## 4 Conclusions  
Macroporous cryogels based on gelatin, chitosan, and chondro sulfate were synthesized using the cryogelization method (\(-\)12 \({}^{\circ}\)C) at various CS concentrations using the physical and chemical method of crosslinking. The presence of characteristic functional groups was confirmed by IR spectroscopy. This paper investigated the effect of linear GAG such as CS on the physicochemical properties of Gel/Ch cryogels. As the study has demonstrated, with an increase in the content of chondro sulfate, a decrease in porosity was observed and the density of cryogels increased, which led to the formation of a macroporous structure of polymers. The content of the gel fraction for the GelChCS50 cryogel was the highest (\(\sim\)81%). The swelling capacities of the cryogels GelChCS10, GelChCS25, and GelChCS550 were the highest; however, the studies on biodegradation showed that the cryogels GelChCS50 and GelChCS100 had the least degree of biodegradation in PBS and retained most of their shape for 8 weeks. SEM studies also revealed the most uniform pore distribution in the GelChCS50 cryogel, which is suitable for cell proliferation. The thermogravimetric analysis showed that when the temperature rose to 800 \({}^{\circ}\)C, the weight loss of the crosslinked samples was 80% on average, while for the non-crosslinked sample it was 95%. The glass transition temperature for the non-crosslinked sample was also lower compared to that of the crosslinked cryogels. An in vitro study of cytotoxicity showed that the synthesized cryogels are not toxic. Since cryogels are composed of natural polymers, it is expected that degradation products will not cause problems with immune rejection during implantation, which in turn makes such materials promising for applications in the  
Figure 6: Effects of GelChCS extracts on viability of rat ADMSC presented as percentage of cell viability versus concentration of the extracts. The experiments were repeated in triplicate independently, and the data are expressed as the means \(\pm\) SD with \({}^{\star}p<0.05\); \({}^{\star}\)\({}^{\star}\)\(p<0.0001\). treatment of bone disease. In the future we plan to use cryogels for preclinical study on the treatment of damaged intervertebral discs, since biopolymers used in our study are the main ECM components of the intervertebral disc. The following are available online at [[https://www.mdpi.com/article/10.390/app112110056/s1](https://www.mdpi.com/article/10.390/app112110056/s1)]([https://www.mdpi.com/article/10.390/app112110056/s1](https://www.mdpi.com/article/10.390/app112110056/s1)), Figure SI: SEM images and histogram of pore sizes of the cryogels: (a) GelChCS10, (b) GelChCS25, (c) GelChCS50, (d) GelChCS100, and (e) GelChCS250. Scale bar = 100 \(\upmu\)m.  
Conceptualization, G.K. and V.O. ; methodology, G.K., M.Z. and V.O. ; software, M.Z. ; formal analysis, E.A.M. and A.A.; investigation, G.K. and E.A.M. ; writing--original draft preparation, G.K. and M.Z. ; writing--review and editing, G.K. and E.A.M. ; funding acquisition, G.K. All authors have read and agreed to the published version of the manuscript. This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08052556). This study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Local Ethics Committee of the National Center for Biotechnology (number NCB-04-2020). Not applicable. All data presented in this paper are available upon request from the corresponding author. The authors thank [PERSON] (Istanbul Technical University, Turkey) for helpful discussion of the manuscript. The research was financially supported by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Research program No. OR11465426). Figure 1 and the graphical abstract were created with [[https://biorender.com/](https://biorender.com/)]([https://biorender.com/](https://biorender.com/)) (accessed on 25 October 2021).