## 3 Result and Discussion  
### Characterization of PGC Composite Films  
FTIR spectra analyses were performed to confirm the chemical nature of the PGC films. The FTIR spectrum of chitosan, gelatin, PVP, and PGC composite film can be seen in Figure 1. In spectra of chitosan showed characteristic bands at approximately 1629.6 cm\({}^{-1}\), 1556.3 cm\({}^{-1}\), and 1407.9 cm\({}^{-1}\), corresponding to amides I, amides II, and vibrations of -OH groups, respectively. A broad peak at 3278.6 cm\({}^{-1}\) was found, indicating stretching vibration due to the N-H and O-H bonds. In addition, the spectrum of gelatin shows some characteristic bands around 3280.5 cm\({}^{-1}\), 1633.5 cm\({}^{-1}\), 1535.1 cm\({}^{-1}\), and 1240.1 cm\({}^{-1}\), corresponding to amides A, amide-I, amide-II, and amide-III, respectively. The spectra of PVP shows characteristic bands at 1656.6 cm\({}^{-1}\), which corresponds to the stretching vibration of the C=O group, and the apparent absorption peak at 1276.7 cm\({}^{-1}\) is attributed to the stretching vibration of C-N. The spectra of the PGC composite shows a peak at 1550.6 cm\({}^{-1}\), which is the C=N functional group produced by gelatin and chitosan through glutaraldehyde cross-linking.  
The ideal wound dressings should be soft, firm, and be able to retain their structure such that they do not degrade rapidly due to excess swelling from absorbing large amounts of body fluid. The water content of PGC composite films is showed in Table 2. The water content of each group is higher than 90%, and the PGC111 film is smaller than the other sample. Because gelatin and chitosan molecules contain hydrophilic groups, the content of gelatin and chitosan in the PGC111 film is significantly lower than that of the other groups. Therefore, hydrogen bonding between the water molecules is also reduced. The mechanical properties of PGC111 and PGC121 swollen films are so weak that they broke at the beginning of the tensile test, so mechanical property data could not be obtained (data  
Figure 1: FT-IR spectrum of chitosan, PVP, gelatin, and PGC composite films.  
not shown). In another study, the CS film had a Young's modulus of 1.92 GPa. When 50% of PVP is added into CS, the Young's modulus decreases [25]. When the hydrogel-like material is in the swelling state, the Young's modulus will also decrease. In our study, the Young's modulus of the PGC materials is also similar. Another approach is to chemically cross-link chitosan (CS) and boost its mechanical stability without subsuming the baleful chemicals involved in utilizing oxidized polysaccharides. Oxidized cellulose (OC) was subsumed with CS. The inclusion of 5% OC (relative to CS's weight) into CS films escalated their tensile strength from 51.9 to 74.7 MPa [26]. In our study, The PGC films were crosslinked in glutaraldehyde vapor at room temperature for 15 min. Compared with the above literature data, the increasing trend of the tensile strength of the film is similar.  
In addition, gelatin can absorb up to five to ten times its weight in water [27]. Therefore, the content of gelatin in the PGC composite film will affect its mechanical properties and weight loss in PBS. When the gelatin content in the PGC film is increased, the water content of each group (PGC112 and PGC122) shows no significant difference. However, due to the hydrophilic nature of the PGC122 film, it shows a greater swelling property than the PGC112 film. Therefore, the tensile strength and weight loss of the PGC122 film is significantly decreased (Figure 2). Based on the above result, the PGC112 film has a higher water content ratio and tensile strength, as well as a slow degradation rate and is therefore suitable for use as a base material for wound dressings.