Figure 4.

Fluorescence signal intensity of products versus preconcentration time shows an enhanced trypsin-catalyzed reaction with preconcentration. We used three different trypsin concentrations ranging from c_trypsin = 10 pg/ml to c_trypsin = 1 ng/ml (lower concentrations than those used in Figure 3) for enzymes while maintaining the same substrate concentration at c_substrate = 50 μg/mL. The reaction time required to turn over the substrate at a concentration of 1 ng/ml was only ~ 10 min, which was 6 times faster than that without preconcentration. It also showed that the limit of detection was lowered down to c_trypsin = 10 pg/mL, which means a ~1000 folds sensitivity enhancement compared with the results without preconcentration. The fluorescence images were taken at c_trypsin = 10 pg/mL after different concentration times.