3D printed tricalcium phosphate bone tissue engineering scaffolds: effect of SrO and MgO doping on in vivo osteogenesis in a rat distal femoral defect model

Abstract

The presence of interconnected macro pores is important in tissue engineering scaffolds for guided tissue regeneration. This study reports in vivo biological performance of interconnected macro porous tricalcium phosphate (TCP) scaffolds due to the addition of SrO and MgO as dopants in TCP. We have used direct three dimensional printing (3DP) technology for scaffold fabrication followed by microwave sintering. Mechanical strength was evaluated by scaffolds with 500 µm, 750 µm, and 1000 µm interconnected designed pore sizes. Maximum compressive strength of 12.01 ± 1.56 MPa was achieved for 500 µm interconnected designed pore size Sr-Mg doped scaffold. In vivo biological performance of the microwave sintered pure TCP and Sr-Mg doped TCP scaffolds was assessed by implanting 350 µm designed interconnected macro porous scaffolds in rat distal femoral defect. Sintered pore size of these 3D printed scaffolds were 311 ± 5.9 µm and 245 ± 7.5 µm for pure and SrO-MgO doped TCP scaffolds, respectively. These 3D printed scaffolds possessed multiscale porosity, i.e., 3D interconnected designed macro pores along with intrinsic micro pores. Histomorphology and histomorphometric analysis revealed a significant increase in osteoid like new bone formation, and accelerated mineralization inside SrO and MgO doped 3D printed TCP scaffolds as compared to pure TCP scaffolds. An increase in osteocalcin and type I collagen level was also observed in rat blood serum with SrO and MgO doped TCP scaffolds compared to pure TCP scaffolds. Our results show that these 3D printed SrO and MgO doped TCP scaffolds with multiscale porosity contributed to early healing through accelerated osteogenesis.

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

“…The presence of micro pores in the scaffold strut/wall is an integral part of the 3DP because of the absence of dense sintering (i.e., no pressure, uniaxial or isostatic, was applied to compact the samples at any stage of the process). 8,22 The presence of multiscale porosity and 3D interconnected microenvironment in tissue engineering scaffolds increases the overall performance by increased osteoconduction and osseointegration. 22,[40][41][42] Addition of dopants in b-TCP influences its phase stability, microstructure, grain size, mechanical strength, and strength degradation kinetics.…”

“…8,22 The presence of multiscale porosity and 3D interconnected microenvironment in tissue engineering scaffolds increases the overall performance by increased osteoconduction and osseointegration. 22,[40][41][42] Addition of dopants in b-TCP influences its phase stability, microstructure, grain size, mechanical strength, and strength degradation kinetics. Irrespective of the sintering method, addition of SrO and MgO dopants in TCP resulted in smaller grain size.…”

“…CaP scaffolds fabrication with complex geometrical features is very challenging by conventional techniques since precise controlling of pore size, interconnectivity, distribution, and volume fraction porosity cannot be done. 8,[21][22][23] We have recently reported successful direct 3D printing (3DP) of three dimensionally interconnected porous TCP scaffolds with different pore size and volume fraction porosity. 8,23,24 Both pure 8 and doped 23,24 3DP TCP scaffolds showed higher compressive strength compared with scaffolds produced via other solid freeform fabrication (SFF) techniques.…”

Rapid prototyping technology and its application in bone tissue engineering

“…Furthermore, because the processes are performed at room temperature, heat-sensitive biologically active factors can be added during printing (Chia and Wu, 2015). However, the final products usually have weak biomechanical strength, which require high-temperature sintering to obtain structures suitable for bone tissue engineering (Seitz et al, 2005;Lu et al, 2012;Tarafder et al, 2013;Tarafder and Bose, 2014;Qian et al, 2015). Exploration of better binders is currently underway (Inzana et al, 2014).…”

Bioceramic Scaffolds

“…One of the important benefits of this method is the powder bed support by itself for each successive layer. The fragility of the obtained parts is considered a drawback [81][82][83][84][85][86][87][88].…”