A high swell, long-lived hydrogel sealant formed by reacting a highly oxidized polysaccharide containing aldehyde groups with a multi-arm amine is described. The hydrogel sealant may be particularly suitable for applications requiring high swell and slow degradation, for example, tissue augmentation, both cosmetic and reconstructive void filling tissue bulking, for example treatment of urinary incontinence and acid reflux and embolization. The high swell, long-lived hydrogel sealant may also be useful as a tissue sealant and adhesive, and as an anti-adhesion barrier.
