Alginate is a common material in tissue engineering applications and can be modified by oxidation. After oxidation, a faster degradation rate and more reactive groups compared to native alginate are present. The resulting alginate dialdehyde (ADA), can thus be crosslinked with molecules exhibiting primary amino groups via Schiff base reaction. In our study, ADA was crosslinked with gelatin (GEL), and the mechanical properties as well as degradation behavior of ADA-GEL hydrogel films were investigated as a function of the cross-linking conditions.
Compression tests were performed in order to characterize the mechanical properties of ADA-GEL films. The obtained Young’s Moduli were compared directly after cross-linking for various crosslinking conditions, namely the cross-linking time, concentration and ion. Additionally, these values were correlated with the water content of the samples. Moreover, the influence of these conditions on the degradation behavior was investigated over a period of 14 days in cell culture conditions. Apart from this, other factors, such as weight gain/loss, Ca-Ion release and gelatin release were followed.
Results and discussion
By varying the crosslinking conditions, different hydrogels with stiffnesses between approximately 10-200 kPa could be produced. Furthermore, the crosslinking time was shown to only minorly affect the initial stiffness. A more pronounced effect on stiffness was obtained by changing the cross-linking ion from Ca2+ to Ba2+. Moreover, the degradation study showed that all samples undergo a significant weight loss during the first day of incubation, which is most likely due to a burst release of non-crosslinked gelatin.
Through various cross-linking conditions, it is possible to tailor the stiffness as well as the degradation behavior of ADA-GEL hydrogels. Once this behavior is fully understood, the ADA-GEL system can be conveniently tuned for tissue engineering and biofabrication.