Gold nanoparticles-coated polystyrene beads for the multiplex detection of viral DNA

We report on the preparation of a sensing platform for the fast multiplex detection of short oligonucleotide sequences. Monodispersed micro-sized polystyrene beads (average diameter of ca. 4.72 μm) were prepared and subsequently coated with nanosized gold nanoparticles. The micro-sized beads are large enough to scatter light and allow the detection of specific analytes using flow cytometry. Fluorescently labeled DNA hairpins are assembled onto the gold nanoparticles. In the absence of the target sequence, the metal particles quench the probe signal. Upon hybridization, the fluorescent signal of the hairpin is turned on and is readily detected by the flow cytometer with a detection limit of 5 nM. The sensing platform was able to sense and discriminate in parallel two specific genetic markers of Vaccinia virus and hepatitis B virus. Viral sequences spiked in an artificial serum were readily detected with comparable sensitivity to the buffer solution. The assay time was optimized from the assembly to testing to take less than 2 h including a hybridization of 30 min.