Electrochemical substrate for active profiling of cellular surface leucine aminopeptidase activity and drug resistance in cancer cells

Leucine aminopeptidase (LAP) is an essential proteolytic enzyme and potential biomarker for liver malignancy. Overexpression of LAP is directly linked with some fatal physiological and pathological disorders. In this regard, we have designed an activity based electrochemical substrate leucine-benzyl ferrocene carbamate (Leu-FC) for selective profiling of LAP activity in live cells. In practice, LAP instantaneously hydrolyze the Leu residue of the substrate Leu-FC to eliminate the unmasked electrochemical reporter amino ferrocene via predefined self-immolative cascade. The electrochemical signal is distinctly specific for LAP and free of other electroactive biological interference. The substrate Leu-FC empowered sensor displayed broad dynamic range with admirable detection limits. On top of this, the probe Leu-FC was employed in real-time active profiling of cellular LAP activity in HepG2 cells and effect of LAP inhibitor. In extent, the substrate Leu-FC can effectively monitor cisplatin induced overexpression of LAP activity in HepG2 cells in presence and absence of bestatin. The sensor showcased an excellent reliability towards monitoring cellular LAP activity in HepG2 cells. Unlike the traditional antibody-based immunoassays, our approach is capable of monitoring in-situ activity of LAP in live cells.