In various embodiments methods are provided for identifying and/or quantifying one or more antigens of interest (biomarkers) on the surface of cell- or tissue-specific exosomes. In an illustrative embodiments the methods comprise: i) incubating a population of exosomes with one or more tissue-specific antibodies that bind an antigen specific to a tissue or cell type of interest that produces exosomes, where the tissue specific antibodies are attached to acceptor bead or magnetic beads so the antibodies bind exosomes displaying the antigen; ii) obtaining a purified population of exosomes bound by the tissue specific antibodies with and/or without photocleavable linker based technology; iii) incubating a test subset of the isolated tissue-specific exosomes with acceptor beads attached to test antibodies that bind an antigen of interest thereby binding exosomes that display the antigen of interest and a control subset with negative control acceptor beads; v) incubating the test subset of isolated exosomes and the control subset of exosomes with a donor-bearing antibody that binds an exosome specific antigen; and vi) detecting a signal produced upon illumination of the control subset and/or the test; and vii) detecting the antigen(s) of interest.