Study of a low-cost sensitive point-of-care testing system using screen printed biosensors for early biomarkers detection related to Alzheimer disease

Among neurodegenerative diseases, Alzheimer Disease (AD) represents one of the most serious pathology, for which an early diagnosis is still missing. A peculiar expression of an altered conformational isoform of p53 protein was reported to be a biomarker able to distinguish AD subjects from healthy population, quantifiable using a blood-based enzyme-linked immunosorbent assay (ELISA). In order to overcome ELISA limitations related to reliability and to improve sensitivity, this study aimed to realize a low cost highly sensitive portable point-of-care (PoC) testing system based on screen printed electrochemical sensors (SPES). The development of the platform specifically included both the design of the sensing probe and of the electronic circuit devoted to the conditioning and acquisition of the transduced electric signal. In particular, silver, carbon and silver-silver chloride were selected respectively to realize conductive tracks, working and counter electrodes, reference electrode in a three-electrodes configuration focusing on Anodic Stripping Voltammetry (ASV). The conditioning circuit was designed following the scheme for a common potentiostat, and produced as a Printed Circuit Board (PCB). Initial testing of the circuit were performed recording changes in the conductivity of NaCl solution and quantifying electrodes coating with antibodies using Electrochemical Impedance Spectroscopy (EIS) principle. Preliminary results obtained with saline solution, showed the ability of the circuit to give the best response corresponding to low changes in NaCl concentration (sensitivity 13 mA/(mg/ml)), suggesting a good sensitivity of the platform. Results from EIS showed the ability of the circuit to discriminate between different concentrations of antibodies coatings (sensitivity 70 mA/μg). The study is on-going and after a proper calibration, the circuit is intended to be optimized to quantify unknown concentration of unfolded p53 in samples of real patients, compared results with the one from ELISA analysis, aiming to realize a low cost, easy usable and highly precise platform.