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

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

• a) providing a nanocomposition comprising:
• a nanostructure having magnetic property, and a cell-capturing member,
• wherein the nanostructure is operably linked to the cell-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 the cell at a sub-nanogram level, wherein the sub-nanogram level is a concentration of no more than 400,000 cells/ml, 100,000 cells/ml, 100 cells/ml, 20 cells/ml or 4 cells/ml,
• b) contacting the sample with the nanocomposition to form a mixture solution and allowing the binding of the cell with the nanocomposition,
• c) applying a magnetic field to the mixture, and
• d) evaluating the presence of or absence of the cell.