NOVELTY - Material functionalized with NAD+ or NADP+.    USE - The functionalized material is useful for manufacturing biosensors, bioelectrodes, biopiles, biobatteries, or biofuel cell; and for qualitative and/or quantitative determination of enzyme substrate in sample (all claimed). It is useful as a bioelectrode for developing biosensors based on dehydrogenase enzymes and as a bioanode in biobatteries.    ADVANTAGE - The substrate surface has been modified thus taking advantage of the great affinity of the enzymes to efficiently immobilize cofactor and its binding site. The material provides enormous advantages in terms of durability, flexibility and applicability.    DETAILED DESCRIPTION - Functionalized material of general formula (I).    S'=an electrode support;    L=a bridging group comprising formula (II); and    C'=a cofactor that is selected from NAD+, NADP+, NADH or NADPH, where C' binds L that is covalently linked via the primary amino group at position 6 of adenine of C'.    INDEPENDENT CLAIMS are:    (1) a method of producing the material which involves: (a) epoxidation of the substrate with a compound comprising at least one group of formula (III); and (b) and adding a solution of the product of cofactor obtained in step (a); or a method for obtaining the material which involves: (a) epoxidation of cofactor with a compound comprising at least one group of formula (III); and (b) deposition of product obtained in step (a) on support;    (2) biosensor comprising the functionalized material;    (3) biocell comprising the functionalized material; and    (4) a method for qualitative and/or quantitative determination of an enzyme substrate in a sample comprising: (a) contacting the sample with the biosensor; (b) subjecting the biosensor to conditions resulting in an electrochemical signal; (c) measuring the electrochemical signal obtained in (b); and (d) determining qualitatively and/or quantitatively the substrate from the electrochemical signal measurement.