabrication technique for making scaffolds, such as computation-aided solid free-form method, can be easily applied to metals. With further optimization in topologically ordered porosity design exploiting material property and fabrication technique, porous biodegradable metals could be the potential materials for making hard tissue scaffolds.

Porous magnesium-based scaffolds for tissue engineering

“…4 provide a scaffold for the bone tissue to grow into and through the pores thus making a suitable bond to the metallic implant [8]. Present tissue engineering approaches are focused on the development of porous scaffolds made of different biomaterials with the aim of replacing and restoring the pathologically altered tissues by transplantation of the cells [9,10].…”

“…The treatment of large bone segments caused by tumors, trauma, implant failure, or osteitis is far more challenging to be addressed. An ideal bone tissue engineering scaffold must be biocompatible, osteoconductive, and biodegradable, with a high mechanical strength to fulfil the necessary loadbearing functions [8]. Also, it must have interconnected porous networks allowing cell migration, vascularization and nutrient delivery [16].…”

Comparative mechanical and corrosion studies on magnesium, zinc and iron alloys as biodegradable metals

“…[4][5][6][7][8][9][10] Iron is also an essential element for proper biological functions, mainly for the transfer of oxygen by blood. 13 The recommended daily value of Fe is about 10 mg. 6 Regarding the biocompatibility of iron-based alloys, there are a number of reported results, [14][15][16] but they are often controversial. In order to explain the discrepancies between biocompatibility tests, more in-vitro and in-vivo experiments are needed.…”

“…Appropriate alloying of Mg, Zn and Fe can positively modify their mechanical, corrosion and physical properties, which are important for potential medical applications. In the available literature many alloying elements are proposed for these purposes, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] but in this study Mg-RE (RE = rare earth metals, Gd, Nd, Y), Zn-Mg and Fe-Mn based alloys were selected, because all these alloying systems are generally considered as relatively safe and acceptable for a potential medical use. 3 …”

Current Status and Recent Developments in Porous Magnesium Fabrication

“…Alloying additives included calcium, zinc, and aluminum. [74] The Ca addition in MZX211, for example, apparently accelerates alloy dissolution and aluminum in the AZ63 alloy slows it down. [36] If porous magnesium is in the human body and adequate ions (calcium and phosphate) are present, a complex bioactive deposition layer could be formed on the magnesium surface.…”