RESUMO
This study presents a modified screen-printed carbon electrode (SPCE) to determine glucose in a custom-built flow injection system. The biosensor was constructed by immobilizing glucose oxidase on porous platinum nanoparticles decorated on multi-walled carbon nanotubes (GOx@PPtNPs@MWCTNs). The fabrication of the biosensor was completed by coating the GOx@PPtNPs@MWCTNs nanocomposite on an SPCE modified with a nanocomposite of poly(3,4-ethylenedioxythiophene) and Prussian blue (GOx@PPtNPs@MWCTNs/PEDOT@PB/SPCE). The fabricated electrode accurately measured hydrogen peroxide (H2O2), the byproduct of the GOx-catalyzed oxidation of glucose, and was then applied as a glucose biosensor. The glucose response was amperometrically determined from the PB-mediated reduction of H2O2 at an applied potential of -0.10 V in a flow injection system. Under optimal conditions, the developed biosensor produced a linear range from 2.50 µM to 1.250 mM, a limit of detection of 2.50 µM, operational stability over 500 sample injections, and good selectivity. The proposed biosensor determined glucose in human plasma samples, achieving recoveries and results that agreed with the hexokinase-spectrophotometric method (P > 0.05). Combining the proposed biosensor with the custom-built sample feed, a portable potentiostat and a smartphone, enabled on-site glucose monitoring.
Assuntos
Técnicas Biossensoriais , Compostos Bicíclicos Heterocíclicos com Pontes , Eletrodos , Análise de Injeção de Fluxo , Glucose Oxidase , Nanocompostos , Nanotubos de Carbono , Platina , Polímeros , Smartphone , Compostos Bicíclicos Heterocíclicos com Pontes/química , Polímeros/química , Nanocompostos/química , Glucose Oxidase/química , Técnicas Biossensoriais/métodos , Nanotubos de Carbono/química , Platina/química , Humanos , Glicemia/análise , Glucose/análise , Glucose/química , Técnicas Eletroquímicas/métodos , Peróxido de Hidrogênio/química , Ferrocianetos/química , Nanopartículas Metálicas/química , Enzimas Imobilizadas/química , Carbono/química , Limite de DetecçãoRESUMO
An enzymatic amperometric uric acid (UA) biosensor was successfully developed by modifying a screen-printed carbon electrode (SPCE) with Prussian blue-poly(3,4-ethylene dioxythiophene) polystyrene sulfonate composite (PB-PEDOT:PSS). The modified SPCE was coated with gold nanoparticles-graphene oxide-chitosan composite cryogel (AuNPs-GO-CS cry). Uricase (UOx) was directly immobilized via chemisorption on AuNPs. The nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, and Fourier transform infrared spectroscopy. The electrochemical characterization of the modified electrode was performed by cyclic voltammetry and electrochemical impedance spectroscopy. UA was determined using amperometric detection based on the reduction current of PB which was correlated with the amount of H2O2 produced during the enzymatic reaction. Under optimal conditions, the fabricated UA biosensor in a flow injection analysis (FIA) system produced a linear range from 5.0 to 300 µmol L-1 with a detection limit of 1.88 µmol L-1. The proposed sensor was stable for up to 221 cycles of detection and analysis was rapid (2 min), with good reproducibility (RSDs < 2.90 %, n = 6), negligible interferences, and recoveries from 94.0 ± 3.9 to 101.1 ± 2.6 %. The results of UA detection in blood plasma were in agreement with the enzymatic colorimetric method (P > 0.05).
Assuntos
Técnicas Biossensoriais , Criogéis , Eletrodos , Ouro , Grafite , Limite de Detecção , Nanopartículas Metálicas , Ácido Úrico , Técnicas Biossensoriais/métodos , Ácido Úrico/sangue , Ácido Úrico/análise , Ouro/química , Grafite/química , Criogéis/química , Nanopartículas Metálicas/química , Carbono/química , Polímeros/química , Porosidade , Análise de Injeção de Fluxo , Compostos Bicíclicos Heterocíclicos com Pontes/química , Quitosana/química , Poliestirenos/química , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Humanos , Urato Oxidase/química , Técnicas Eletroquímicas/métodos , Nanocompostos/química , Ferrocianetos/químicaRESUMO
A histamine biosensor was developed based on a screen-printed carbon electrode modified with Prussian blue (PB) electrodeposited on multi-walled carbon nanotubes covered with a macroporous layer of chitosan-gold nanoparticles composite cryogel (CS-AuNPs Cry). With its high specific surface area and conductivity, CS-AuNPs Cry proved an excellent supporting material for diamine oxidase (DAO) immobilization. PB acted as a redox mediator to promote electron transfer between hydrogen peroxide and the electrode surface. The PB reduction current was measured during the hydrogen peroxide-releasing oxidation of histamine catalyzed by DAO. The proposed biosensor displayed two linear ranges: 2.50-125.0 µmol L-1 and 125.0-400.0 µmol L-1. The limit of detection was 1.81 µmol L-1. Reproducibility was good (RSD = 5.46%), operational stability high, long-term stability excellent, and selectivity good. The biosensor determined histamine levels in fish and shrimps with satisfactory recoveries, and the obtained results agreed with those obtained by ELISA.