Desenvolvimento de biossensores utilizando nanotubos de carbono e nanopartículas de ouro

Abstract

First, a glassy carbon electrode modified with functionalized carbon nanotubes (CNTs) and glucose oxidase was proposed. Cyclic voltammetry of GOx immobilized onto the surface of CNTs showed a pair of well-defined redox peaks, which corresponds to the direct electron transfer of GOx, with a formal potential of -0.418 V in 0.1 mol L-1 phosphate buffer solution (pH 7.0). An apparent heterogeneous electron transfer rate constant of 1.69 s-1 was obtained. The determination of glucose was carried out by square wave voltammetry and the developed biosensor showed good reproducibility and stability. The second biosensor was a boron-doped diamond electrode modified with AuNPs electrodeposited and Tyrosinase (Tyr). The occurrence of direct electron transfer between the electrode surface and the Tyr active site was verified by cyclic voltammetry, yielding the following parameter values: formal redox potential of 0.115 V. The developed Tyr-AuNPs/BDD biosensor exhibits good sensitivity, stability, and reproducibility for the determination of phenol by SWV. The third proposed biosensor was developed based on acetylcholinesterase, gold nanoparticles and poly (allylamine hydrochloride) film on the surface of screen printed carbon electrodes (SPCE) for the determination of pesticides using a portable micromachined flow injection system. The AChE-AuNPs/SPCE biosensor presented a limit of detection of 5.0 x 10-8 mol L-1 for Diuron. In addition, the biosensor showed good sensitivity, stability and reproducibility for Diuron determination in water samples. Finally, a novel electrochemical immunosensor using electrodeposited gold nanoparticles modified-screen-printed carbon electrodes (AuNPs/SPCEs) was developed for the determination of prolactin.The variables involved in the preparation of the immunosensor and the electrochemical detection step were optimized, which presented a limit of detection of 10 ng mL-1. The analytical usefulness of the immnunosensor for the analysis of real samples was demonstrated by analyzing human serum spiked with PRL at two different concentration levels.