Direct detection of disease biomarkers in clinical specimens using cationic nanoparticle-based assays and versatile and green methods for synthesis of anisotropic silver nanostructures

A method for capturing at least one biological material of interest comprising contacting a sample comprising said material with silica nanoparticles, which comprise a ligand for the biological material, for a time and under conditions sufficient for the material to bind to the silica nanoparticles and eluting or recovering the biological material from the silica nanoparticles;

• wherein said method further comprises contacting the eluted or recovered biological material with silver nanoparticles;
• wherein said at least one biological material is HCV RNA,
• wherein the ligand for the biological material comprises a nucleic acid complementary to the HCV RNA, and
• wherein said contacting comprises
• contacting the HCV RNA with silica nanoparticles conjugated to a nucleic acid complementary to HCV RNA,
• removing material that is not bound to the silica nanoparticles,
• eluting HCV RNA bound to the silica nanoparticles,
• contacting the eluted HCV RNA with cationic silver nanoparticles, and
• detecting HCV RNA when the cationic silver nanoparticles aggregate, wherein aggregation of cationic silver nanoparticles is determined colorimetrically by color change from yellow which denotes substantially non aggregated nanoparticles to colorless or to white which denotes aggregated nanoparticles.

A method for detecting a target molecule comprising:

• contacting a sample suspected of containing the target molecule with silica or magnetic nanoparticles that are bound to a capture probe or capture ligand for said target molecule,
• separating the silica or magnetic nanoparticles and any target molecule bound to the capture probe or capture ligand from other components of the sample,
• separating captured target molecule from the silica or magnetic nanoparticles,
• contacting said separated target molecule with positively charged silver nanoparticles that are not bound to capture probes or capture ligands, and
• selecting a sample containing the target molecule when the silver nanoparticles aggregate in comparison with a control sample that does not contain the target molecule to be detected;
• wherein the target molecule is a protein,
• wherein the silica or magnetic particles are bound to a capture ligand for the protein, and
• wherein nanoparticle aggregation is determined colorimetrically by a color change from yellow which denotes substantially nonaggregated silver nanoparticles, to colorless or to white which denotes aggregated silver nanoparticles.