In addition, interlacing the electrostatically assembled bPEs with the covalent GelMA scaffold led to protection against indefinite swelling -a drawback typically faced by PEC hydrogels. When exposed to a solvent bath, the GelMA/bPE hydrogels swelled until they reached equilibrium within several hours. To monitor the retention of bPEs in the hydrogels, mass release during and after completion of swelling was monitored over a period of 14 days (Figure ). All hydrogel samples contained the same gelatin mass before being immersed in water. For both GelMA and hybrid hydrogels, an initial loss of material was expected attributed to the release of unfunctionalized gelatin chains as well as photoinitiator residues. Since GelMA/TbPE hydrogels did not show any additional mass release compared to GelMA (identical absolute mass loss), we conclude that the interpenetration of electrostatic and covalent networks prevented the escape of TbPEs. In contrast, high mobility of disjointed micelles in GelMA/DbPE hydrogels resulted in their fast and almost complete release. Hence, the DbPE additives can be considered as a sacrificial scaffolding which temporarily improves material properties for 3D printing. Accounting for the respective mass loss within the first 24 hours, an "effective" swelling ratio was calculated. The hybrid hydrogels exhibited slightly reduced swelling properties (~ 30%) compared to the GelMA hydrogels (Figure ), attributable to a combination of increased polymer concentration, entanglements, and crosslink density in the hydrogels that limited network expansion and reduced swelling.