## 1 Introduction
In terms of biodegradability, it should degrade at a controlled rate to provide structural support throughout the healing process while gradually being replaced by regenerated tissue. Polycaprolactone (PCL) has been identified as one of the most promising synthetic polymers for tissue engineering applications, especially for long-term use, due to its slow degradation rate, high mechanical strength, and ease of processing [15; 16; 17]. PCL's ability to maintain mechanical stability over extended periods makes it particularly well-suited for applications where prolonged support is necessary, such as in ACL repair, where regeneration and full functionality can take up to 4 months [18]. Additionally, PCL can be combined with other materials or bioactive agents to further enhance its biological properties and facilitate tissue integration. [PERSON] et al. investigated PCL-based scaffolds and found that adding hydroxyapatite (HAp) particles enhanced cell proliferation and promoted an osteogenic phenotype in human adipose-derived stem cells [19]. The study also showed that varying filament diameter by adjusting extraction speed significantly improved the mechanical properties, with higher speeds yielding better performance. Similarly, [PERSON] et al. assessed the synthesis of PCL fibers produced by electrospinning, highlighting the material's capacity for cell adhesion and proliferation, although the mechanical properties of the electrospun PCL filaments were somewhat weaker compared to native ACL tissue [20]. These studies underscore the versatility of PCL and its ability to be customized to meet the specific mechanical and biological requirements of ligament repair. In addition to PCL, cellulose nanocrystals (CNC) have attracted considerable interest as reinforcing agents in polymeric systems due to their high surface area, excellent mechanical properties, and biodegradability [21; 22]. CNC, derived from renewable resources, offers a sustainable option for enhancing the mechanical strength of polymer scaffolds without compromising their biocompatibility [6; 23; 24; 25]. CNC has been shown to improve the tensile strength, elasticity, and structural stability of polymeric scaffolds, making them ideal for load-bearing applications such as ligament repair. [PERSON] et al. conducted a notable study where CNC was incorporated into sodium alginate fibers using a wet-spinning process, resulting in significant improvements in tensile strength and elongation at the break of the filaments [26]. The integration of CNC into PCL scaffolds represents a promising strategy to develop structures with enhanced mechanical properties while maintaining biocompatibility [27; 28]. CNC has been widely used as a substance conducive to obtaining filaments with dimensions on the micrometer scale and improved mechanical properties [26; 29; 30; 31]. [PERSON] et al. emphasized that the wet-spinning technique, despite its limitations in producing filaments primarily at the microscale, offers several advantages, including the ability to control filament orientation and scaffold architecture, which are critical for mimicking the mechanical behavior of ligaments and tendons [32]. Such precise control is vital to replicating the hierarchical organization of native tissues, where filament alignment plays a key role in load distribution and tensile strength. Furthermore, textile engineering techniques provide the tools necessary to produce filament-based structures that mimic the extracellular matrix (ECM) and promote cell growth and tissue regeneration [33; 34; 35]. Braided and woven structures, for instance, have been successfully used to develop ACL scaffolds with mechanical properties comparable to native tissue [36]. These techniques allow for the production of scaffolds with tunable mechanical properties, controlled porosity, and optimal filament orientation, facilitating cell proliferation and migration. The scaffolds produced by these techniques show enhanced mechanical properties by improving load distribution and resistance to deformation.