Abstract: Disclosed herein are embodiments of a electrochemical sensor device for rapidly determining whether a sample comprises analytes of interest. In particular embodiments, the analytes of interest are biomarkers associated with a physiological condition or disease. The electrochemical sensor device comprises a substrate-based platform having a working electrode comprising functionalized nanotubes that are functionalized with a metal ion and/or a polymer component. In some embodiments, the functionalized nanotubes comprise nanotubes prepared by a double anodization method that provides nanotubes having an average length greater than 3 ?m. In some additional embodiments, the substrate-based platform can comprise a substrate made of a fiber-based material.