Electrochemical sensor for alkaline phosphatase as biomarker for clinical and in vitro applications

Abstract

Alkaline phosphatase (ALP) is an important biomarker of bone diseases clinically measured in blood as a routine assay by means of optical read-outs, which when compared with electroanalytical methods present lack of miniaturization, slow response and high cost. Thus, electrochemical ALP sensors have arisen as a tool to develop disposable low cost devices with an increased sensitivity for healthcare. However, few of them comply with clinical standards, hence, limiting their application and competitiveness compared to the traditional optical methods. Therefore, we address a rapid test for ALP determination in human samples based on an end-point electrochemical assay using disposable graphite screen-printed electrodes and following international clinical recommendations. Using Square Wave Voltammetry (SWV), we first evaluated the electrochemistry of the enzymatic product phenol both at commercial ALP samples as well as at in vitro samples from osteoblasts cell cultures. ALP present in human serum and saliva from patients under normal and pathological conditions was further quantified by SWV. Additionally, the bone ALP isoform of such human samples was measured via precipitation with lectin wheat germ agglutinin. The resulting sensor showed an operational range between 20 to 1500 U L−1 using 10 μL of sample, a total volume of 100 μL and a reaction time of 10 min at 37 °C in addition to no interference of human samples in the potential window of interest for phenol oxidation. This work demonstrates that the electrochemical ALP sensor, here developed, is a promising alternative against the traditional commercial methods currently used.