## 1 Introduction  
Bone tissue has the natural ability to self-degenerate after minor traumas or fractures. However, this regenerative capacity is no longer sufficient in the case of large bone defects, often caused by degenerative diseases, severe injuries, or tumors. In such cases, surgical interventions are required to restore the full functionality of the bone [1]. Biomaterials offer innovative solutions for bone and tissue regeneration. These materials, designed to mimic the mechanical and biological properties of tissues, can be implanted in the defect areas to support their growth and regeneration [2]. A wide range of biomaterials are available in the scientific literature, including natural and synthetic polymers, metal oxides, and bioceramics, offering versatile solutions for tissue regeneration [3]. Each biomaterial provides unique characteristics that can be customized to specific tissue engineering needs, paving the way for innovative approaches in regenerative medicine [4]. Indeed, tissue can react to implants with various types of local reactions. The course and effectiveness of implant penetration depend on the structure and shape of the implant. Metal oxides such as titanium alloys have high mechanical strength and do not easily deform or degrade, unlike many of the natural polymers used, which have a short lifespan and are more often used for implants for soft tissue treatment [3]. On the other hand,metals oxides like titanium are not corrosion-resistant and bond with bone, meaning that the addition of surface coatings is often necessary to increase their bioactivity and corrosion resistance [5]. In this scenario, the choice of bioceramics for treating bone defects provides a good compromise between biocompatibility, biodegradability, strength, osteoconductivity, and osteoinduction. The high hardness and good resistance to abrasion and corrosion in tissue and body fluid environments minimize the wear of ceramic biomaterials after long-term use [6]. Specifically, among these solutions, silica-based bio-glasses can be used for efficient applications in bone tissue engineering as they can enhance revascularization, osteoblast adhesion, enzymatic activity, and the differentiation of mesenchymal stem cells, since they are capable of forming a biologically active hydroxycarbonate apatite layer which is chemically and structurally very similar to the mineral phase of bone and provides an interface that binds to tissues [7]. Silica-based bio-glasses synthesized through the sol-gel method represent a valuable choice for applications in tissue engineering, especially for tissue regeneration post-implantation. The intrinsic ability of the sol-gel method to create porous structures allows for the increased flow of liquids and nutrients through the implanted material, thereby enhancing the adhesion and proliferation of mesenchymal cells. Moreover, the possibility of incorporating bioactive molecules, metabolites, and growth factors into the bio-glass further accelerates the healing process and helps to mitigate the risk of infections and post-implantation inflammation [8; 9; 10]. These loaded systems avoid implant rejections through a controlled drug release at the implantation site [11]. Indeed, the sol-gel technique, which concerns a transition from a solution (sol) into a solid matric (gel) through hydrolysis and polycondensation reactions, enables the precise control of the composition and structure of the biomaterials, allowing the development of hybrid bio-glasses with targeted properties [12; 13; 14]. This technique, operating at relatively low temperatures, helps to preserve the bioactivity of the incorporated organic molecules, which can further enhance the regenerative process or prevent inflammatory events or bacterial infection [13; 15; 16].