The present work describes an exciting method for the generation of stable silica-molecularly imprinted polymer (MIP) composite fibers, via a non-hydrolytic sol-gel simple route, using carboxylated multi-walled carbon nanotubes. The modified MIP-composite fibers were used as an electrochemical sensor for the selective and sensitive analysis of ultra-trace level of 5-fluorouracil and uracil in aqueous, blood plasma, and pharmaceutical samples. Such sensors could be considered cost-effective, renewable, disposable, and reliable for in-field and clinical studies, without any cross-reactivity and matrix effect from real samples [limit of detection (3 sigma, aqueous solution); 1.30 ng mL(-1), 5-fluorouracil and 0.56 ng mL(-1), uracil]. (C) 2012 Elsevier Ltd. All rights reserved.