Síntese verde de nanopartículas metálicas: potenciais aplicações na construção de sensores eletroquímicos

Abstract

Two electrodes were developed based on the modification of carbon paste with metallic nanoparticles synthesized by green synthetic routes. The first one is a glassy carbon paste electrode (GCPE) modified with gold nanoparticles (AuNPs) stabilized in pineapple gum (Ananas comosus; PG). This electrode was applied in the determination of Promethazine Hydrochloride (PMZ). The second electrode developed was a graphite paste electrode modified with silver nanoparticles (AgNPs) synthesized using (GAR) extract. In both syntheses, the natural extracts used (PG and GAR) simultaneously acted as a reducing and stabilizing agents for the formed nanoparticles. The UV-VIS spectroscopy characterization of the nanoparticles revealed an absorption band at 524 and 407 nm for AuNPs-PG and AgNPs-GAR, respectively. TEM analysis showed mean particle diameters of 10.33 ± 1.6 nm for AuNPs-PG and 9.2 ± 1.5 nm for AgNPs-GAR. The electrochemical characterization of GCPE/AuNPs-PG and CPE/AgNPs-GAR, carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in precense of Fe(CN)6 3-/4- probe, showed that obtained nanoparticles conferred to the electrodes higher current values and a lower charge transfer resistance (Rct). GCPE/AuNPs-PG was applied to determine PMZ, which by VC was oxidized in two stages, with two anodic processes at approximately 0.75 and 0.48 V and a cathodic process at approximately 0.40 V. For the determination of PMZ, the square wave voltammetry (SWV) technique was used. The SWV parameters were optimized by means of a Box-Behnken factorial design with triplicate at the central point and the obtained values were a = 90 mV, f = 100 Hz and ΔEs = 8 mV. ANOVA showed that the variance explained is very close to the maximum explainable variance (Rsqr = 0.9999; Radj = 0.999) and the lack of adjustment was not significant. The GCPE/AuNPs-PG showed linear response in the range of 3.98 to 15.7 μmol L-1 of PMZ, with detection and quantification limits equal to 1.09 and 3.62 μmol L-1, respectively. The GCPE/AuNPs-PG was applied for the quantification of PMZ in commercial pharmaceutical formulations, obtaining recovery percentages between 94.89 to 97.30%, with RDS values below 5.0%. The hemocompatibility of the obtained AuNPs-PG were evaluated by cytotoxicity and osmotic fragility assays in human leukocytes and erythrocytes and the nanomaterial synthesized in the present work did not exhibit toxic effects towards the referred cells. CPE/AgNPs-GAR was applied to determine 5-FU. By VC, it was found that the antitumor agent 5-Fluororacil (5-FU) was irreversibly oxidized at 1.13 V on the surface of the CPE/AgNPs-GAR according to a pH dependent and diffusion-controlled mechanism. The pH of the BR buffer for the determination of 5-FU was optimized by SWV, with a maximum current at pH 8.0 being observed. The SWV parameters optimized through a Box-Behnken factorial design with triplicate at the central point were a = 80 mV, f = 85 Hz and ΔEs = 17 mV. ANOVA showed that the variance explained is very close to the maximum explainable variance (Rsqr = 0.9896; Radj = 0.9818) and the lack of adjustment was not significant. The CPE/AgNPs-GAR showed a linear response in the range of 30 to 300.0 μmol L-1 of 5-FU, with detection and quantification limits equal to 0.76 and 2.53 μmol L-1, respectively. The modified electrode was applied for the quantification of 5-FU in commercial injectable pharmaceutical formulation, with an average recovery percentage equal to 99.83 with relative standard deviation within acceptable limits (0.11%).