Sensitive detection of proteins using difunctional DNA-gold nanoparticles

The use of D2-Au for the highly sensitive detection of proteins by specifically taking advantage of the two independently addressable oligonucleotide moieties of D2-Au was investigated. A 12 mer coding sequence of the oligomer 2 of D2-Au 1 was employed to specifically bind additional layers of gold nanoparticles by using the difunctional nanoparticles, in combination with appropriate linker oligonucleotides to enhance binding signals and macroscopic read-out. Antibody-functionalized nanoparticles D-Au6 were used as regeants in an immunoassay, to demonstrate the functionality of the two different DNA binding sites of difunctional AuNPs. To increase the read-out signal of the immunoassay, the self-assembly of multiple layers of particles were used. The signal intensities obtained dependent on the amount of antigen present, indicated that the detection of surface-bound antigen through IgG labeled gold nanoparticles occurred specifically.