EXPLORANDO BIOSSENSORES FOTOELETROQUÍMICOS PARA DETERMINAÇÃO DE MOLÉCULAS DE INTERESSE AMBIENTAL E CLÍNICO.

Abstract

The present work describes the development of two photoelectrochemical biosensors for the detection of phenolic compounds. The first biosensor was used for the detection of epinephrine (EP) based on the modification of an indium tin oxide (ITO) surface with quantum dots of cadmium selenide/zinc sulphide core-shell quantum dots (CdSe/ZnS) and a protein, cytochrome c (Cyt c). The second sensor was used for detection of hydroquinone (HQ) by modifying a surface of fluorine doped tinoxide (FTO) with copper sulfide (CuS) and the enzyme horseradish peroxidase (HRP). The photosensors developed were named as CdSe/ZnS-Cytc/ITO and HRP-CuS-FTO. Both films were characterized by Electrochemical Impedance Spectroscopy. The photocurrent measurements were obtained by amperometry using a 30 W LED light bulb as the source of irradiation, that when the radiation is applied to the photosensor, it promotes the transfer of the electrons from the band of valence to the conduction band generating the pair electron/gap, species these that will promote the photocatalytic reactions. After optimization of the experimental parameters, the biosensors presented good responses for detection of the analytes, presenting a linear concentration range and detection limit of 1 x 10-6 mol L-1 to 1.2 x 10-3 mol L-1 and 2.0 x 10-9 mol L-1 for epinephrine, respectively, and 9.9 x 10- 9 mol L-1 to 6.32 x 10-3 mol L-1 and 9.3 x 10-10 mol L-1 for hydroquinone, respectively. The biosensors presented good recovery results for determination of EP in injectable drug samples (between 101.0 and 110.0 %) and for determination of HQ in water samples (99.0 and 102.2 %), suggesting a good accuracy for the proposed methods.