Magnetic-nanoparticle Conjugates and Methods of Use

Abstract

The present invention provides novel compositions of binding moiety-nanoparticle conjugates, aggregates of these conjugates, and novel methods of using these conjugates, and aggregates. The nanoparticles in these conjugates can be magnetic metal oxides, either monodisperse or polydisperse. Binding moieties can be, e.g., oligonucleotides, polypeptides, or polysaccharides. Oligonucleotide sequences are linked to either non-polymer surface functionalized metal oxides or with functionalized polymers associated with the metal oxides. The novel compositions can be used in assays for detecting target molecules, such as nucleic acids and proteins, in vitro or as magnetic resonance (MR) contrast agents to detect target molecules in living organisms.

1 . An aggregate comprising a plurality of conjugates, wherein each conjugate comprises a magnetic nanoparticle linked to a binding moiety that specifically binds to a target molecule, to another binding moiety, or to an aggregation inducing molecule, and wherein each conjugate within the aggregate is bound to at least one other conjugate in the aggregate through their respective binding moieties. 
     
     
         2 . The aggregate of  claim 1 , wherein the aggregate comprises 2 to 20 conjugates. 
     
     
         3 . The aggregate of  claim 1 , wherein the aggregate has a size of about 100 to 500 nm. 
     
     
         4 - 35 . (canceled) 
     
     
         36 . A conjugate comprising a magnetic nanoparticle linked to a first binding moiety, wherein the first binding moiety comprises a cleavage site for a target molecule and specifically binds to an aggregation inducing molecule, forms a cleavage site for the target molecule when the first binding moiety binds to a second binding moiety, or specifically binds to an aggregation inducing molecule that comprises a cleavage site. 
     
     
         37 . The conjugate of  claim 36 , wherein the first binding moiety comprises a polypeptide that comprises the cleavage site, and wherein the target molecule is an enzyme. 
     
     
         38 . The conjugate of  claim 36 , wherein the first binding moiety binds to a second binding moiety to form the cleavage site that is selectively cleaved by a target molecule, and wherein the target molecule is an enzyme. 
     
     
         39 - 73 . (canceled) 
     
     
         74 . A method for purifying a target molecule from a sample, the method comprising obtaining a conjugate comprising a nanoparticle comprising a magnetic metal oxide linked by a cleavable bond to a binding moiety that specifically binds to a binding site on the target molecule; obtaining a sample containing the target molecule in a fluid; mixing the conjugates with the sample under conditions sufficient to enable target molecules in the sample to bind to the binding moiety on the conjugate to form target molecule-binding moiety complexes; separating the conjugates from the sample; and cleaving the cleavable bond to separate the target molecule-binding moiety complexes from the conjugates, thereby purifying the target molecules. 
     
     
         75 . The method of  claim 74 , wherein the target molecule is a nucleic acid, and the binding moiety is an oligonucleotide that is complementary to a portion of the target nucleic acid. 
     
     
         76 . The method of  claim 74 , wherein the target molecule is a polypeptide, and the binding moiety is an antibody that specifically binds to a portion of the target polypeptide. 
     
     
         77 - 82 . (canceled)