Abstract
Surface-mineralized collagen sponges have attracted much attention as scaffolds for bone tissue engineering. Recently, we developed amorphous calcium phosphate (ACP) and low-crystalline apatite coating processes on collagen sponges. In the present study, we applied these coating processes to granular collagen sponges (referred to as Col) to compare the bone tissue regeneration capabilities of ACP-coated and apatite-coated Col (referred to as Col-ACP and Col-Ap, respectively) using a rat cranial bone defect model. According to micro-CT and histological analyses, Col-Ap enhanced bone tissue regeneration compared to Col, whereas Col-ACP did not. These results not only demonstrated the superior bone tissue regeneration capability of Col-Ap, but also indicated limitations of the in vitro simulated body fluid (SBF) test used in our previous study. Despite the apatite-forming ability of Col-ACP in SBF, it was ineffective in improving bone tissue regeneration in vivo, unlike Col-Ap, most likely due to the quick resorption of the ACP coating in the defect site. The present results clarified the importance of the coating stability in vivo and revealed that the low-crystalline apatite coating was more beneficial than the ACP coating in the fabrication of surface-mineralized collagen sponges for use as bone tissue engineering scaffolds.
Highlights
Biodegradable scaffolds with a three-dimensional (3D) porous structure play an important role in bone tissue engineering
Biocompatible and bioresorbable collagen sponges coated with low-crystalline apatite have attracted attention as scaffolds for bone tissue engineering owing to their similarity to human bone
As shown in the scanning electron microscope (SEM) images (Figure 1a), spherical nanoparticles and a nanostructured layer appeared on the Col-amorphous calcium phosphate (ACP) and Col-Ap surfaces, respectively
Summary
Biodegradable scaffolds with a three-dimensional (3D) porous structure play an important role in bone tissue engineering. They support cell adhesion, growth, and osteogenic differentiation; facilitate the formation of blood vessels; and resorb while being replaced with the newly formed bone. Collagen fibrils mineralized with nonstoichiometric low-crystalline apatite constitute the basic building blocks [1]. Biocompatible and bioresorbable collagen sponges coated with low-crystalline apatite have attracted attention as scaffolds for bone tissue engineering owing to their similarity to human bone. A non-crystalline phase of calcium phosphate is concentrated within the intracellular vesicles of osteoblasts [8,9], and later, infiltrates the collagen fibrils where it crystallizes to form low-crystalline apatite [10,11]
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