Long-Term Examination of Degradation and In Vivo Biocompatibility of Some Mg-0.5Ca-xY Alloys in Sprague Dawley Rats

Abstract

The medical field has undergone constant development in recent years, and a segment of this development is occupied by biodegradable alloys. The most common alloys in this field are those based on Mg, their main advantage being the ability to degrade gradually, without affecting the patient, and also their ability to be fully absorbed by the human body. One of their most important conditions is the regeneration and replacement of human tissue. Tissue can be engineered in different ways, one being tissue regeneration in vivo, which can serve as a template. In vivo remodeling aims to restore tissue or organs. The key processes of tissue formation and maturation are: proliferation (sorting and differentiation of cells), proliferation and organization of the extracellular matrix, biodegradation of the scaffold-remodeling, and potential tissue growth. In the present paper, the design of the alloys in the Mg-Ca-Y system is formed from the beginning using high-purity components, Mg-98.5%, master-alloys: Mg-Y (70 wt.%-30 wt.%) and Mg-Ca (85 wt.%-15 wt.%). After 8 weeks of implantation, the degradation of the implanted material is observed, and only small remaining fragments are found. At the site of implantation, no inflammatory reaction is observed, but it is observed that the process of integration and reabsorption, over time, accentuates the prosaic surface of the material. The aim of the work is to test the biocompatibility of magnesium-based alloys on laboratory rats in order to use these alloys in medical applications. The innovative parts of these analyses are the chemical composition of the alloys used and the tests performed on laboratory animals.

Keywords: Mg-Ca-Y biodegradable alloys; in vivo animal study; surface morphology.

Figure 1

Surgical procedure used to implant metallic samples: (a)—preoperative aspect; (b)—the incision of the skin and the exposure of the femur; (c)—fixing the piece next the femur; (d)—skin suture; (e)—fixing the piece in the lumbar area; (f)—post-operatory appearance.

Figure 2

Rats, post-operative representative radiographs, Mg-0.5Ca-xY alloy (red arrows) and air sacs, dorsal–ventral (a,c,e) and lateral–lateral (b,d,f) lying. After 2 weeks (a,b), 4 weeks (c,d), and 8 weeks (e,f).

Figure 3

Rat, post-operative representative CT images, Mg-0.5Ca-xY alloy and gas inclusions, lumbar spine (a,c,e,g) and femur (b,d,f) regions. After 1 week (a,b), 2 weeks (c,d), 4 weeks (e,f), and 8 weeks (g,h).

Figure 4

Rat tissue, representative results of histological examination, MTC staining, 1 week later (a–c), 2 weeks (d–f), 4 weeks (g–i), and 8 weeks (j–l). Mg-0.5Ca-xY alloy (red arrow), gas inclusions (green arrow), fibroblast collagen fibers (yellow arrow), and neovascularization (black arrow).

Figure 5

SEM images taken of rats after one week in (a) at magnification of 2000×; (b) at magnification of 5000×.

Figure 6

SEM images of rats after two weeks (a) at magnification of 2000×; (b) at magnification of 5000×.

Figure 7

SEM images of rats after four weeks for Mg-0.5Ca-1.5Y (a) at magnification of 500×; (b) at magnification of 5000×.

Figure 8

SEM images of rats after four weeks for Mg-0.5Ca-1.5Y (a) at magnification of 1000×; (b) at magnification of 5000×.

Figure 9

SEM images of rats after eight weeks (a) at magnification of 2000×; (b) at magnification of 5000×.