RESUMO
A new type of pH biosensor was developed for biological applications. This biosensor was fabricated using silicon microsystem technology and consists in two platinum microelectrodes. The first microelectrode was coated by an electrosynthesized polymer and acted as the pH sensitive electrode when the second one was coated by a silver layer and was used as the reference electrode. Then, this potentiometric pH miniaturized biosensor based on electrosynthesized polypyrrole or electrosynthesized linear polyethylenimine films was tested. The potentiometric responses appeared reversible and linear to pH changes in the range from pH 4 to 9. More, the responses were fast (less than 1 min for all sensors), they were stable in time since PPy/PEI films were stable during more than 30 days, and no interference was observed. The influence of the polymer thickness was also studied.
Assuntos
Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Elétrons , Etilenodiaminas/síntese química , Polietilenoimina/síntese química , Eletroquímica , Etilenodiaminas/química , Concentração de Íons de Hidrogênio , Lactonas , Microscopia de Força Atômica , Oxirredução , Polietilenoimina/química , Polímeros/química , Pirróis/química , Prata , Fatores de TempoRESUMO
The development of a new electrochemical sensor consisting in a glass-sealed metal microelectrode coated by a polyethylenimine film is described. The use of polymers as the entrapping matrix for enzymes fulfils all the requirements expected for these materials without damaging the biological material. Since enzyme immobilization plays a fundamental role in the performance characteristics of enzymatic biosensors, we have tested four different protocols for enzyme immobilization to determine the most reliable one. Thus the characteristics of the potentiometric biosensors assembled were studied and compared and it appeared that the immobilization method leading to the most efficient biosensors was the one consisting in a physical adsorption followed by reticulation with dilute aqueous glutaraldehyde solutions. Indeed, the glutaraldehyde immobilized urease sensor provides many advantages, compared to the other types of sensors, since this type of urea biosensor exhibits short response times (15-30s), sigmoidal responses for the urea concentration working range from 1 x 10(-2.5) to 1 x 10(-1.5) M and a lifetime of 4 weeks.
Assuntos
Técnicas Biossensoriais/instrumentação , Eletroquímica/instrumentação , Polietilenoimina/química , Urato Oxidase/química , Ureia/análise , Ureia/química , Adsorção , Técnicas Biossensoriais/métodos , Eletroquímica/métodos , Enzimas Imobilizadas/química , Desenho de Equipamento , Análise de Falha de Equipamento , Microeletrodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Propriedades de SuperfícieRESUMO
Potentiometric pH sensors based on linear polyethylenimine (L-PEI) and linear polypropylenimine(L-PPI), two synthetic enzymes and biocompatible polymers, films were prepared by electropolymerization of three different monomers: ethylenediamine (EDA), 1,3-diaminopropane (1,3-DAP) and diethylenetriamine (DETA) in order to be used in clinical, dermatological and biological applications, such as in vivo analysis. In a first step a biosensor was tested which consisted in a platinum wire protruded from glass sheath. The polymer film coated on these platinum electrodes showed good linear potentiometric responses to pH changes from pH 3 to 10. Resulting electrodes present both good reversibility and good stability versus time. The effect of the different polymer film thicknesses to potentiometric responses was also studied. This study allowed us to develop a miniaturized pH biosensor in the second step. This sensor was fabricated using photo-lithography, followed by sputtering and lift-off processes, and it included an electronic detection system. We have also successfully studied the potentiometric responses to pH changes of this device over a period of 1 month, and so we propose this new pH micro-biosensor as an alternative to classical pH sensors currently used in dermatology.
Assuntos
Materiais Biocompatíveis/química , Técnicas Biossensoriais/instrumentação , Eletroquímica/instrumentação , Eletrodos , Concentração de Íons de Hidrogênio , Polietilenoimina/química , Polipropilenos/química , Materiais Biocompatíveis/síntese química , Técnicas Biossensoriais/métodos , Eletroquímica/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Miniaturização , Polímeros/síntese química , Polímeros/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Propriedades de SuperfícieRESUMO
Potentiometric biosensors based on butyrylcholinesterase are developed by co-reticulation of the enzyme with glutaraldehyde on an electropolymerized polyethyleneimine film at the electrode surface. The BuChE-electrode was tested as biochemical sensor for detection of an organophosphorus pesticide, trichlorfon in liquid, the detection being based on the enzyme inhibition. The enzyme electrode showed a detection limit for trichlorfon below 10(-7) M.
