A sensitive enzyme biosensor for catecholics detection via the inner filter effect on fluorescence of CdTe quantum dots

In this paper, a new type of fluorescent biosensing system for catechol and 2,3-dihydroxybiphenyl (DHB) was described based on the inner filter effect (IFE), with the combination of CdTe quantum dots (QDs) and an extradiol dioxygenase, 2,3-dihydroxybiphenyl 1,2-dioxygenase (BphC). In the presence of BphC and its substrates, catechol and DHB, the excitation of QDs was partially weakened by the competitive absorption of the enzymatic reaction products, resulting in the quenching of QDs. The dependence of the emission intensity quenching on "quencher" concentration obeyed the quadratic equation, and the detection limits for catechol and DHB were 0.02 and 2 mu M, respectively. The present QD-BphC system also exhibited good selectivity to either catechol or DHB in the mixtures of other phenolic compounds. However, when catechol and DHB coexisted, the QD-BphC system could not separate the signals of these two compounds from each other due to the inherent substrate range of BphC. Nevertheless, the developed BphC-based fluorescent biosensor via the IFE on fluorescence of QDs could be employed as a robust support for the construction of other enzyme-based biosensors. (C) 2012 Elsevier B.V. All rights reserved.