Mass tag analysis for rare cells and cell free molecules
The invention generally relates to mass tag analysis for rare cells and cell free molecules. In certain embodiments, the invention provides an apparatus including an essentially non-absorbent membrane having at least one pore, a microwell operably associated with the essentially non-absorbent membrane, and an electric field generator. The apparatus may be configured such that an electric field produced by the electric field generator operably interacts with a sample in the microwell and expels a droplet of the sample through the at least one pore in the essentially non-absorbent membrane. In certain embodiments, apparatuses of the invention are used for detection, and optionally quantification, of a target analyte from a heterogeneous sample, such as a rare target analyte (e.g., rare cell) from a biological sample.
1 . A method for detecting a target analyte from a heterogeneous sample, the method comprising:
providing an apparatus that includes an essentially non-absorbent membrane comprising at least one pore, a microwell operably associated with the membrane, and an electric field generator operably associated with the membrane; wherein the microwell comprises a back wall, side walls, and a front that is operably associated with the essentially non-absorbent membrane, wherein the back wall, the side walls, and the front define a volume within the microwell; and wherein the electric field generator is physically separate and spaced apart from the back wall and side walls of the microwell and positioned within a space behind the back wall of the microwell and aligned within the space to not be outside of the side walls of the microwell such that the electric field generator inductively imparts an electric field to a sample within the volume within the microwell defined by the back wall, the side walls, and, and the front of the microwell to operably interact with the sample in the volume within the microwell and expel a droplet of the sample through the at least one pore in the essentially non-absorbent membrane;
introducing a heterogeneous sample to at least the membrane;
introducing to the sample a plurality of affinity agents that each comprise a first molecule, wherein the plurality of affinity agents specifically bind the target analyte in the sample;
removing unbound affinity agents;
introducing one or more additional molecules to the sample, wherein the one or more additional molecules interact with the first molecule to form a mass spectrometry label;
providing voltage to the sample via the electric field generator to release a droplet through the at least one pore, wherein the droplet comprises a portion of the sample and the mass spectrometry label; and
analyzing the droplet for presence of the mass spectrometry label, wherein the presence of the mass spectrometry label indicates presence of the target analyte in the sample.
2 . The method according to claim 1 , wherein the first molecule is a mass spectrometry label precursor.
3 . The method according to claim 2 , wherein the one or more additional molecules is an alteration agent that interacts with the mass spectrometry label precursor to form the mass spectrometry label.
4 . The method according to claim 1 , wherein the affinity agent is a particulate.
5 . The method according to claim 1 , wherein the target analyte is a rare cell and the heterogeneous sample is a heterogeneous biological sample.
6 . The method according to claim 1 , further comprising quantifying the target analyte in the sample by quantifying an amount of mass spectrometry label analyzed.