Methods for detecting, isolation, and quantifying an analyte in a sample based on colloidal suspension of plasmonic metal nanoparticles

A method of diagnosing a condition characterized by an excess or a depletion of an analyte in a biological sample, the method comprising steps of:

• a) providing a colloidal suspension of nanoparticles of a plasmonic metal, the nanoparticles having attached on their surface a binding moiety for selective attachment of said analyte,
• b) adding the sample to the suspension, thus producing a mixture in which said analyte is attached to the nanoparticles in suspension,
• c) allowing sedimentation of the nanoparticles with bound analyte, thereby producing a sediment comprising the nanoparticles with bound analyte and a supernatant, and
• d) measuring the Localized Surface Plasmon Resonance (LSPR) spectrum of the supernatant,
• wherein the colloidal suspension comprises a known concentration of nanoparticles which can bind a known cut-off concentration of the analyte, wherein said cut-off concentration is between the average concentration of the analyte found in healthy subjects and the average concentration of the analyte found in subjects suffering from said condition,
• wherein the presence of a plasmonic metal band in the LSPR spectrum of the supernatant indicates that the sample had a concentration of the analyte lower than said cut-off concentration,
• wherein the presence of band associated with the analyte in the LSPR spectrum of the supernatant indicates that the sample had a concentration of the analyte higher than said cut-off concentration, and
• wherein the analyte is a biomolecule or a vesicle.

A method of isolating analyte from a sample, the method comprising the steps of:

• a) providing a colloidal suspension of nanoparticles of a plasmonic metal, the nanoparticles having attached on their surface a binding moiety for selective attachment of said analyte;
• b) adding the sample to the suspension, thus producing a mixture in which said analyte is attached to the nanoparticles in suspension;
• c) allowing sedimentation of the nanoparticles with bound analyte, thereby producing a sediment comprising the nanoparticles with bound analyte and a supernatant;
• d′) recovering the sediment,
• wherein the analyte is a biomolecule or a vesicle.

A method of detecting an analyte in a sample, the method comprising the steps of:

• a) providing a colloidal suspension of nanoparticles of a plasmonic metal, the nanoparticles having attached on their surface a binding moiety for selective attachment of said analyte;
• b) adding the sample to the suspension thus producing a mixture in which said analyte is attached to the nanoparticles in suspension;
• and
• c′) measuring the Localized Surface Plasmon Resonance (LSPR) spectrum of the mixture,
• wherein a shift in the position of the plasmonic metal band in the LSPR spectrum of the mixture compared to that of the suspension before addition of the sample indicates the presence of said analyte in the sample, and
• wherein the analyte is a biomolecule or a vesicle.