Optical fiber bioanalyzer based on enzymatic coating matrix for catecholamines and their metabolites assessment in patients with Down syndrome

Abstract

The urinary levels of catecholamines [adrenaline (AD), noradrenaline (NA), and dopamine (DA)] and their metabolites [L-3,4-dihydroxyphenylalanine (L-DOPA), and 3,4-dihydroxyphenylacetic acid (DOPAC)], as indicators of physiological stress, were assessed in 40 patients with Down syndrome (DS). The analysis was performed by an optical fiber (OF) bioanalyzer; which was constituted by two main components: a miniaturized chromatographic system and a detection system based on an OF coated with an enzymatic matrix. In this study some working conditions such as, number of fibers in the miniaturized chromatographic column, number of dips for sensitive coating deposition, temperature and time of cure of the sensitive matrix, were optimized in order to achieve higher analytical performance. After tested for calibration the bioanalyzer was applied to urine samples analysis of catecholamines and their metabolites, comparing the results with those obtained by both, a classical analytical method, namely high performance liquid chromatography coupled to an electrochemical detector (HPLC-ED), and an OF biosensor based on a sensitive cladding of laccase (LacOF biosensor). The results of catecholamines in patients with DS revealed that 15% and 22.5% of the analyzed subjects showed DA and AD concentrations, respectively, above the pathological levels. In the determinations of NA, the 40 samples showed concentration values below the normal levels, while in the determination of catecholamines metabolites 5% of the urine samples showed values above 118 and 1681 for L-DOPA and DOPAC, respectively.