To test the binding capacity of a hydrokinetic fiber dressing for PMN elastase, MMP-2 and MMP-9 in vitro, and to determine whether testing of dressing material samples in vitro is sufficient to predict the performance of the whole dressing. In vitro protease binding assays for PMN elastase, MMP-2 and MMP-9 were used to evaluate the protease modulating capacity of sorbion sachet EXTRA, a superabsorbant dressing that consists of special hydrokinetic fibers, which are formed from cellulose and sodium polyacrylate in a mechanical process without any bonding agents or adhesives. The ability of the hydrokinetic fiber dressing to inhibit elastase and collagenase activity was also tested at 0%, 50% and 100% saturation volume. The hydrokinetic fiber wound dressing was able to bind considerable amounts of elastase, reducing elastase activity by approximately 84%. Moreover, it significantly decreased MMP-2 and MMP-9 concentrations in vitro and was able to completely inhibit collagenase activity. In summary, the hydrokinetic fiber dressing sorbion sachet EXTRA was able to significantly reduce the concentration and activity of proteolytic enzymes in vitro. These results suggest that sorbion sachet EXTRA should have a beneficial action by reducing the detrimental effects of proteolytic enzymes in vivo. This work was supported by Sorbion GmbH & Co. KG, Senden, Germany.