Desenvolvimento de biossensor eletroquímico com imobilização da urease em membranas poliméricas.

Abstract

Biosensors are analytical devices able to identify specific substances qualitatively and / or quantitatively, used in various applications, which have been improved over the years. These analytical devices have a broad-based economic growth, especially of diagnostics and point of care devices because of its fast, accurate answers in determining diseases, variations of substances in the human body that may be harmful or not to health. Urea is one of these substances in the human body and increased blood urea ratio occurs in acute or chronic renal failure, congestive heart failure, severe dehydration, increased protein catabolism, muscle loss. Some medications can also cause increases in urea. Despite the numerous patents, articles, dissertations and theses, research in the development of biosensors for urea rate monitoring are still present today. These observations prompted us to study and develop a biosensor for urea detection. To this and were studied: the preparation of the electrode in stainless steel ribbon with electrodeposition antimony, modification of the crystalline phase formed and immobilizing the urease enzyme in polymer membranes of chitosan and cellulose acetate on the electrode. They characterized by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) and evaluation of biosensor properties: sensitivity, linearity, period of stability, selectivity, reproducibility and repeatability. The images obtained by OM show that the condition of the electrodeposition coating changes the surface of stainless steel strips with decreasing defects with heat treatment there is a surface modification of electrodes. The images obtained by SEM also show a roughened, porous surface in which there is a growth of different forms of structures. The XRD results show that the electrodeposition condition affects the formation of crystallite size and heat treatment modifies the crystal phase formed in electrodeposition. The images obtained by OM of chitosan and cellulose acetate membranes with and without enzyme urease have a uniform surface without morphological changes. The SEM showed that the polymer membrane overlying pictures electrodes, however, the chitosan membranes formed thicker layers. The results of sensitivity, linearity and stability period showed that all biosensors are sensitive to concentrations of urea and showed linearity range where answers are best, the period of stability was less than 2 minutes in most cases. The selectivity results show that the biosensors are selective and suffer minimal changes in the presence of creatinine. In the reproducibility, it was found that the biosensors are reproducible with minimal variation in bioresponse. The repeatability results show that the biosensor begin to undergo variation in results with few measurements. The results indicate that both chitosan and cellulose acetate membranes are viable for enzyme immobilization and modification of the metal oxide with antimony for the heat treatment used in the electrodes of the biosensor significantly improves the biosensor properties.