To test whether the response would be concentration dependent, we spiked two SWCNT suspensions with different concentrations of this analyte pair. For PEG-PL-SWCNTs, solely the enzymatic product (BB) lead to a fluorescent change (Figure ). Additionally, we observed no absorption of the corresponding substrate (PPD) in the visible spectrum (Figure and). This allowed us to estimate the response during the enzymatic reaction based on the BB concentration. Compared to the traditional read-out format, the PEG-PL SWCNTs responded to 5 -10x lower BB concentrations (Figure ). normalized to value at 50 µM)). Note that PPD was not detectable in the VIS and only marginally modified the fluorescence. Thus, only the read-outs of BB are shown for simplicity (n=3, mean ± SD, raw data in Figure ). (d) (G2T)10-modified SWCNT (0.1 nM) respond to the substrate and the product (both 10 µM, n=3, mean ± SD). (e) Concentration-dependent fluorescence changes of (G2T)10-modified SWCNTs (n=3, mean ± SD, normalized data in Figure ). (f) The relative read-outs define the window for the sensor-based signal amplification (SENSAT) for (G2T)10-modified SWCNTs (≈ 120x). Note that the calculated signal amplification is only based on the product (substrate is not detectable in an absorption read-out). We expect that the nanosensor sensitivity for the substrate further enhances the observed signal amplification. Fits are linear for absorption data and modified Langmuir adsorption model (see text) with an offset for nanosensor responses (Fit parameters: Table -S3, SENSAT for PEG-PL in Figure ).