Label-free bifunctional electrochemiluminescence aptasensor for detection of adenosine and lysozyme

A label-free bifunctional electrochemiluminescence (ECL) aptasensor for parallel detection of small molecule (adenosine) and protein (lysozyme) was developed based on switching structures of aptamers from DNA/DNA duplex to DNA/target complex. Thiolated single-stranded DNA (DNA1) containing adenosine aptamer and sequence complementary to DNA2 was first immobilized on the Au electrode via sulfur-gold affinity. DNA2 containing lysozyme aptamer and sequence complememtary to DNA3 was bound to the electrode via forming DNA/DNA duplex. Gold nanoparticles functionalized with DNA3 (DNA3-GNP5) were used as signal amplifier to enhance the sensitivity of the aptasensor. With Ru(phen)(3)(2+) as the signal transducer, the aptasensor exhibited high sensitivity and specificity. Under optimal conditions, a linear range from 0.5 to 7 nM for adenosine (R=0.999) and from 0.5 to 9 ng/mL for lysozyme (R = 0.999) was obtained, respectively. The proposed method may provide a promising platform for ECL parallel detection of small molecules and protein. (C) 2012 Elsevier Ltd. All rights reserved.