Cerebrospinal fluid levels of alpha-synuclein measured using a poly-glutamic acid-modified gold nanoparticle-doped disposable neuro-biosensor system†
Alpha-synuclein (SYN) is a prominent key protein in Parkinson-type dementia. Measurement of the amount of this protein found in the cerebrospinal fluid (CSF) using precise techniques may help in the diagnosis and prognosis of the disease. In this study, a gold nanoparticle (AuNP)–polyglutamic acid (PGA)-modified indium tin oxide (ITO)-based disposable neuro-biosensor system was designed for alpha-synuclein (alpha-SYN), an important biomarker of Parkinson's disease. Glutamic acid was formed by electropolymerization on the electrode surface. The parameters that can affect the performance of the biosensing probe were optimized. The techniques used in the design of the immobilization steps, the optimization studies, and the evaluation of the analytical performance of the targeted neuro-biosensor are electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square wave voltammetry (SWV). Charge transfer resistance (Rct) changes were highly linear and sensitive with the alpha-SYN concentration in the 4–2000 pg mL−1 range and associated with a limit of detection of 0.135 pg mL−1. With the designed disposable neuro-biosensor system, the amount of alpha-SYN found in CSF samples was determined by the standard addition technique and found to be strikingly sensitive to the target analyte. Morphological and chemical changes on the sensing surface were evaluated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). In addition, it was determined that the PGA-modified, AuNP-doped neuro-biosensor system has great reproducibility potency, long storage stability, and regeneration capacity. We suggest that the AuNP–PGA combination platform is ideal for use as a biosensing probe to detect alpha-SYN.