Acrylamide is chemical compound with potentially hazardous effects on human health and environment.
In April 2002, the Swedish National Food Agency, presented some data indicating the presence of acrylamide in fried, baked and deep-fried food and later also in coffee. In fact, acrylamide can be formed when certain types of food, containing significant amounts of reducing sugars (like glucose) and amino acids (like asparagine), are cooked at temperatures between 90 ¨¬C and 220 ¨¬C. According to the International Agency for research on Cancer (IARC), acrylamide is, since 1994, considered as probably carcinogenic to humans [1]. Presently, and according to the World Health Organization (WHO), acrylamide in food is considered to be a worldwide issue of major concern.
The present work reports the results concerning the development of several electrochemical biosensors for acrylamide determination, based on a direct biochemical interaction between acrylamide and intact bacterial cells. The biological recognition element consisted of whole cells of Pseudomonas aeruginosa containing intracellular amidase activity, which catalyses the hydrolysis of acrylamide producing ammonium ion (NH4+) and acrylic acid. The first transduction process used was potentiometric and consisted of an ammonium ion selective electrode. Whole cells were immobilized in several types of polymeric membranes, such as polyethersulphone, nylon and polycarbonate, which were, then, attached to the surface of the selective electrode [2]. Studies were carried out in order to investigate other immobilization procedures, bearing in mind the development of alternative devices. Encapsulation matrices, such as gelatine or agarose, cross-linking agents, such as glutaraldehyde or BSA and sol-gel based films, were some of the reagents and materials used in this investigation.
Presently our group is developing new disposable devices as an alternative to the use of ammonium ion selective electrodes. These devices consist on electric circuits (fig. 1) with a sensitive zone where a mixture of 50 ¥ìL of whole cell suspension and 10 ¥ìL of glutaraldehyde 2.5 % (v/v) is deposited. This mixture is incubated overnight, at 4¨¬C, allowing an adequate immobilization of Pseudomonas aeruginosa cells.
On the other hand, pH changes are also detectable, since the concentration of hydroxide ion (OH-) increases as the reaction proceeds. In fact, the biochemical signal transduction can also be accomplished by measuring pH changes on the sensitive area of the electric circuit. The analytical performance of these biosensing devices is being investigated, considering some figures of merit such as linear response, detection limit, sensitivity, response time and half life time.