Silicon nanoparticles as a luminescent label to DNA.

We successfully conjugated 1-2 nm diameter silicon nanoparticles to a 5'-amino-modified oligonucleotide (60mer) that contains a C6 linker between amide and phosphate groups. The conjugation was implemented via two photoinduced reactions followed by a DNA labeling step through formation of a carboxamide bond. Photoluminescence of the conjugates is dominated by two blue bands (400 and 450 nm maximal) under 340 nm excitation. The quantum yield of oligonucleotide-conjugated nanoparticles was determined to be 0.08 as measured against quinine sulfate in 0.1 M HClO(4) as a reference standard. We report a conjugation process that allows labeling of Si nanoparticles to an oligonucleotide in aqueous solutions. Ways to further optimize the procedure in order to achieve narrower and brighter photoluminescence are discussed.