## Results and Discussion  
### Preparation and Properties of the pDMYO- and pDSIS-Gels  
The decellularization of porcine myocardial and small intestinal submuc tissues were performed according to previously reported methods [11; 19] (Figure 1A). After decellularization, there was no cell residue visible in either two materials stained with H&E (Figure 1B). The DNA content was 56.39 \(\pm\) 1.0404 ng per mg in pDMYO, and5.90 \(\pm\) 1.5151 ng per mg in pDSIS, which is close to or lower than the minimum content (50 ng per mg) reported in a review [20]. These parameters met the basic biological safety criteria required for decellularized matrix materials prepared from biological tissues. GAG content was significantly higher in pDMYO (2.69 \(\pm\) 0.33 \(\upmu\)g per mg) than in pDSIS (1.39 \(\pm\) 0.30 \(\upmu\)g per mg), while collagen content was slightly lower in pDMYO (156.98 \(\pm\) 15.08 \(\upmu\)g per mg) than in pDSIS (178.54 \(\pm\) 2.07 \(\upmu\)g/mg), which indicates that there was more GAG in pDMYO than in pDSIS (Figure 1C). As for the reason why the amount of GAG per mg of matrix decreases in decellularized material compared with non-decellularized material, yet the amount of collagen per mg increases. Firstly, the water content of fresh raw materials is higher than that of decellularized material. Therefore, the relative content of collagen in decellularized matrix material is increased compared with that in fresh raw materials. As for the content of glycosaminoglycan after acellularization, it is lower than that of fresh materials. The possible reason is that the decellularization method used in our study has a lower impact on collagen and a greater impact on GAG glycosaminoglycan. For example, Triton-X100 is a representative non-ionic detergent, which can effectively separate cell membrane-membrane connection and membrane-protein connection, while has little damage to protein-protein connection. Analysis by electrophoresis  
Figure 1: Preparation and properties of pDMYO-, pDSIS-, and COL1-gels. (**A**) Preparation of pDMYO- and pDSIS-gels; (**B**) H&E staining of porcine non-decellularized myocardial matrix (pNMYO) and porcine decellularized myocardial matrix (pDMYO), scale bar = 100 \(\upmu\)m; H&E staining of porcine non-decellularized small intestinal submuc matrix (pNSIS) and porcine decellularized small intestinal submuc matrix (pDSIS), scale bar = 50 \(\upmu\)m; (**C**) The contents of DNA, GAG and collagen innon-decellularized and decellularized materials; (**D**) Analysis of protein content in the three gels by SDS-PAGE. (**E**) Comparison of the three gels by scanning electron microscopy; (**F**) Comparison of the elastic modulus of the three gels. * denotes statistical difference within the same group with \(p<0.05\), respectively (\(n=3\)). showed that pDMYO contained more low molecular weight proteins than pDSIS, which indicated a higher complexity of the pDMYO components (Figure 1D). Compared with other hydrogels such as chitosan hydrogel [6], alginate hydrogel [7], hyaluronic acid hydrogel [8], the best of advantages is that there are more biological components in pDMYO-gel, including collagen, GAG and other low molecular weight proteins. This means that pDMYO-gel can be used to repair myocardial infarction alone or with other bioactive substances or cells, while other hydrogels usually are used as carriers only for carrying cells or other bioactive substances to repair myocardial infarction. The analysis by SEM showed that our method of decellularized matrix preparation by digestion and jellification of two different tissues could successfully generate hydrogels with suitable nanofiber structures (Figure 1E). Fiber diameter in pDMYO-gel, with loose structure, was about 101.4 nm, while fiber diameter in pDSIS-gel was 58.8 nm, which was close to that found in collagen hydrogels (about 53.1 nm). These diameters were consistent with those previously reported for similar materials [21].