Avaliação da imobilização da urease em membranas de quitosana para aplicação em biossensor amperiométrico de ureia.

Abstract

With the upward development of new technologies, demand for new sensing systems is increasing because there is a need for better accuracy in the results of biological analyzes, with low cost and in real time, before that, the biosensors are devices capable of provide that kind of result. Diseases related to renal insufficiency require such precision and rapidity, which is characterized by the concentration of urea in blood or urine, thus eliminating a series of laboratory procedures. Therefore, for assembling a urea biosensor is needed a selective and specific bio-component that can identify the urea without any interference, as in the case of the enzyme. The enzyme capable of catalyzing the hydrolysis of urea is urease, forming a reaction product of carbon dioxide and ammonia. To be used in a biosensor, the enzyme must be immobilized, as this way confer greater operational stability and a longer storage thereof. This immobilization can be performed by means of polymers. Chitosan is a natural polymer that become increasingly more important for this application, on its properties such as low cost, abundance in nature, easy processing capacity of membrane formation, among others. Given the above, the objective of this work is to immobilize the enzyme urease as a matrix using chitosan and chitosan / glutaraldehyde, evaluating different conditions of preparation of membranes. Membranes were deposited on a transducer used as a support of stainless steel strips, electrodeposited with antimony. Soon after, characterizations were performed by optical microscopy (OM) and scanning electron microscopy (SEM) to evaluate the surfaces of the membranes. Also, the bioresponse electrode tests were performed to evaluate the effectiveness of the immobilized enzyme, through sensitivity responses, selectivity, stability, response time, linearity range, specificity and reproducibility of biosensors. It was observed that the immobilized enzyme with chitosan and crosslinking addition of glutaraldehyde gave the best responses with more operational stability and increased storage of the enzyme, thereby improving the lifetime thereof.