Patent ID: 7611860

Claim:
An indicator suitable for detecting at a location the presence of lysozyme or the presence of nicotinamide adenine dinucleotide (NADH) in the presence of lysozyme, wherein the indicator comprises: (a) a biopolymer layer which is susceptible to degradation by lysozyme; and (b) a signaling layer which comprises an indicator substance, which layer is adapted to produce a detectable signal upon contact with lysozyme or upon contact with NADH in the presence of lysozyme; wherein, in use, the signaling layer (b) is at least initially protected from contact with NADH by the layer (a), and wherein the signaling layer (b) is adapted to produce a detectable signal whose initial strength is proportional to the amount of NADH or lysozyme, and wherein the signaling layer (b) further comprises a pH indicator or assay reagents for detecting an additional enzyme, an immune cell or a micro-organism.