Nanoparticles having oligonucleotides attached thereto and uses therefor

A method of detecting a nucleic acid target having at least two portions comprising:

• providing nanoparticles having oligonucleotides attached thereto;
• providing one or more binding oligonucleotides, each of the binding oligonucleotides having two portions, the sequence of one portion being complementary to the sequence of at least two portions of the nucleic acid target and the sequence of the other portion being complementary to the sequence of the oligonucleotides on the nanoparticles;
• contacting the nanoparticles and the binding oligonucleotides under conditions effective to allow hybridization of the oligonucleotides on the nanoparticles with the binding oligonucleotides;
• contacting the nucleic acid target and the binding oligonucleotides under conditions effective to allow hybridization of the binding oligonucleotides with the nucleic acid target, wherein in the presence of said nucleic acid target and under hybridization conditions, the nanoparticles having oligonucleotides bound thereto form complexes with said nucleic acid target and binding oligonucleotides, the resulting nanoparticle-nucleic acid target complex having a sharp melting profile and an increased melting temperature, relative to a melting profile and a melting temperature of an analogous complex formed with said nucleic acid target, binding oligonucleotide, and unlabeled or fluorophore-labeled oligonucleotides having a sequence identical to the oligonucleotides bound to the nanoparticles, to allow for selective discrimination of a single nucleotide insertion, deletion, or mismatch in said nucleic acid target under stringent hybridization conditions, whereby the stringency of said hybridization conditions are higher than those possible for said analogous complex;
• and
• observing a detectable change.

A method of detecting a nucleic acid target having at least two portions comprising:

• contacting the nucleic acid target with at least two types of nanoparticles having oligonucleotides attached thereto;
• the oligonucleotides on the first type of nanoparticles having a sequence complementary to a first portion of the sequence of the nucleic acid target and being labeled with an energy donor;
• the oligonucleotides on the second type of particles having a sequence complementary to a second portion of the sequence of the nucleic acid target and being labeled with an energy acceptor;
• the contacting taking place under conditions effective to allow hybridization of the oligonucleotides on the particles with the nucleic acid target, wherein in the presence of said nucleic acid target, the nanoparticles having oligonucleotides bound thereto form a complex with said nucleic acid target, the resulting nanoparticle-nucleic acid target complex having a sharp melting profile and an increased melting temperature, relative to a melting profile and a melting temperature of an analogous complex formed with said nucleic acid target, and unlabeled or fluorophore-labeled oligonucleotides having a sequence identical to the oligonucleotides bound to the nanoparticles, to allow for selective discrimination of a single nucleotide insertion, deletion, or mismatch in said nucleic acid target under stringent hybridization conditions, whereby the stringency of said hybridization conditions are higher than those possible for said analogous complex;
• and
• observing a detectable change brought about by hybridization of the oligonucleotides on the particles with the nucleic acid target.