Electrochemical detection of theophylline based on the redox reaction of silver ions captured onto the abasic site-incorporated duplex DNA

Abstract

We have successfully developed a novel, label-free, electrochemical sensing system for detection of theophylline. In our new system, an abasic site-incorporated duplex DNA immobilized on the surface of gold electrode is employed as a key component to analyze theophylline with electrochemical read-out. The abasic site opposite cytosine in duplex DNA plays an important role as a binding pocket for both silver ion and theophylline. This sensor is operated with the electrochemical signal generated by redox reaction of silver ions captured onto cytosine groups opposite the abasic site in duplex DNA. This phenomenon is regulated by the competitive binding of theophylline on the same site in duplex DNA. When theophylline is absent, silver ions are adsorbed onto cytosine groups opposite the abasic site in duplex DNA leading to the highly elevated electrochemical signal. On the other hand, theophylline present in the solution binds to the abasic site by pseudo base pairing with the cytosine nucleobase, which consequently inhibits binding of silver ion to the abasic site. As a result, redox reaction of silver ion does not occur, which results in the significantly decreased electrochemical signal. By applying this new electrochemical strategy, theophylline was detected with the high selectivity over structurally similar substances such as caffeine and theobromine. Finally, theophylline in human blood serum was successfully analyzed, verifying the diagnostic capability of this method.