## 3 Results and Discussion
### Characterization of AlBA/TA Hydrogel Thread  
Most commercial suture threads are classified as \"single\" or \"twisted\". Most sutures use twisted threads to increase their mechanical strength. As there is no interaction between braiding, a complicated process is required, in which the threads must be woven multiple times to control the thickness. However, in the AlBA/TA hydrogel state, the thickness could be controlled more easily through the stacking process during layered thread formation, due to reversible crosslinking reactions, which mainly occurred between the boronic acid groups and the cis-diol moieties on the TA molecules. The sticky hydrogel spun through the syringe fused into a single final thread during the process of overlapping and drying. The superimposed hydrogels were not separated during the drying process. The thickness measurements of the manufactured threads were performed by optical microscopy. The thickness values of the one-layer, two-layer, and three-layer fabricated threads were 148.8 \(\pm\) 26.7 \(\upmu\)m, 217.7 \(\pm\) 35.2 \(\upmu\)m, and 318.6 \(\pm\) 68.7 \(\upmu\)m, respectively (Figure 3a). Supposing that an increased thickness might lead to undesirable voids and cracks inside the hydrogel, the strength of the fabricated threads was assessed by  
Figure 2: Physicochemical characteristics of AlBA/TA hydrogels. (**a**) UV–vis spectrum of AlBA aqueous solution. (**b**) Rheological properties of the mixtures of AlBA with various polyphenols: TA (red), pyrogallol (blue), pyrocatech (green), and AlBA alone as a control (black). Storage modulus (G\({}^{\prime}\), filled symbols) and loss modulus (G\({}^{\prime\prime}\), open symbols). (**c**) Changes in rheological moduli of the AlBA/TA hydrogels as a function of AlBA concentration (1, 2, 3, and 4 wt%) at fixed molar concentration of TA (0.01 M). (**d**) Photographs of AlBA solutions at different concentrations corresponding to the hydrogel fibers. Bubbles inside the solution (top red square) generate a rough surface hydrogel thread (bottom red square). employing a universal tensile machine. The values of thread strength were 0.8 \(\pm\) 0.1 N, 1.6 \(\pm\) 0.1 N, and 2.5 \(\pm\) 0.4 N for one, two, and three layers, respectively (Figure 3b). SEM investigation confirmed that the thickness of the two-stacked layer threads is similar to that of a general suture 4.0 (250 \(\upmu\)m) (Figure 3c). At the same time, a linear dependence between strength and thickness of the threads was noticed. Therefore, this facilitates the ease of manufacture of threads with varying thicknesses. Figure 3: (**a,b**) Comparative observation of the thickness (**a**) and tensile maximum load (**b**) of adhesive AlBA/TA threads with different layers. (**c**) Optical microscopy images of commercial suture thread (i) and AlBA/TA threads (iii for 1 layer and iv for 2 layers). SEM image of AlBA/TA thread with 2 layers (ii). (**d**) Changes in maximum tensile stress of AlBA/TA threads with environment pH (\(n\) = 3 or more, mean \(\pm\) SD) (one-way ANOVA, ***\(p\)\(<\) 0.001, ***\(p\)\(<\) 0.0001). (**e**) Dissociation and/or degradation kinetics of TA over time from the AlBA/TA threads in a physiological buffer. (**f**) Stretchability of the swollen AlBA/TA threads at physiological condition. (**g**) 3D mesh constructs fabricated using the swollen AlBA/TA threads. AlBA, the main component of the thread, is pH-sensitive [21]. Similar to alginate, which agglomerates at low pH [18], it was expected that alginate-like AlBA macromolecules would follow the same behavior at acidic pH. Each organ in the body is characterized by a specific pH (stomach: \(\sim\)2.0, terminal ileum: \(\sim\)8.0) [22; 23]. This may affect the thread performance. Therefore, we determined the change in the strength of the yarn (2 layer) based on pH.