Chemiluminescent substrate delivery systems comprising a conjugate of a dendrimer and at least one chemiluminescent substrate are provided. The substrate delivery systems can also include a chemiluminescence enhancer. The dendrimer/chemiluminescent substrate conjugates can be used in kits including an enzyme capable of activating the chemiluminescent substrate to produce a peroxygenated intermediate that decomposes to produce light. The dendrimer/chemiluminescent substrate conjugates can be used in assays to detect the presence of an analyte (e.g., an enzyme, an antibody, an antigen or a nucleic acid) in a sample.