Micro-/Nano-Structured Ceramic Scaffolds That Mimic Natural Cancellous Bone

Natural cancellous bone features a complex micro- and nano-architecture that supports cell adhesion and tissue regeneration. While synthetic scaffolds have been developed to mimic bone, few studies have simultaneously addressed structural similarity, mechanical properties, and biological compatibility. Prior research has shown that α-tricalcium phosphate (α-TCP) and silicocarnotite (SC) are promising materials for bone scaffolds. However, no prior work had resolved how to control surface nanostructure and mechanical strength while ensuring non-cytotoxicity and functionalization with biomolecules. This gap motivated the development of a scaffold that replicates both the structural and compositional features of cancellous bone. Researchers have explored various fabrication techniques, but the polymer replica method remains underutilized for bone-like scaffolds. The absence of a scaffold that integrates structural, mechanical, and biological properties limits progress in bone tissue engineering. This uncertainty drove the investigation into a composite scaffold with a defined composition and controlled cooling rates. The need for a scaffold that supports cell proliferation and extracellular matrix formation remains unmet in current literature.

This study aimed to develop a composite scaffold that mimics the micro- and nano-structure of natural cancellous bone. The goal was to create a material with a defined composition of α-TCP and SC, fabricated using the polymer replica method. The objective was to control surface nanostructure and mechanical strength by varying cooling rates. Researchers also wanted to evaluate the scaffold's non-cytotoxicity and its ability to support cell proliferation. A secondary aim was to functionalize the scaffold with alkaline phosphatase (ALP) to enhance biological activity. The motivation was to produce a scaffold that integrates structural, mechanical, and biological features. The researchers proposed that such a scaffold could improve bone regeneration outcomes. This approach addresses the limitations of current scaffolds by incorporating multiple design parameters.

The composite scaffolds were synthesized using the polymer replica method with a fixed composition of 46.6% α-TCP and 53.4% SC. Three cooling rates (50, 16.5, and 5.5 °C/h) were applied to control surface nanostructure and mechanical strength. Scanning electron microscopy (SEM) was used to compare scaffold morphology with natural cancellous bone. Transmission electron microscopy (TEM) and Raman analysis characterized the surface nanostructures. The scaffold phases were confirmed to be compact and dense without porosities or cracks. In vitro non-cytotoxicity was assessed by culturing adult human mesenchymal stem cells (ah-MSCs) on scaffold surfaces. Cell proliferation was monitored over time to evaluate cytotoxicity. Finally, the scaffolds were functionalized with alkaline phosphatase (ALP) to test biological activity.

The scaffolds exhibited a micro- and nano-structure similar to natural cancellous bone. The SEM analysis confirmed structural similarity and the absence of porosities or cracks. TEM and Raman analysis revealed well-defined surface nanostructures. The scaffolds were composed of compact and dense α-TCP and SC phases. In vitro tests showed no cytotoxicity, with cell proliferation increasing over 28 days. A dense cell-hydroxyapatite layer formed by day 28. SEM analysis suggested extracellular matrix formation mediated by cells. ALP was successfully grafted onto the scaffolds, maintaining enzymatic activity. These findings indicate that the scaffolds support both structural and biological functions. The controlled cooling rates allowed for precise mechanical and surface property tuning. The composite material demonstrated compatibility with cell growth and matrix formation. The functionalization with ALP enhanced the scaffold's biological activity.

The study demonstrated that micro-/nano-structured scaffolds can mimic the architecture and composition of natural cancellous bone. The polymer replica method enabled the synthesis of a composite with controlled surface and mechanical properties. The scaffolds supported cell proliferation and extracellular matrix formation without cytotoxicity. The absence of porosities and cracks suggests structural integrity. The successful grafting of ALP indicates potential for biological functionalization. The cooling rate influenced surface nanostructure and mechanical strength. The researchers proposed that these scaffolds could serve as a model for bone tissue engineering. The findings suggest that structural and compositional similarity supports biological activity.