Magnetic nanocompositions for highly sensitive molecular and cellular enrichment, purification and detection

A method of capturing, enriching, purifying, detecting or measuring an analyte in a sample at a sub-nanogram level, comprising the steps of

• a) providing a nanocomposition comprising:
• a nanostructure having magnetic property, and an analyte-capturing member,
• wherein the nanostructure is operably linked to the analyte-capturing member,
• wherein the nanostructure comprises a nanoparticle and a low density porous 3-D structure, wherein the low density porous 3-D structure is made of organosilane, and has a density of <1.0 g/cc determined from dry mass of the 3-D structure divided by the total volume of such 3-D structure in an aqueous solution, wherein the nanoparticle is embedded in the low density porous 3-D structure,
• wherein the nanocomposition is capable of capturing an analyte at a concentration of no more than 1 nM, and the analyte is an antibody, a protein/peptide or a nucleic acid,
• b) contacting the sample with the nanocomposition to form a mixture solution and allowing the binding of the analyte with the nanocomposition,
• c) applying a magnetic field to the mixture, and
• d) evaluating the presence of or absence of the analyte.