Enhancement of Osteogenesis and Biodegradation Control by Brushite Coating on Mg–Nd–Zn–Zr Alloy for Mandibular Bone Repair

Abstract

To diminish incongruity between bone regeneration and biodegradation of implant magnesium alloy applied for mandibular bone repair, a brushite coating was deposited on a matrix of a Mg-Nd-Zn-Zr (hereafter, denoted as JDBM) alloy to control the degradation rate of the implant and enhance osteogenesis of the mandible bone. Both in vitro and in vivo evaluations were carried out in the present work. Viability and adhesion assays of rabbit bone marrow mesenchyal stem cells (rBM-MSCs) were applied to determine the biocompatibility of a brushite-coated JDBM alloy. Osteogenic gene expression was characterized by quantitative real-time polymerase chain reaction (RT-PCR). Brushite-coated JDBM screws were implanted into mandible bones of rabbits for 1, 4, and 7 months, respectively, using 316L stainless steel screws as a control group. In vivo biodegradation rate was determined by synchrotron radiation X-ray microtomography, and osteogenesis was observed and evaluated using Van Gieson's picric acid-fuchsin. Both the naked JDBM and brushite-coated JDBM samples revealed adequate biosafety and biocompatibility as bone repair substitutes. In vitro results showed that brushite-coated JDBM considerably induced osteogenic differentiation of rBM-MSCs. And in vivo experiments indicated that brushite-coated JDBM screws presented advantages in osteoconductivity and osteogenesis of mandible bone of rabbits. Degradation rate was suppressed at a lower level at the initial stage of implantation when new bone tissue formed. Brushite, which can enhance oeteogenesis and partly control the degradation rate of an implant, is an appropriate coating for JDBM alloys used for mandibular repair. The Mg-Nd-Zn-Zr alloy with brushite coating possesses great potential for clinical applications for mandibular repair.

Radiological, histological, and hematological evaluation of hydroxyapatite‐coated resorbable magnesium alloy screws placed in rabbit tibia

“…In our experiment, coating the screw surfaces with HA was used to control resorption and enhance biocompatibility. HA is well known for its excellent biocompatibility . In previous study, we could also confirm the cell affinity with HA coating in vitro test .…”

Influence of The KF Concentration on The Coating Process And Properties of Potentiostatic Deposited Fluoride Conversion Film on AZ31 Mg Alloy

“…Figure 8a presents that the molar percent ratio of MgF 2 to Mg(OH) 2 in the outside part is close to a constant, which may be caused by the stable conversion process that executes an equilibrium reaction by formula (1). In 0.1 M~0.5 M KF solutions, the FCF layers shown in Figure 8b- In sum, the potentiostatic deposition process of the conversion film on AZ31 Mg alloy in 0.05 M KF solution executes an equilibrium conversion as described in formula (1), and the molar percent ratio of MgF 2 to Mg(OH) 2 is close to a constant as shown in Figure 8a. While in 0.1 M and 0.2 M KF solutions, the crystallization process of KMgF 3 may execute the reaction of MgF 2 combining with KF as shown in formula (2).…”

“…Magnesium (Mg) and its alloy have closer density and elastic modulus (density: 1.7-2.04 g/cm -3 , Young's modulus: 41-45 GPa) to those of natural bone (density: 1.8-2.1 g/cm -3 , Young's modulus: 10-30 GPa) than traditional implants such as 316L stainless steels, Ti6Al4V alloys, Co-Cr based alloys, thus when implanted they can minimize the stress shielding effect that can cause delay in healing process of damaged bones and implant loosening [1][2][3] . Additionally, Mg can be excreted in terms of soluble MgCl 2 through urine, and Mg is considered as a beneficial element in maintaining the normal function of the human metabolism and the growth of new bone tissue [2,3] .…”

“…Additionally, Mg can be excreted in terms of soluble MgCl 2 through urine, and Mg is considered as a beneficial element in maintaining the normal function of the human metabolism and the growth of new bone tissue [2,3] . Moreover, Mg can totally degrade in the physiological system (pH 7.4-7.6), thus eliminating the need for secondary surgery [1][2][3][4][5] . These intriguing characteristics make Mg and its alloys have great potential in orthopaedic application.…”

Self-healing property of hydroxyapatite and octacalcium phosphate coatings on pure magnesium and magnesium alloy

“…A brushite (dicalcium phosphate dihydrate) coating prolonged the in vivo degradation period of a Mg-Nd-Zn-Zr alloy [21]. The brushite coating thinned as mature bone tissue formed around the alloy screws in the mandibles of rabbits, after reducing the initial degradation rate [22]. New bone ingrowth around Mg alloys appeared to be enhanced when the coating of a Mg alloy was a degradable calcium phosphate such as -tricalcium phosphate (-TCP) [23].…”