Biomass-based quantum dots co-doped with sulfur and nitrogen for highly sensitive detection of thrombin and its inhibitor

Abstract

In this study, a facile bottom-up method using garlic and ginger as precursors has been developed to prepare biomass-based quantum dots co-doped with sulfur and nitrogen (S,N-BQDs). The obtained S,N-BQDs with a maximum emission wavelength at 524 nm were then coupled with hortpolypeptide S-2238 to fabricate a fluorescence probe for the detection of thrombin and its inhibitor based on the inner filter effect (IFE). In this sensing system, hortpolypeptide S-2238 was used as the chromogenic substrate of thrombin, which cleaves S-2238 and releases p-nitroaniline (PNA). Since the absorption spectrum of PNA overlaps largely with the excitation spectrum of S,N-BQDs, to the fluorescence of S,N-BQDs is remarkably quenched. Therefore, the structured IFE-based fluorescence nanoprobe was used for the label-free detection of thrombin in a wide concentration range of 0.1–65 nM with a detection limit of 30 pM (S/N = 3). This IFE-based fluorescence nanoprobe was also used for thrombin inhibitor detection as well as thrombin imaging in living cells. This method has many positive features, including flexibility, simplicity, sensitivity and selectivity, which gives new insights into enzyme activity assays that employ biomass co-doped carbon nanomaterials.