- A new process has been developed to determine the biological activity of an intact layer of lysozyme deposited onto a biomaterial surface. This process is applied to a number of common hydrogel contact lenses. The activity of the surface-adsorbed protein is measured using a standard micrococcal activity assay, with extra steps to distinguish between protein on the surface and protein in solution. This is in contrast to protein extraction work in which the activity of all adsorbed protein is measured. For ionic materials, which are known to deposit large amounts of protein, particularly positively charged proteins such as lysozyme, there is evidence for loosely bound protein re-entering the solution, thus making it impossible to truly separate out the surface-adsorbed protein. This optimized process provides the first quantification of the biological activity of an intact layer of surface-adsorbed protein at a hydrogel interface.