Abstract: A method for using bodily fluids in determining the cell-specific potency of drugs is provided. A composition comprising a plurality of types of carriers, wherein each carrier comprises a single-cell lethal amount of a therapeutic agent and a unique barcode identifying that agent and wherein the composition comprises equal numbers of each carrier type, equal concentrations of the agent and equal concentrations of each barcode is also provided. Further, methods useful for studying the therapeutic profile of one or more drugs within a cell microenvironment, including but not limited to a tumor, are provided.