Biosensors find application in Bow analysis due to their high selectiv
ity and sensitivity. Decrease in the response during extended use, ori
ginated by degradation, inhibition or structural changes of the enzyme
or leaching of active components by the how, is the prevailing proble
m. As an alternative to additives and preparation techniques cited in
the literature, it is proposed to use DNA as a matrix for improving pr
eservation of the activity of a diphenol-sensor-based tyrosinase, Tyr,
(EC 1.14.18.1). The Tyr-DNA mixture was incorporated into carbon past
e, CP-DNA-Tyr, or applied on glassy carbon, GC-DNA-Tyr. The CP-DNA-Tyr
, covered by a membrane -of Cuprophan, presented superior performance
in amperometric operation under Bow conditions (electroreduction of th
e products of the enzymatic oxidation of diphenols in the presence of
O-2) In comparison with paste electrodes without DNA, CP-Tyr, a curren
t increase of one order of magnitude was observed for catechol FIA pea
ks, with good repeatability during several hours of operation. The res
ponse decayed ca. 50% after every 3 to 3 days of use (with dry storage
at 4 degrees C overnight). Original performance was recovered by simp
ly substituting the used paste for a new portion of stock paste, stabl
e for 2 months under refrigeration. Evaluation of 18 different substra
tes and potential interferents indicated that, at the adopted potentia
l of -0,15 V vs. Ag/AgCl, only p-cresol gives a response comparable to
catechol. Flow-injection determination of catechol samples was conduc
ted at a frequency of 30 injections/h, with linear response from the d
etection limit of 1x10(-6) up to 5x10(-5) mol l(-1). (C) 1998 Elsevier
Science B.V.