A disposable dual-output biosensor to detect program death-ligand 1 (PD-L1) was developed for immunotherapy progress monitoring and early cancer detection in a single experimental setup. The aptamer probe was assembled on rGO composited with carboxylated terthiophene polymer (rGO-pTBA) to specifically capture PD-L1 protein labeled with a new redox mediator, ortho-amino phenol para sulphonic acid, for amperometric detection. Each sensing layer was characterized through electrochemical and surface analysis experiments, then confirmed the sensing performance. The calibration plots for the standard PD-L1 protein detection revealed two dynamic ranges of 0.5-100.0 pM and 100.0-500.0 pM, where the detection limit was 0.20 ± 0.001 pM (RSD ≤5.2%) by amperometry. The sensor reliability was evaluated by detecting A549 lung cancer cell-secreted PD-L1 and clinically relevant serum levels of soluble PD-L1 (sPD-L1) using both detection methods. In addition, therapeutic trials were studied through the quantification of sPD-L1 levels for a small cohort of lung cancer patients. A significantly higher level of sPD-L1 was observed for patients (221.6-240.4 pM) compared to healthy individuals (16.2-19.6 pM). After immunotherapy, the patients' PD-L1 level decreased to the range of 126.7-141.2 pM. The results indicated that therapy monitoring was successfully done using both the proposed methods. Additionally, based on a comparative study on immune checkpoint-related proteins, PD-L1 is a more effective biomarker than granzyme B and interferon-gamma.
Keywords: Cancer diagnosis; Cancer immunotherapy; Conducting polymer composite; Dual-detection biosensor; Program death-ligand 1.
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