For clinical applications, where the gel is injected to the tissue defect in order to fill the cavity, it is important that the injected hydrogel does not swell too much as prolonged swelling will cause enhanced pressure on the tissue around the injection site and risk the hydrogel popping out of the defect. On the other hand, poor mechanical strength after swelling has always been a major disadvantage of injectable hydrogels. In this study, the swelling ratio (wet/wet swelling ratio) was measured by evaluating the equilibrium hydrogel weight after 24 hours of swelling in PBS at 37 ºC to as prepared weight determined immediately after crosslinking to understand how much collagen furan hydrogel might swell after injection and crosslinking. As shown in Figure , the collagen furan hydrogel showed minor swelling degree of 10 % after 24 hours from the as prepared state. This small extent of swelling was not visible in observations through naked eye (Figure ). As minor swelling was observed, a swelling experiment over 5 days was performed in a similar manner which revealed no significant swelling when compared to 24 hours of swelling (Figure inset). By introducing hydrophobic furan to the collagen polymer chain and further crosslinking with maleimide group, the overall hydrophilicity of the polymer network decreases with concomitant increase in elasticity of the network, leading to lower swelling. ). Error bars represent standard deviation, "***" represents a p-value of 0.001; df represents degrees of freedom; one-way ANOVA, followed by Tukey's test, n = 3 independent samples.