## 4 Conclusions  
The presence of sodium hyaluronate on chitosan was demonstrated by FTIR, Raman, XPS, and XRD. These techniques also allowed to identify the crosslinking potential of PEGDE not only for chitosan but also hyaluronic acid. The addition of a second biocompatible polymer (HNa) to chitosan did not affect degradation temperature as demonstrated by TGA experiments but it reduced its crystallinity as showed by XRD. In fact, crosslinking with PEGDE to CHT-HNa (15%) blends increased thermal decomposition (T\({}_{\text{d2}}\)) possibly due to complex formation and/or the formation of an interpenetrated polymer network. CHT-HNa films showed better adhesion and cell viability with HNa (15%) when crosslinked with PEGDE1, i.e., at low concentration of the crosslinking agent. However, an excess of HNa (30%) did not improve their cell viability even when the surface roughness was increased. In contrast, glutaraldehyde crosslinked samples did benefit from the addition of hyaluronic acid by lowering their DMEM contact angle. Crosslinked blends of CHT and HNa did not show antibacterial activity towards Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus but a low to mild response against Salmonella typhimurium. This latter behavior was achieved only with high crosslinking concentrations of PEGDE and in the presence of glutaraldehyde with a CHT of medium molecular weight CHT (223,332 g mol\({}^{-1}\)) and a degree of deacetylation of 84.1%. These results stress the importance of the properties of chitosan and the type of strain used to assess the claimed antibacterial behavior of chitosan. Nonetheless, its non-sticky nature can be further used in the treatment of ulcers (oral thrush), in which not only a low to mild antibacterial activity is needed but also reparative properties are required in the oral mucosa. In this sense, crosslinking with PEGDE will be beneficial because it retains hyaluronic acid, a compound highly soluble in water and that can be easily dissolved when it is not chemically bound to chitosan. Figure 10: Antimicrobial activity against _S. typhimurium_ of chitosan discs; **(a)** Control, **(b)** CHT, **(c)** CHT/HNa15, **(d)** CHT/HNa15%/PEDGE3, **(e)** CHT/HNa15%/GA. Before 24 h (top) and after 24 h (bottom) of inoculation. **Supplementary Materials:** The following are available online at [[https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)]([https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)) 7/11/3/1267/s1, Figure S1: Individual FTIR spectra of PEGDE crosslinked CHT films with HNa 15% and HNa 30%. Figure S2: Pristine CHT Raman spectra. Figure S3: Pristine HNa Raman spectra Figure S4: XPS scans for C, O and N, of chitosan/HNa films. S5 Swelling behaviour of HNa-free PEGDE crosslinked CHT films. S6 Phosphate buffer saline mass loss of HNa-free PEGDE crosslinked CHT films. **Author Contributions:** All authors collaborated in the design of the research study and manuscript writing. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was supported by the Consejo Nacional de Ciencia y Tecnologia (CONACYT) under grants projects 248378, 1360, 268595, 283972 and the PhD scholarship 339277. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to its content is part of a PhD Thesis. **Acknowledgments:** The authors thank [PERSON] and [PERSON] for XRD and [PERSON] for XPS experiments at Laboratorio Nacional de Nano y Biomateriales (LANBIO), Cinvestav-IPN, Unidad Merida (Projects FOMIX-Yucatan 2008-108160 and CONACYT LAB-2009-01 no. 123913). The authors also wish to thank [PERSON] for AFM analysis. **Conflicts of Interest:** The authors declare no conflict of interest.