Indirect detection of acid phosphatase at the macroscopic electrified liquid-liquid interface

Abstract

Acid phosphatase (AcidP) is a biomarker of prostate cancer (PC) when found in blood and urine at elevated levels. Moreover, AcidP could also be used as a target biomarker in presumptive test for the presence of semen in case of sexual assault. Therefore, this preliminary work proposes an alternative approach for the electrochemical (cyclic voltammetry) detection of AcidP having specific activity ≥0.4 unit·mg−1 over electrified liquid-liquid interface (eLLI). Proposed idea is simple and based on the reaction catalyzed by AcidP, this is hydrolysis of phosphocholine ester (PCE) resulting in the production of choline that generate electrochemical signal upon potential difference controlled transfer across the eLLI. Mechanisms, interfacial behavior, physicochemical parameters pertaining to choline, PCE and AcidP have been studied using cyclic voltammetry. Observed optimal parameters were employed for the indirect detection of the AcidP in the presence of PCE. We have found that when the mixture of AcidP and PCE were incubated for 24 h at 37 ˚C in 10 mM Britton-Robinson-Buffer (pH 4.8) the clear signals attributed to choline transfer started appearing within the available potential window. Even with very low specific activity of AcidP (only 0.4 unit·mg−1), eLLI based enzyme biosensor demonstrated a linear detection range from 0.4 to 2.0 mg·mL−1 with experimental detection limit of 0.4 mg·mL−1. Moreover, sensitivity of the proposed biosensor was found 5.15 µA·L·g−1. Results obtained in this study can be considered as the proof of concept with high potential for the detection of AcidP in real clinical and forensic samples.