Here, we show that fluorescent nanosensors amplify the signal of enzymatic reactions typically used in ELISAs. To this end, we identify SWCNT surface modifications that are sensitive to substrates or products of important enzymes (β-galactosidase and horseradish peroxidase). We investigate how the signal scales with analyte concentration and develop a theoretical model for signal enhancement. This approach presents a generic concept to increase chemical signals and translate it into a beneficial spectral window.