## 4 Conclusions  
This study successfully developed and characterized PCL-based fibrous scaffolds reinforced with CNC for potential use in ACL repair. The wet-spinning process, combined with a precise control of parameters such as polymer concentration and flow rate, allowed for the production of uniform and mechanically stable filaments. An automated collector was developed and optimized, which allowed for the stretching of the PCL filaments to \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **T0 (Number of Cells** & **T2 (72 h)** & **Proliferation (\%)** \\  & **24 h After Seeding)** & & \\ \hline S(a) (0 mm) & 10,194 & 18,484 & 81.62 \(\pm\) 29.06 \\ \hline S(b) (2 mm) & 6565 & 11,918 & 81.50 \(\pm\) 12.89 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Proliferation results of BJ-5 ta fibroblasts on the PCL/CNC scaffolds. Figure 7: FESEM images of the cross-section of the structures produced: (**a**) structure S(a) at 250\(\times\) magnification; (**b**) structure S(d) at 80\(\times\) magnification. diameters as low as 30 \(\upmu\)m. The optimized filaments were produced with a 30% (\(w/v\)) PCL concentration and 3% (\(w/v\)) CNC, a flow rate of 6 mL/h, and a 0.61 mm needle diameter. The produced filaments showed an average diameter of 53.57 \(\upmu\)m and demonstrated good mechanical properties, achieving a balance between tensile strength and flexibility (Young's modulus of 0.27 GPa), making it a suitable candidate for tissue engineering applications. The cytotoxicity results indicated that the 30% PCL/3% CNC formulation did not elicit any adverse effects on fibroblast viability, supporting its potential for safe use in biomedical applications. The study also explored the development of braided 3D structures from the optimized filaments, aiming to replicate the fibrous organization of natural ligaments. The use of twisted filament bundles and varying core sizes allowed for the creation of structures with different mechanical and dimensional properties without changing the core integrity of the individual filaments. Proliferation tests demonstrated an 81% success rate, indicating a promising level of cellular compatibility and suggesting that the fabricated structures have significant potential for applications in tissue engineering. The 30% PCL/3% CNC filaments and their derived braided structures show promise as scaffolds for ACL repair. The combination of PCL, a biodegradable and biocompatible polymer, with CNC, a reinforcing agent with similar properties, enables the development of a fully biodegradable system with enhanced mechanical performance. By employing an optimized wet-spinning process and a braiding technique, this approach integrates ultra-thin filaments into 3D structures with superior tensile strength and Young's modulus, closely matching the mechanical properties of native ACL tissue. Future work will focus on refining the production process for 3D structures, particularly improving the uniformity and mechanical performance of larger-diameter scaffolds and conducting in vivo studies to further validate their efficacy for ACL tissue engineering. Conceptualization, D.P.F. ; methodology, J.M.R., R.P.C.L.S., D.S. and S.D.T. ; formal analysis, R.P.C.L.S., S.D.T. and D.P.F. ; investigation, J.M.R., R.P.C.L.S., D.S., S.D.T. and A.R. ; writing--original draft preparation, J.M.R., R.P.C.L.S. and S.D.T. ; writing--review and editing, R.P.C.L.S., S.D.T. and D.P.F. ; supervision, D.P.F. ; project administration, D.P.F. and R.F. ; funding acquisition, D.P.F. and R.F. All authors have read and agreed to the published version of the manuscript.