The build up of biocompatible and biodegradable free standing polyelectrolyte multilayer membranes consisting in poly(L-lysine) and hyaluronic acid is presented. Different methods were applied for the film detachment from the underlying substrate leading to membranes with specific porosity and roughness as observed with confocal microscopy and atomic force microscopy. The possibility to functionalize these membranes is demonstrated by the incorporation of an enzyme, alkaline phosphatase, which displays constant biological activity during at least 1 week. These new free standing natural membranes could be an original way to build up bioactive patches carrying specific drugs. This open the route for the build up of "biopatches" able to possess specific biological properties and useful for future biomedical applications. (c) 2005 Elsevier B.V. All rights reserved.