Density-based separation of biological analytes using multiphase systems

A method of analyzing a sample comprising at least one analyte of interest using a multi-phase system, comprising:

• a) providing a sample comprising at least one analyte of interest;
• b) providing a multi-phase system comprising two or more phases with clear boundaries, wherein
• at least one of the phases comprises a phase component, wherein the phase component is selected from the group consisting of a polymer, a surfactant, and combinations thereof;
• each of the two or more phases has a different density and the two or more phases, taken together, represent a density gradient;
• and
• the phases are phase-separated from each other;
• and
• c) introducing the sample comprising a mixture of a tag molecule and the analyte to the multi-phase system, wherein the analyte and the tag molecule form a tag molecule-analyte adduct;
• and
• d) allowing the tag molecule-analyte adduct to migrate to a location in the multiphase system that is characteristic of its density, wherein during migration the sample contacts one or more of the two or more phases sequentially and the analyte and the tag molecule-analyte adduct occupy different locations.

A kit for separating a sample comprising one or more biological analytes of interest using a multi-phase system comprising:

• a) two or more phase components selected from the group consisting of a polymer, a surfactant, and combinations thereof;
• b) optionally a tag molecule capable of binding the one or more biological analytes of interest, wherein the tag molecule has a different density than the biological analyte of interest;
• and
• c) instructions for:
• (i) combining the two or more phase-separated solutions with a common solvent to create a multi-phase system;
• (ii) optionally, combining the biological analyte of interest and tag molecule, and
• (iii) separating the biological analyte of interest from the sample.