Desenvolvimento de sensor eletroquímico para eletroanálise de homocisteína via eletrodo magnético modificado com polímeros impressos molecularmente.

Abstract

Homocysteine (2-amino-4-mercaptobutyric acid; Hcy), a thiolated amino acid, is produced in the metabolism process of the essential amino acid methionine. Normal levels of Hcy in plasma of healthy individuals are between 5 and 15 μmol L-1. Higher concentrations of Hcy give rise to hyperhomocysteinemia (with Hcy up to 100 μmol L-1) which is associated with different diseases. At high plasma levels, Hcy is a risk factor for Alzheimer's and cardiovascular diseases. Therefore, the rapid, sensitive and selective detection of this compound is very important for the diagnosis of diseases. Thus, the present work presents the development of electroanalytical strategies for the determination of Hcy together with a selective approach based on molecularly imprinted magnetic polymers (mag-MIP). Mag-MIP was synthesized via precipitate polymerization, using Hcy as a model molecule, 2-hydroxyethyl methacrylate as a functional monomer and trimethacrylate of trimethyllolpropane (TRIM) as a structural monomer. The morphological and physical characteristics of these materials were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), electrochemical impedance spectroscopy (EIS) and vibrant sample magnetometry (VSM). Subsequently, the electrochemical behavior of Hcy was investigated on the magnetic electrode of graphite composite (m-GCE) by cyclic voltametry (VC) for the optimization of experimental parameters, from the evaluation of different reaction conditions, amount of adsorbent mass, time, pH and buffer nature. The physical-chemical properties were also analyzed and compared with the respective mag-NIPs – control polymers without selective cavity. In addition, two linear ranges for the m-GEC/MIP sensor were obtained through the analytical curve: 0.1–1 μmol L-1, and 2–70 μmol L-1 with detection limits of 0.030 μmol L-1 and 0.186 μmol L-1, respectively. The determination of Hcy by m-GEC/MIP showed excellent performance in relation to the possible interferences commonly found in biological samples. Finally, the recovery test was performed, with mean recovery values of 100.7 and 105.2% for synthetic plasma and 98.4 and 102.5% for synthetic urine, indicating good accuracy for the proposed sensor. Therefore, through these results it can be inferred that the electrochemical sensor developed is a promising device for the determination of Hcy.