Novel selective and sensitive electrochemical sensor for detection of ovarian cancer biomarker, Cathepsin L

Late detection of ovarian cancer is critical as it results in decreased life expectancy of patients. Screening methodology with a rapid turnover is required to ensure better patient outcomes. Till date, no point of care diagnostics exists capable of monitoring epithelial ovarian cancer. Cathepsin L is a classic early-stage biomarker demarcating the proliferation and transition of ovarian cancer. A novel label-free electrochemical diagnostic is proposed for detection of Cathepsin L in serum. Intrinsic fluorescence spectroscopy was used to confirm the interaction between Cathepsin L and probe, Cystatin C. Cystatin C was immobilized on screen-printed carbon electrode using 1-Ethyl-3-(3-dimethyl-aminopropyl carbodiimide and N-hydroxysuccinimide cross linker. Electrochemical fluctuations resulting from Cystatin-Cathepsin interaction was detected by cyclic voltammetry, differential voltammetry and electrochemical impedance spectroscopy within a timeframe of 20 min. The proposed diagnostic for Cathepsin L exhibited analytical performance with a limit of detection upto 70 pg mL^-1 via electrochemical impedance spectroscopy in the dynamic detection range of 2 ng mL^-1-20 ng mL^-1. The platform indicated reliable reproducibility, selectivity, and stability. Furthermore, validation with spiked sera samples (n = 5) showed correlation of R² = 0.98. The results indicate sensitive yet selective point of care diagnosis of Cathepsin L in serum.