A novel gold nanoparticles decorated magnetic microbead-based molecular beacon for DNA multiplexing detection by flow...

Gold nanoparticles-based molecular beacon (Au NPs-MB), due to its extraordinary highly-quenching efficiency for fluorophores, has been extensively investigated and widely used for bioimaging and bioassay. However, apart from irreversible aggregation during the "aging" step, the preparation of Au NPs-MB often suffers from relatively poor salt stability, limiting its further in vivo application. Herein, Au NPs decorated magnetic microbeads was developed to construct a novel magnetic MB for DNA assay, which not only totally solved the aggregation problem of Au NPs, but also exhibited robust stability in buffer solution. Most importantly, the fluorescence signal of each microbeads could be collected individually, realizing single microbeads-based DNA imaging, and the detection limit for target DNA could reach 0.1 nM with the detection range of 0.2-20 nM. More importantly, because the magnetic microbeads with three sizes could be readily distinguished by flow cytometry, the employed three types of hairpin DNA probes can be labelled with the same dye FITC without fluorescence cross-interference. Therefore, multiplexing detection of tumor-suppressor genes (p16, p21 and p53) could be readily realized by using size-encoded magnetic microbeads pre-functionalized with corresponding probe DNA illustrating the potential of this method in multiplexing bioassay applications.