## 1 Introduction  
In tissue engineering and regenerative medicine, bone repair is still a crucial but difficult area of study. According to [PERSON] [1], bone is a stiff connective structure that facilitates mobility; shields internal organs; and controls blood pH, hematopoiesis, and mineral homeostasis. Collagen and calcium phosphate crystals make up bones; the organic portion of the bone is mainly constituted of collagen, while the inorganic portion is made up of calcium phosphate crystals found in the collagen matrix [2]. Bone is the second most transplanted tissue. Natural regeneration capability is frequently exceeded by severe bone abnormalities brought on by trauma, cancer, osteoporosis, or rheumatoid arthritis [3, 4], which severely reduce patient quality of life and present serious clinical issues [5]. The problem of bone defects can be partially addressed by traditional bone repair techniques like bone grafting [6], which include autologous bone grafting [7] and allogeneic bone grafting [8]. Unfortunately, each of these techniques has drawbacks [9], including poor donor availability, immunological rejection, and discrepancies between material degradation and bone regeneration [10, 11]. For effective and secure defect healing, it is crucial to create the best bone repair scaffolds that replicate the structure and function of natural bone. Bone Tissue Engineering (BTE), which focuses on repairing tissues that have lost their functionality as a result of illness or trauma, can heal bone abnormalities [12, 13]. The utilization of artificial scaffolds (such as bioceramics) as materials for bone tissue healing is currently the main trend in the development of BTE [14, 15]. These scaffolds can assist the growth of new bone by imitating the extracellular matrix (ECM) found in animals. Artificial scaffolds can reduce the risk of infection or immunogenicity, shorten surgical procedures, eliminate the risk of disease transmission, and enable customized scaffold shape and function design based on patient and case characteristics, all of which improve treatment outcomes. It has been shown that bone scaffolds are a great way to address flaws or anomalies in the bone [16]. Since artificial scaffolds are biomaterials that resemble bone, they must be biocompatible, biodegradable, and possess mechanical and thermal properties similar to those of genuine bone [17; 18]. Cell survival and tissue growth are significantly influenced by the structural characteristics of bone tissue repair scaffolds, such as pore size, porosity, geometric shape, and interconnected pore architecture [19; 20]. [PERSON] et al. demonstrated that the distribution of channels or holes encourages fluid flow, whereas interconnected pores help move waste and nutrients. And the form and geometry of interior pores are also structural features that affect bone conduction and mechanical qualities [21]. Pore size affects the adhesion, migration, and proliferation of cells within pores. [PERSON] et al. reported findings across tissue types that Larger pores (e.g., 40-100 \(\upmu\)m) encourage the creation of vascular structures, moderate-sized pores (e.g., 2-12 \(\upmu\)m) support skin migration, and small pores (e.g., 1-2 \(\upmu\)m) aid epidermal cell adhesion for skin regeneration. Multilayer scaffolds in bone tissue engineering that have bigger pores (200-400 \(\upmu\)m) improve vascularization and nutrient diffusion, whereas smaller pores (50-100 \(\upmu\)m) encourage cellular adhesion [20]. Higher porosity increases surface area and spatial availability while keeping the scaffold volume constant. This improves scaffold integration and contact with adjacent tissues, which promotes cell migration, adhesion, and proliferation [22]. A range of 60% to 90% is often ideal for bone tissue repair scaffolds [23; 24; 25], since numerous studies have demonstrated that the choice of porosity is influenced by various parameters, including bone type and scaffold material [26].