Understanding in vivo response and mechanical property variation in MgO, SrO and SiO2 doped β-TCP

Abstract

The aim of this work is to evaluate the influence of MgO, SrO and SiO2 doping on mechanical and biological properties of β-tricalcium phosphate (β-TCP) to achieve controlled resorption kinetics of β-TCP system for maxillofacial and spinal fusion application. We prepared dense TCP compacts of four different compositions, i) pure β-TCP, ii) β-TCP with 1.0 wt. % MgO + 1.0 wt. % SrO, iii) β-TCP with 1.0 wt. % SrO + 0.5 wt. % SiO2, and iv) β-TCP with 1.0 wt. % MgO + 1.0 wt. % SrO + 0.5 wt. % SiO2, by uniaxial pressing and sintering at 1250 °C. β phase stability is observed at 1250 °C sintering temperature due to MgO doping in β-TCP. In vitro mineralization in simulated body fluid (SBF) for 16 weeks shows excellent apatite growth on undoped and doped samples. Strength degradation of TCP samples in SBF is significantly influenced by both dopant chemistry and amount of dopant. Compressive strengths for all samples show degradation in SBF over the 16 week time period with varying degradation kinetics. MgO/SrO/SiO2 doped sample shows no strength loss, while undoped TCP shows the maximum strength loss from 419 ±28 MPa to 158 ±28 MPa over the 16 week study. In case of MgO/SrO doped TCP, strength loss is slow and gradual. TCP doped with 1.0 wt. % MgO and 1.0 wt. % SrO shows excellent in vivo biocompatibility when tested in male Sprague-Dawley rats for 16 weeks. Histomorphology analysis reveals that MgO/SrO doped TCP promoted osteogenesis by excellent early stage bone remodeling as compared to undoped TCP.

SrO‐ and MgO‐doped microwave sintered 3D printed tricalcium phosphate scaffolds: Mechanical properties and in vivo osteogenesis in a rabbit model

“…Initiation of osteon formation indicates that osteoid is turning into laminar and osteonic bone. 33,38 Development of osteon formation was observed inside both macro and micro pores as part of the bone modeling and remodeling processes in both pure and dope TCP as shown in Figure 8(a-d). The increased number of osteon and thus haversian canal formation was observed in the newly formed bone in Sr-Mg-doped TCP as compared with pure TCP scaffolds.…”

“…In our previous study with dense TCP, 33 we have shown that the SrO and MgO co-substitution in b-TCP influences the microstructure, density, mechanical strength, and both in vitro and in vivo bioactivity. This study in line of our recent study in a rat cortical defect model 22 demonstrates the beneficial effects of SrO and MgO doping in 3DP interconnected macro porous TCP scaffolds with multiscale porosity.…”

“…Powder preparation was done following our previously published procedure. 33 Briefly, 49 g TCP powder, 0.5 g SrO and 0.5 g MgO (corresponding to 1 wt % SrO and 1 wt % MgO) were mixed in a 250 mL polypropylene Nalgene bottles containing 75 mL anhydrous ethanol and 100 g of 5 mm diameter zirconia milling media. This mixture was milled for 6 h at 70 rpm to minimize agglomerate formation and increase the homogeneity of the powder followed by drying at 60 C for 72 h in an oven.…”

“…[35][36][37] Our previously reported results demonstrated that coexistence of strontium and magnesium in dense TCP scaffolds enhances compressive strength, in vitro degradation kinetics, osteoblast interactions, and in vivo bone formation. 13,33 The purpose of this study was to examine the effect of the coexistence of strontium and magnesium in 3DP interconnected macro porous TCP scaffolds on mechanical strength, and in vivo bone regeneration. The influence of microwave sintering on the compressive strength of these Sr-Mg-doped 3DP TCP scaffolds was evaluated and compared with conventional sintering.…”

Development and characterization of 3CaO·P2O5-SiO2-MgO glass-ceramics with different crystallization degree

“…On the other hand, β-TCMP was present in glass-ceramics based on 3CaO·P 2 O 5 SiO 2 MgO system via crystallization glass bulk [10]. In recent years, the chemical modification of β-TCP through ionic substitutions has received much attention, considering that major components of biological tissues are composed of a calcium phosphate mineral phase containing a variety of other elements [11]. Mg 2+ is considered the most important ion used in calcium substitution in the crystal structure of β-TCP, leading to a change in the biological and chemical behavior of these materials.…”