Electrochemical impedance spectroscopy for monitoring caspase-3 activity

•Peptide film was immobilized on a screen-printed gold electrode.•Caspase-3 activity was detected using electrochemical impedance spectroscopy.•Biosensor performance was tested using apoptotic and healthy SH-SY5Y cell lysates.•Biosensor is a promising platform for screening novel caspase-3 inhibitors.

Caspases play a key role in apoptosis and represent important therapeutic targets for treating cancer and inflammatory diseases. In this proof-of-concept study, an electrochemical impedance spectroscopy (EIS)-based biosensor was developed for the analysis of caspase-3 activity in non-diluted biological samples using screen-printed gold electrodes (SPGE) compatible with small sample volumes (i.e. 2 μL). A caspase-3-specific peptide substrate was immobilized on the surface of the SPGE using N-hydroxysuccinimide (NHS)-activated lipoic acid esters. The proteolytic activity of caspase-3 was analyzed using EIS, in which the presence of the enzyme resulted in cleavage of substrate peptides. Changes in the surface-immobilized substrate peptide film were detected using the apparent charge transfer resistance (RAPP) in connection with [Fe(CN)6]3−/4− redox probe. The analytical performance of the biosensor was challenged with undiluted apoptotic human SH-SY5Y neuroblastoma cell lysates at 2-μL aliquots. Control experiments were performed with healthy SH-SY5Y cell lysates and did not display a significant decrease in RAPP values. EIS data were also confirmed using a commercially available optical kit. EIS-based biosensor demonstrated a promising potential to become a versatile tool for rapid screening of caspase-3 proteolytic activity in complex biological samples.

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