## 4 Discussion
Isopropanol was used as the main regeneration and washing solvents since its low surface tension (0.023 N/m) tends to decrease the number of closed pores during supercritical drying; besides, in previous studies, it has been proven the CAs regenerated in iPOH have higher mechanical properties than other forms of alcohols (e.g., EtOH) [3; 30]. BJH desorption results also showed that F\({}_{\text{s}}\) had significantly higher pore volume (1.03 cm\({}^{3}\)/g) than F\({}_{\text{c}}\) (0.36 cm\({}^{3}\)/g). The obtained value for F\({}_{\text{c}}\) was lower compared to the porosity acquired by \(\mu\)-CT because of the resolution limitation of the \(\mu\)-CT technique which will be discussed further. Overall, both fibers have mainly mesoporous structure with fewmacroscale pores. Based on the results of the aforementioned methods, F\({}_{8}\) originated from the high molecular weight with lower crystallinity cellulose (C\({}_{8}\)) led to thinner nanofibrillar formation (SEM, BET/BJH), interconnected pore structure (\(\upmu\)-CT), and higher surface area and pore volume (BET/BJH). The difference in the results needs to be explained by understanding the sample preparation and measurement basis of each technique. SEM image analysis is limited to 2D and is highly dependent on the settings used during binary image production. Inaccuracy might also arise from the fibers cross-section preparation since even cutting in liquid N\({}_{2}\) can deform the nanofibrillars. Additionally, fibrils are highly sensitive to the electron beam and throughout the imaging process they can form clusters upon applying high voltages (2-5 kV) [54]. In addition, although the \(\upmu\)-CT analyses provide a more in-depth and accurate overview of 3D structures with insight into the closed pores, the resolution of this technique is limited (in this study, 0.8 \(\upmu\)m); this can cause errors, such as neglecting nanofibrils, or considering the agglomeration in the fiber matrix, it might fail to obtain a precise internal computed construction. On the other hand, N\({}_{2}\) adsorption and desorption data based on BET and BJH theory report the pores which are accessible for gas; miscalculations might arise due to nanofibrillar structural changes in the N\({}_{2}\) pressure variation during the measurements causing some errors in pore diameter values [47; 53]. In the case of microfiber shapes, this error can be even higher due to brittleness, high electrostatic charges, and the very lightweight nature of samples. After all, to add enough mass of the fibers in the bulb of the test tube, the aerogel fibers might have been compressed by transferring the samples into the bottom of the tube. It is challenging to control the applied compression when the ultralight aerogel microfibers samples were filled in the test tube. More advanced characterization methods, such as nano-CT as a super high-resolution imaging techniques, are required to obtain a better understanding of the textural properties of CA fibers [55]. The difference in the cell proliferation of the powders might arise from their purity. Regarding the CA fibers, the slower cell proliferation in the F\({}_{8}\) can be due to minor trapped salt molecules, which can be thoroughly investigated by elemental analysis methods. The nontoxicity and cell proliferation of samples in addition to their open and accessible interconnected porous network are in favor of tissue integration and vascularization and it shows the potential of CA fibers for scaffold or drug delivery applications [50; 56]. The textile production from CA fibers will lead to unique constructs with a macro/microporous structure emerging from the space between microfibers and mesoporous structure originating from porosity of each aerogel fiber; this also enhances the surface to volume ratio of the end product which is favorable for transdermal, wound care, and tissue engineering applications [2; 57].