Bioelectrocatalytic detection of theophylline at theophylline oxidase electrodes

Research output: Contribution to journalArticle


Bioelectrocatalytic oxidation of theophylline was studied at gold and graphite electrodes modified with microbial theophylline oxidase (ThOx), a multi-cofactor redox enzyme capable of selective oxidation of theophylline. Gold electrodes were additionally modified with self-assembled monolayers (SAMs) of (-OH)- and (-NH2)-terminated alkanethiols of different chain lengths, to achieve compatibility between ThOx and the electrode surface. On graphite, ThOx was either physically co-adsorbed with a surfactant didodecyldimethylammonium bromide (DDAB), or entrapped within an Os-redox-polymer film. At all electrodes, ThOx was bioelectrocatalytically active; direct electrochemistry of ThOx in the absence of theophylline was followed only at the SAM-modified gold electrodes. Direct electrochemistry of ThOx correlated with redox transformations of the heme domain of ThOx, with a E-o/ of - 110 +/- 2 mV versus Ag vertical bar AgCl, at pH 7. Bioelectrocatalytic oxidation of theophylline was optimal at mixed (-OH)/(-NH2)-terminated SAMs; co-adsorption of ThOx with DDAB improved the bioelectrocatalytic performance of the ThOx-electrode. In both cases, the response to theophylline was within the mM range. Alternatively, a reagentless ThOx-electrode based on ThOx cross-linked within the Os-redox-polymer matrix demonstrated a linear response to theophylline within the physiologically important 0.02-0.6 mM (3.6-72 mg I-1) concentration range with a sensitivity of 52.1 +/- 7.8 mA cm(-2) m(-1). (c) 2006 Elsevier B.V. All rights reserved.


  • Elena E. Ferapontova
  • Stepan Shipovskov
  • Lo Gorton
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Analytical Chemistry


  • graphite, gold, alkanethiols, theophylline oxidase, bioelectrocatalysis, osmium-complex redox polymer
Original languageEnglish
Pages (from-to)2508-2515
JournalBiosensors & Bioelectronics
Issue number11
Publication statusPublished - 2007
Publication categoryResearch

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Analytical Chemistry (S/LTH) (011001004)