A DISPOSABLE BIOSENSOR FOR ACRYLAMIDE DETERMINATION
a a a b
Nelson A. F. Silva , Manuel J. Matos , Amin Karmali , Maria Manuela Rocha
a
CIEQB-ISEL – Chemical Engineering and Biotechnology Research Center, Portugal
b
DQB-FCUL – Chemistry and Biochemistry Department, Portugal
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 ºC and 220 ºC. 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 μL of whole cell suspension and 10 μL of glutaraldehyde 2.5 % (v/v) is deposited. This
mixture is incubated overnight, at 4ºC, allowing an adequate immobilization of Pseudomonas aeruginosa
cells.
Electric contacts Electric contacts
Figure 1. Electric circuits for measuring conductivity and resistivity changes
The transduction process is based on conductivity or resistivity changes in the sensitive zone due to the
+
increasing of NH4 amount, according to the following reaction:
-
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.
[1] A. Stobiecka, H. Radecka, J. Radecki, Biosens. Bioelectron. 22 (2007) 2165-2170.
[2] N. Silva, D. Gil, A. Karmali, M. Matos, Biocatal. Biotransf. 27(2) (2009) 143-151.