The presence of highly interconnected three dimensional (3D) pores in the scaffolds are beneficial to promote cell adhesion, mechanical interlocking between host tissue and scaffold via bone ingrowth, and transport of nutrients and metabolic waste ( Ramay and Zhang, 2004 Yang et al., 2002 Sicchieri et al., 2011). It is widely accepted that internal architecture of scaffolds has an important role to play in tissue engineering applications, along with mechanical and biological properties. The bioresorbability of TCP helps it to degrade over time with the ingrowth of host tissues and makes it suitable for many applications. Among other CaPs, tricalcium phosphate (TCP) is one of the most widely used materials due to its bioresorbable property. CaPs offer the advantage of being custom manufactured with respect to the patient and target application based on the CT scan of the defect site ( Hollister, 2005). Calcium phosphate (CaP) bioceramics are widely used in bone-tissue engineering due to their excellent bioactivity, osteoconductivity and compositional similarities to bone ( Bandyopadhyay et al., 2006 Banerjee et al., 2010).
The increasing need for skeletal reconstruction due to bone tumors, trauma, disease, birth defects, and/or war injury demands improved biological and mechanical properties of the existing scaffold materials.
Our results show that bioresorbable 3D printed TCP scaffolds have great potential in tissue engineering applications for bone tissue repair and regeneration. Histomorphological analysis reveals that the presence of both micro and macro pores facilitated osteoid like new bone formation when tested in the femoral defect on Sprague-Dawley rats. An increase in cell density with a decrease in macro pore size is observed during in vitro cell-material interactions using human osteoblast cells. A maximum compressive strength of 10.95 ± 1.28 MPa and 6.62 ± 0.67 MPa is achieved for scaffolds with 500 μm designed pores (~400 μm after sintering) sintered in microwave and conventional furnaces, respectively. A significant increase in compressive strength, between 46% and 69%, is achieved by microwave sintering as compared to conventional sintering as a result of efficient densification. Total open porosity between 42% and 63% is obtained in the sintered scaffolds due to the presence of intrinsic micro pores along with the designed pores. These scaffolds are then sintered at 1150 ☌ and 1250 ☌ in conventional electric muffle furnace as well as microwave furnace.
TCP scaffolds with 27%, 35% and 41% designed macro porosity having pore sizes of 500 μm, 750 μm, and 1000 μm, respectively, have been fabricated via direct 3DP. We report here the fabrication of three dimensional (3D) interconnected macro porous tricalcium phosphate (TCP) scaffolds with controlled internal architecture by direct 3D printing (3DP), and high mechanical strength by microwave sintering.
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