Three dimensional printed calcium phosphate and poly(caprolactone) composites with improved mechanical properties and...

Current 3D printed calcium phosphate scaffolds face limitations in mechanical strength and toughness, which are essential for bone tissue engineering. While these scaffolds offer porosity and chemical resorbability, they often fail to meet the mechanical demands of load-bearing applications. Prior research has shown that phosphoric acid binder can generate monetite and hydroxyapatite scaffolds with desired resorbability. However, no prior work had resolved the issue of insufficient mechanical properties in 3D printed calcium phosphate scaffolds. This gap motivated the exploration of sintering and composite formation with poly(caprolactone) (PCL) to enhance scaffold performance. Established knowledge includes the role of porosity in osseointegration, but the integration of PCL into 3D printed scaffolds remains understudied. The need for improved mechanical properties in bone tissue engineering has driven the development of new fabrication techniques. Researchers have proposed that composite materials may offer a solution to mechanical shortcomings. However, the effects of PCL integration on scaffold porosity and integration remain uncertain. This uncertainty drove the investigation into PCL composite formation techniques.

The study aimed to improve the mechanical properties of 3D printed calcium phosphate scaffolds by exploring sintering and composite formation with poly(caprolactone) (PCL). The primary objective was to evaluate how these methods affect scaffold strength, toughness, and porosity. The specific problem addressed is the insufficient mechanical performance of current calcium phosphate scaffolds in load-bearing applications. The motivation stems from the need for scaffolds that can withstand physiological loading while maintaining resorbability. The authors propose that sintering and PCL composite formation may enhance scaffold properties. The study sought to compare two PCL composite formation techniques: postprint precipitation and 3D print codeposition. The goal was to determine which method offers better mechanical improvements without compromising scaffold integration. The investigation also aimed to assess how PCL integration affects surface porosity and its implications for bone regeneration. This approach was chosen to address the limitations of existing 3D printed scaffolds in bone tissue engineering.

The study employed 3D printing of biphasic calcium phosphate powders using phosphoric acid binder to create scaffolds with monetite and hydroxyapatite structures. Sintering was applied to observe changes in scaffold composition and mechanical properties. Two PCL composite formation techniques were tested: postprint precipitation and 3D print codeposition. The scaffolds were analyzed for flexural strength, modulus, and fracture toughness using mechanical testing. Porosity was evaluated using imaging techniques to assess surface and internal structure. The PCL phase continuity was examined to determine its impact on mechanical performance. The effects of sintering on β-TCP evolution and scaffold properties were monitored. The comparison between precipitation and codeposition aimed to identify which method better preserves scaffold porosity while enhancing mechanical properties. The study focused on quantifying mechanical improvements and their trade-offs with porosity preservation.

Sintering of calcium phosphate scaffolds led to the formation of β-TCP and increased flexural strength and modulus but had no effect on fracture toughness. Scaffold porosity increased with sintering, which may improve resorbability but not mechanical performance. PCL composite formation via postprint precipitation and 3D print codeposition significantly improved flexural strength, modulus, and fracture toughness under most conditions. Precipitation yielded greater improvements in mechanical properties compared to codeposition. This was attributed to better continuity of the PCL phase in precipitation-formed composites. However, precipitation also reduced surface porosity due to PCL passivation of the calcium phosphate surface. Codeposition preserved more surface porosity but offered less mechanical enhancement. The study found that PCL integration can augment scaffold properties but may compromise porosity necessary for bone integration. These findings suggest that precipitation is more effective for mechanical improvements but may hinder scaffold integration.

The authors propose that sintering and PCL composite formation can enhance the mechanical properties of 3D printed calcium phosphate scaffolds. Sintering increases flexural strength and modulus but does not improve fracture toughness. PCL composite formation via precipitation offers greater mechanical improvements than codeposition but compromises surface porosity. The study suggests that precipitation is more effective for mechanical augmentation but may hinder scaffold integration. The findings indicate that PCL integration can improve scaffold performance but requires careful consideration of porosity preservation. The authors suggest that the choice of composite formation technique depends on the balance between mechanical enhancement and integration requirements. The results highlight the importance of PCL phase continuity in determining mechanical improvements. The study concludes that precipitation is superior for mechanical properties but may affect bone regeneration potential. These conclusions are based on the observed effects of sintering and PCL integration on scaffold properties.