Electrochemical detection of thiols in biological media

The utilisation of catechol as an electrochemical indicator fur the presenc e of sulphydryl thiols (RSH) has been investigated. The electrochemical oxi dation of the catechol within tissue culture media was examined with the in fluence exerted on the redox chemistry by cysteine evaluated in terms of th e development of an analytical protocol. The electro-generation of o-quinon e was found to be followed by a 1,4-addition reaction with available cystei ne such that an increase in the current, attributed to the re-oxidation of the thiol-catechol adduct, could be exploited as means of quantifying the c oncentration of the thiol. The selectivity of the reaction has been assesse d with no interference from lysine, tyrosine, methionine or cystine. Other amino acids possessing sulphydryl thiol functionalities (homocysteine and g lutathione) were, however, found to react through a similar route to that o bserved with cysteine. (C) 2001 Elsevier Science B.V. All rights reserved.