A universal nanostructured bioanalytical platform for NAD-dependent enzymes based on the fluorescent output reading with a smartphone.

A nanostructured surface composed of SiO nanoparticles (200 nm) deposited on fiberglass was used as a platform for immobilization of NAD-dependent enzymes (alcohol and glucose dehydrogenases). The surface functionalized with the enzymes was further loaded with NAD(P)cofactor and 1-methoxy-5-methylphenazinium methyl sulfate (MPMS) redox species. The designed biocatalytic system was used for fluorescent analysis of substrates (ethanol and glucose used as example analyte substances). Importantly, the output analytical signal was obtained by processing fluorescent images of the sensing spots using a smartphone for handling and digitizing the images. The designed sensing interface is suggested as a universal analytical platform which can be used with many different NAD-dependent enzymes. The present biosensing/bioanalytic system was studied as a proof-of-the-concept, rather than as a practically important ethanol or glucose biosensor. Many more practically important biosensors based on the same universal platform can be designed with different enzymes for various biomedical, forensic, and homeland security applications as well as environmental monitoring.