The reagentless and oxygen-independent biosensors for ethanol were developed based on the covalent immobilization of alcohol dehydrogenase (ADH) and its cofactor nicotinamide adenine dinucleotide (NAD + ) on chitosan (CHIT) chains. The CHIT-NAD + -ADH structures were adsorbed onto carbon nanotubes (CNT) in order to provide a signal transduction based on the recycling of redox states of NAD cofactor at CNT (detection limit, 8-30 mM ethanol; dynamic range up to 20 mM). The CHIT-NAD + -dehydrogenase/CNT hybrid material represents a general approach to the development of dehydrogenases-based electrochemical biosensors. Interestingly, the CHIT-NAD + solutions preserved their enzymatic activity even after five years of storage at 4 8C.