Label-free and sensitive electrogenerated chemiluminescence aptasensor for the determination of lysozyme

A novel label-free electrogenerated chemiluminescence (ECL) aptasensor for the determination of lysozyme is designed employing lysozyme binding aptamer (LBA) as molecular recognition element for lysozyme as a model analyte and Ru(bpy)(3)(2+) as an ECL signal compound. This ECL aptasensor was fabricated by self-assembling the thiolated LBA onto the surface of a gold electrode. Using this aptasensor, sensitive quantitative detection of lysozyme is realized on basis of the competition of lysozyme with Ru(bpy)(3)(2+) cation for the binding sites of LBA. In the presence of lysozyme, the aptamer sequence prefers to form the LBA-lysozyme complex, the less negative environment allows Ru(bpy)(3)(2+) cations to be less bound electrostatically to the LBAs on the electrode surface, in conjunction with the generation of a decreased ECL signal. The integrated ECL intensity versus the concentration of lysozyme was linear in the range from 6.4×10(-10) M to 6.4×10(-7) M. The detection limit was 1.2×10(-10) M. This work demonstrates that using the competition of target protein with an ECL signal compound Ru(bpy)(3)(2+) for binding sites of special aptamer confined on the electrode is promising approach for the design of label-free ECL aptasensors for the determination of proteins.