۳D-Printed PCL/Gelatin Membranes for Critical-Size Bone Defect Repair: Role of Pore Size in Bone Formation

Background: Currently, bone lesions and defects are usually treated with surgery and autograft transplantation, which are associated with problems. With the development of tissue engineering knowledge, the method of guided bone regeneration (GBR), which is based on bone growth and prevention of soft and fibrous tissue growth, can replace surgical methods that cause problems. Bioactive molecular scaffolds containing growth factors and antimicrobial agents stimulate and direct osteoblast differentiation and are used in the repair of bone defects. Polycaprolactone (PCL) is a biodegradable synthetic polymer used in tissue engineering. Biocompatibility, bioactivity, and prevention of unwanted cell infiltration are among the advantages of using PCL membranes. The aim of the present study is to investigate the regeneration of adult rabbit calvarium bone using a combination of PCL with biological materials and stimulating factors. Methods: PCL-gelatin membranes were fabricated by ۳D printing in different sizes (۰.۵, ۰.۷۵ and ۱ mm). Osteoblasts, signaling molecules, and growth factors are then loaded into the scaffolds. Four male rabbits (۲۵۰۰-۳۰۰۰ grams) were used for this research under standard conditions. Group ۱: Bone lesions with natural healing process without xenografts, group ۲: Bone lesions with small implant (۰.۵ mm) + bone xenografts (bovine bone), group ۳: Bone lesions with medium implant (۰.۷۵mm) + bone xenografts (bovine bone) and group ۴: Bone lesions with large implant (۱ mm) + bone graft (cow bone). The rabbits were placed under general anesthesia and underwent calvarium surgery. Four defects, each ۸ millimeters in diameter, were created on the calvarium bone and the polycaprolactone membrane and xenograft were implanted. The rabbits were then allowed to recover and heal. After ۱۲ weeks, bone samples were collected from the calvarium and subjected to pathological examination. Hematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) were used for analysis. Results: In group ۱ bone plate was not observed in the middle of the lesion and only natural bone healing occurred at the lesion site. In group ۲, ۳ and ۴ bone septa were observed in the lateral sides and in the middle of the lesion. In other words, in groups with PCL membranes (small-medium-large), new bone formation was approximately the same, although it was slightly greater in the