Banca de DEFESA: JOSE EUDES DA SILVA DE OLIVEIRA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JOSE EUDES DA SILVA DE OLIVEIRA
DATE: 30/07/2024
TIME: 14:00
LOCAL: VIRTUAL
TITLE:

DEVELOPMENT OF ELECTROCHEMICAL SENSORS FOR SIMULTANEOUS QUANTIFICATION OF BIOMARKERS 7-METHYL-GUANINE, 3-METHYL-ADENINE AND 5-METHYL-CYTOSINE

KEY WORDS:

DNA Methylation, 5-methylcytosine, 7-methylguanine, 3-methyladenine, borondoped diamond electrode, glassy carbon electrode, voltammetry, impedance.

PAGES: 108
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Analítica
SPECIALTY: Eletroanalítica
SUMMARY:

The identification of human disease biomarkers such as methylated DNA adducts in biological samples is of great importance. In this context, the main objective of this work was to investigate, for the first time, the electrocatalytic oxidation of 7-methyl-guanine (7-mGua) and 5-methyl-cytosine (5-mCyt) in a boron doped diamond electrode pre-tretaed cathodically treated (red-BDDE), using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The anodic peak potentials of 7-mGua and 5-mCyt by DPV were observed at E = 1.04 V and E = 1.37 V at pH = 4.5, indicating excellent peak separation of approximately 330 mV between species . Using DPV, experimental conditions such as supporting electrolyte, pH and influence of interferents were investigated to develop a sensitive and selective method for the individual and simultaneous quantification of these biomarkers. The analytical curves for the simultaneous quantification of 7-mGua and 5-mCyt in acidic medium (pH = 4.5) were: concentration range of 0.50–5.00 μmol L-1 (r = 0.999), limit of detection of 0.27 μmol L-1 for 7-mGua; and from 3.00 to 25.00 μmol L-1 (r = 0.998), with a detection limit of 1.69 μmol L-1 for 5-mCyt. A new method from DPV for the simultaneous detection and quantification of the biomarkers 7-mGua and 5-mCyt using red-BDDE was then proposed. The electrooxidation of 3-methyladenine (3- mAde) in aqueous electrolytes on carbon electrodes (GCE and red-BDDE) was investigated by voltammetric techniques and electrochemical impedance spectroscopy (EIS). Different experimental factors were explored, such as the influence of concentration, composition and pH of the medium, mass transport, adsorption of products on GCE and BDDE surfaces and the presence of possible interferences in the oxidation of 3-mAde. The electrochemical data demonstrated that the methyl group is not electroactive, but strongly influences the oxidation mechanism of 3-mAde. The anodic behavior of 3-mAde on GCE and BDDE occurred by mass transport by diffusion, in a single irreversible pH-dependent step, in a reaction at the electrode with the removal of an electron and a proton. By cyclic voltammetry, the diffusion coefficient of 3-mAde was established at physiological neutral pH (D3-mAde = 1.57∙10-5 cm2 s -1 ). Compared to adenine, the oxidation of 3-mAde occurred at more positive potential values (~200 mV), thus allowing simultaneous voltammetric determination of both bases. Recovery experiments were performed and additions of 3-mAde with known concentrations were made to samples prepared from mixtures of free DNA bases and the 7-mGua adduct. The results on the GCE sensor in acetate buffer (pH = 4.5) were quite satisfactory (96.4 – 101.3% recovery), indicating excellent precision and accuracy, as well as advantages such as simplicity, speed and cost of the proposed method. New methods with GCE and red-BBE using DPV to determine 3-mAde in acetate buffer (pH = 4.5) and phosphate buffer (pH = 7.0) were also proposed. Thus, overall this work proposes new sensitive and selective electrochemical sensors, using DPV and functionalized carbon electrodes for the simultaneous detection and quantification of important biomarkers of human diseases, such as 7-mGua, 5-mCyt and 3-mAde, contributing significantly to the advancement of electroanalytical techniques in biomedical research.

COMMITTEE MEMBERS:
Presidente - SEVERINO CARLOS BEZERRA DE OLIVEIRA
Interno - MARCILIO MARTINS DE MORAES
Interno - RAMOM RACHIDE NUNES
Externo à Instituição - ERIC DE SOUZA GIL - UFG
Externo à Instituição - VAGNER BEZERRA DOS SANTOS - UFPE