## 1 Introduction  
Spinal cord injury (SCI), a neurological disorder that disrupts communication within the central nervous system (CNS), can lead to impaired function [1]. The World Health Organization (WHO) reports 250,000-500,000 new cases annually, with the majority (90%) being caused by traumatic lesions to the spinal cord (SC) [2]. The economic burden of SCI in Canadian patients ranges from $1.5 million to $3 million per patient, depending on the type of injury. These lesions can result from car crashes, violence-related wounds, and recreational activities [3]. The type of injury determines the effects on essential bodily functions performed by the motor, sensory, and autonomic systems, which can lead to movement impairment and deficiencies in the somatosensory system [3; 4]. Furthermore, SCI increases the risk of developing diseases, such as multiple sclerosis [5]. Currently, no cure exists for SCI, so treatment methods focus on rehabilitation, reduction of pain and swelling, and pharmacological interventions. [PERSON] et al. reported research on possible pharmacological treatments for different aspects of SCI in 2015. These treatments include Oxcyte, which provides oxygen to the injury site, reducing apoptosis [6]. Furthermore, the inhibition of the nuclear transcription factor, NF-K\(\beta\), may reduce inflammation, and the antibiotic, Minocycline, has shown promising results in decreasing apoptosis in animal models [6]. The steroid, methylprednisolone, was used to treat acute SCI, but the side effects outweighed the benefits and its use has been discontinued [1]. One reason for the lack of effective treatments stems from the fact that the current tools for assessing promising drug targets for treating neurological disorders, like SCI, do not accurately predict toxicity and efficacy. Thus, the field of tissue engineering has been developing new techniques and methodologies that mimic the pathophysiology and functionality of the tissue found in the spinal cord. Tissue engineering uses different combinations of cells, biomaterials, and biochemical factors to produce 3D tissues that resemble human physiology [7]. 3D models offer a significant advantage over 2D models. The 3D environments enable cells to develop into their correct morphology, resulting in more physiologically relevant function [8]. They also offer a microenvironment for encouraging cell-cell and cell-scaffold interactions, similar to how cells would develop normally in vivo [8]. Thus, tissue engineering allows us to study the cell function more precisely in vitro to determine how they would behave under the influence of certain drugs or varying physicochemical conditions. Recent tissue engineering efforts have focused on the use of 3D bioprinting as a novel way to engineer tissues. 3D bioprinting produces 3D structures, often called constructs, using biocompatible materials known as bioinks where encapsulated cells can grow and proliferate [8]. Alternatives to 3D printing include freeze drying, gas foaming, mold casting, electrospinning, and heat compression to create a 3D structure [9]. Nevertheless, most of these methods cannot correctly mimic the necessary microarchitecture for stem cells to differentiate efficiently into neural phenotypes, as some of the aforementioned methods use toxic solvents that affect cell viability and function [9]. In order for the constructs to correctly mimic the SC tissue and serve as a preclinical model of SCI for drug screening applications, specific biological, chemical, and physical conditions must be met [8]. Bioprinting conditions enable the construction of favorable biochemical and mechanical environments, as well as the tunable construction of microstructures, generating an acceptable model to study SCI [9]. Nevertheless, it is important that during the printing protocol, cells remain undamaged. It has been reported that low cell viability can occur due to shear stress acting upon the cells during the printing process [8].