Lab-made disposable screen-printed electrochemical sensors and immunosensors modified with Pd nanoparticles for...

A new conductive ink based on the addition of carbon black to a poly(vinyl alcohol) matrix is developed and investigated for electrochemical sensing and biosensing applications. The produced devices were characterized using morphological and electrochemical techniques and modified with Pd nanoparticles to enhance electrical conductivity and reaction kinetics. With the aid of chemometrics, the parameters for metal deposition were investigated and the sensor was applied to the determination of Parkinson's disease biomarkers, specifically epinephrine and α-synuclein. A linear behavior was obtained in the range 0.75 to 100 μmol L^-1 of the neurotransmitter, and the device displayed a limit of detection (LOD) of 0.051 μmol L^-1. The three-electrode system was then tested using samples of synthetic cerebrospinal fluid. Afterward, the device was modified with specific antibodies to quantify α-synuclein using electrochemical impedance spectroscopy. In phosphate buffer, a linear range was obtained for α-synuclein concentrations from 1.5 to 15 μg mL^-1, with a calculated LOD of 0.13 μg mL^-1. The proposed immunosensor was also applied to blood serum samples, and, in this case, the linear range was observed from 6.0 to 100.5 μg mL^-1 of α-synuclein, with a LOD = 1.3 µg mL^-1. Both linear curves attend the range for the real diagnosis, demonstrating its potential application to complex matrices.