Based on polymeric nanotechnologies, enzyme sensors and microreactors have been developedin the way, that they can determine urea in liquids. The technology of manufacturing an enzymatic biosensor does not differ significantly from the known technology of manufacturing microcapsules with an enzyme by the laer-by-laer method. This allows us, when constructing a biosensor, to use the information obtained on encapsulated enzymes by other authors. It is shown that urea biosensor is able to work for a long time (up to 2 months) without significant loss of enzyme activity. Polymer technology for manufacturing sensors is less laborious and expensive compared to other similar technologies. We propose to develop biosensor devices – urea analyzers with polymer enzyme chips for express diagnostics of biological fluids (blood, urine). One of the significant results of this work from our point of view is two factors. The first factor is the optimization of the conditions for the production of a functionally active enzyme immobilized in a polyelectrolyte coating, when the enzyme after the immobilization procedure shows an activity comparable to that of a freshly prepared free enzyme. Such a result will allow reducing the cost of enzymes when creating a sensitive layer of the developed urea analyzer. And the second factor is that the polymer coating with the enzyme is able to work not only as an enzyme electrode, but also as an enzyme microreactor, without decreasing the rate of signal registration after passing the catalytic urease-urea reaction.