Electrochemiluminescence biobarcode method based on cysteamine--gold nanoparticle conjugates.

The recently developed DNA-gold nanoparticle (DNA-GNP) biobarcode assay provides polymerase chain reaction (PCR)-like sensitivity for nucleic acid and protein targets without a need for enzymatic amplification. However, application of the conventional assay is challenged by its complex, expensive, time-consuming, and labor-intense procedure. Herein, we present a new electrochemiluminescence (ECL) biobarcode method based on cysteamine-GNP conjugates. In this strategy, an ECL nanoprobe is fabricated that relies on GNP that is modified with tris-(2,2'-bipyridyl) ruthenium (TBR) labeled cysteamine to boost ECL signals and single strand DNA for target recognition. Specifically, a sandwich complex that consists of a biotin labeled capture probe, target DNA, and cysteamine-GNP conjugate is captured by magnetic microparticles (MMPs) and subsequently identified by the ECL signals from loaded TBR. With the use of the developed probe, a limit of detection as low as 100 fM can be achieved and the assay exhibits excellent selectivity for single-mismatched DNA detection even in human serum. The proposed ECL based method should have wide applications in diagnosis of genetic diseases due to its high sensitivity, simplicity, and low cost.