Multi-functional crosslinked Au nanoaggregates for the amplified optical DNA detection.

We report a novel sandwich type assay for the optical detection of DNA using multi-component crosslinked Au nanoparticle aggregates. In this design, a DNA bridged multi-functional Au nanoparticle aggregate, which integrates DNA recognition (detection probe), signal amplification (enzyme, horseradish peroxidase) and non-specific blocking (bovine serum albumin, BSA) section, is employed as detection probe. The sandwich type assay includes the capture probe that immobilized on magnetic microparticles, target and the Au nanoparticle aggregates detection probe. In a typical sensing process, the Au aggregates detection probe is brought to the proximity of magnetic particles through the DNA hybridization. Once magnetic field is added, these sandwich complexes are magnetically separated. As a result, HRP that confined at the surface of Au aggregates could catalyze the enzyme substrate and generate an optical signal. This assay is employed for the detection of breast cancer-associated BRCA-1 gene. The detection limit is about 1 fmol, which is significantly improved as compared with the results obtained from individual Au nanoparticle labeled assay. Thus, our results address the possibility of Au nanoaggregates as platform for DNA detection.