## 1 Introduction  
The nervous system is vital in the human body and is made from two distinct components, the central nervous system (CNS) and the peripheral nervous system (PNS). Both parts are potentially subjected to various acute and chronic diseases and injuries, causing reduced quality of life [1; 2; 3]. In the case of peripheral nerve injuries, mechanical stress; exposure to heat, cold, and irradiation; tumors; and focal inflammation are the main reasons for partial or total loss of motor, sensory, and autonomic functions [4]. For example, cutting of the nerve as a result of traumatic injuries may result in complications like inability to move muscles, dysfunctional or no feeling of normal sensations, and eventually painful neuropathies [5]. To date, huge numbers of experimental studies have been conducted to provide appropriate substitutes for the reconstruction of lost/injured peripheral nerves. Autografts, mostly harvested from the sural nerve, are still identified as the gold standard for the regeneration of nerves as regards lack of rejection and providing a proper biological environment for axon reconstruction [6]. Another approach for restoring segmental nerve injuries involves the use of allografts, which depends on the viability of host and donor Schwann cells since they are responsible for the proper re-myelination process and serve as the main source for neurotrophic factors [7; 8; 9]. In the era of tissue engineering and regenerative medicine, the use of natural and synthetic biopolymers offers notable opportunities in neuroregeneration approaches [10; 11; 12]. Furthermore, scientists are steadily applying engineering approaches for the modification and improvement of polymeric tissue substitutes to accelerate neural tissue repair and regeneration. In this context, the use of bioactive glasses (BGs) for neural tissue engineering is emerging as an innovative strategy. BGs have been conventionally applied for the repair and regeneration of osseous tissue in orthopedic and dental applications due to their capability of forming a chemical bond with living bone [13]. This unique property relies on an ion-exchange mechanism between glass and biological fluids, leading to the formation of an interfacial layer of nano-hydroxyapatite. The fundamentals of BG processing, properties, and applications in contact with bone have been comprehensively reviewed elsewhere [14; 15; 16]. Furthermore, it can be stated that there is a consensus among the experts in the field on the suitability of BGs for soft tissue engineering applications, too. Several studies have shown and summarized the use of different types of glasses in the management of soft-tissue-related damage and injuries [17; 18]. Peripheral nerve and spinal cord regeneration have also been amongst the targets of BG-based therapies [19]. Many relevant studies have proposed the use of silicate-based BGs for nerve regeneration [20; 21]; however, these materials often suffer from mechanical fragility and brittleness and, even more importantly, lack of degradability in biological environments, which hinders their application as effective tissue-engineered implantable temporary device [22]. Therefore, other types of BGs, i.e., phosphate- and borate-based glasses, were applied as alternatives in neuroregeneration strategies to overcome the limitations of silicate-based BGs [23; 24]. In this regard, glasses in different shapes (particles and fibers) were added to polymeric matrixes to fabricate three-dimensional (3D) composite scaffolds which are flexible substitutes for neural tissue engineering [24; 25]. Despite the promising early results, there are many substantial questions that should be addressed before the extensive usage of BGs, including the toxicity of BG by-products in the defect sites. Furthermore, tuning the degradation time of BGs should be carefully assessed as it may affect the final clinical outcome.