Desenvolvimento de biossensor eletroquímico para detecção de lactato

Abstract

The development of new sensory platforms is of great interest to the field of biosensors, especially those with low cost and high reproducibility characteristics. In this context, the present study aimed at the production and characterization of a biosensor platform composed of films produced by the physical adsorption selfassembly technique (Layer-by-Layer - LbL) using chitosan and AuNps@PTS (gold nanoparticles stabilized with PTS polymer – a sulphonated polythiophene derivative). Subsequently, the platform formed was used for immobilization of the enzyme lactate oxidase (LOx) and detection of lactate. The films were formed in different numbers of bilayers and characterized by spectroscopic measurements of ultraviolet absorption (UV-Vis) and fluorescence, and electrochemical measurements. The LOx enzyme was immobilized on two LbL film bilayers through dripping and subsequent crosslinking performed with the addition of glutaraldehyde. The detection of lactate was performed through cyclic voltammetry (VC) measurements on standard samples. The results show that film growth was relatively homogeneous, and until the fourth bilayer the absorption intensity increased linearly with the number of bilayers. CV measurements showed that the electrode modified with two film bilayers allows greater charge transfer, being the platform chosen for immobilization of the LOx enxima and detection of lactic acid. Voltammograms showed that the presence of the LOx enzyme hinders charge transfer and that its immobilization was effective. Detection measurements show that the developed platform is suitable for detecting lactate, and the analytical signal presented a linear regime between the increase in the anodic current magnitude and the increase in the lactate concentration, in the range of 0.5 to 30 mM of lactate. The platform used was able to detect human sweat lactate at different times and intensities of physical exercise, with detection limits close to those found in the literature.