The Radioimmunoassay and Biomarkers Core offers a large number of high quality immunoassay and biochemistry services to basic, translational, and clinical investigators performing diabetes, obesity and related metabolic disease research. The RIA/Biomarkers Core is housed within the Institute for Diabetes, Obesity & Metabolism (IDOM) located on the 12th floor of the Smilow Center for Translational Research (room 12-183). This location places the Core on the same floor and in close proximity to the Islet Cell Biology Core, Functional Genomics Core, and Rodent Metabolic Phenotyping Core that enhances the already close interactions among these DRC Scientific Cores.

IDOM is also home to the Metabolic Tracer Resource directed by Dr. John Millar which offers gas chromatography-mass spectrometry (GC-MS) services for the analysis of stable isotope tracers, and so provides a “one-stop” shop for DRC investigators requiring metabolic assays of hormone and metabolite levels as well as, metabolite fluxes derived from human, animal, and cell culture experiments. The integrated delivery of assay services provided by the RIA/Biomarkers Core is further enhanced by informatics infrastructure for ordering, tracking, billing and delivery of service using iLab, a cross-Unuversity site for sample submission. The performance of a large number of immunoassay services in a central core facility rather than in scattered locations throughout the University provides a significant overall savings in equipment, personnel effort, and supplies for investigators, while importantly allowing for the generation of results with superior quality due to our enhanced quality control/quality assurance/quality management (QA/QC/QM) processes.

Core Functions

Approximately 170 different diabetes, obesity and metabolism-related biomarkers can be assayed, and the number of assay services offered continues to expand. Current services include radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), and multiplex ELISA on the Luminex MAGPIX platform, multiplex ELISA on the ELLA platform, high performance liquid chromatography (HPLC) on the ThermoFisher platform, and metabolite assays on the Yellow Springs Instruments (YSI) platform for an expanding variety of diabetes and metabolism related hormones and cytokines derived from blood, urine, salivary and tissue samples.

Samples generated for assay in the DRC Islet Cell Biology, Rodent Metabolic Phenotyping Cores are delivered directly to the RIA/Biomarker Core for analysis, ensuring proper collection, handling, reporting, and interpretation of data generated from the DRC Scientific Cores.

The DRC RIA/Biomarkers Core has an established relationship with the NIDDK-sponsored Chronic Renal Insufficiency Cohort (CRIC) Study central laboratory located on the 1st floor of the Smilow Center that provides access to biochemical autoanalyzer services for DRC investigators.


RIA services at Penn are unique to the RIA/Biomarkers Core and offer high-volume, rapid turnaround of affordably priced insulin, C-peptide, proinsulin and glucagon assays for human and rodent blood and tissue samples. RIA services are also established for measuring pancreatic polypeptide, somatostatin, and cAMP.

ELISA services are also available to assay insulin from low sample volume mouse studies, and for non-human primate studies to assay monkey insulin and C-peptide.

Gastrointestinal hormones and adipokines including ghrelin, PYY, leptin, and adiponectin are routinely measured by RIA, while others such as GLP-1, GIP, IL-6, and TNF-α are routinely measured by ELISA.

Multiplex ELISA services are available on the Luminex MAGPIX platform which uses cell-sorting technology to measure multiple proteins simultaneously on magnetic bead based immunoassays. This technology can be particularly useful to investigators studying mouse models and those with repeated sampling human protocols, where sample volumes are often low.

In all cases, we use commercial kits and commercial quality control material from suppliers that focus on endocrinology research requirements (e.g. Millipore, R&D Systems, Mercodia, ALPCO, etc.). In order to minimize cost, insulin, C-peptide, proinsulin and glucagon are grouped in batches and processed within two weeks. Other hormones are processed within two weeks of kit arrival, with the exception of catecholamines that are measured by HPLC. All immunoassays and metabolite assays are run in duplicate (and for some ELLA assays in triplicate) with both intra- and inter-assay coefficients of variation (c.v.) standardly assessed as part of our QC/QA/QM processes.

Most frequently assayed hormones and biomarkers:







GIP, total





GLP-1, active & total











Growth hormone














DPP4 mass & activity










PP, pancreatic polypeptide; cAMP, cyclic adenosine monophosphate; GIP, glucose-dependent insulinotropic polypeptide; GLP, glucagon-like peptide; PYY, peptide tyrosine tyrosine; DPP4, dipeptidylpeptidase-4; FGF-21, fibroblast growth factor-21; ACTH, adrenocorticotropic hormone; CBG, corticosteroid binding globulin; IGF-1, insulin-like growth factor-1; SHBG, sex hormone binding globulin; FSH, follicle stimulating hormone; LH, luteinizing hormone; T4, thyroxine; T3, triiodothyronine; TSH, thyroid stimulating hormone; TNF, tumor necrosis factor; IL, interleukin; hsCRP, high sensitivity C-reactive protein.


The RIA/Biomarkers Core director, Dr. Michael Rickels, and technical director, Dr. Heather Collins, advise investigators on determining the best assay method, proper collection strategy, and the costs involved to address their scientific question. This consultation starts at the time of preparation of research grants to assist investigators with appropriately budgeting for assay costs, as well as the supplies and reagents necessary for the proper collection of samples for particular assays. In order to measure multiple analytes with small sample volumes, multiplexing of ELISAs by Luminex or ELLA is often required. New assays are implemented as needed. Using the information discussed during the consultation, investigators will receive a quote that includes the assays, the sample volume required, the additives needed and the pricing information so that investigators can accurately budget these items when applying for grant funding. Certain additives such as protease inhibitors for protection of islet and gastrointestinal hormone peptides can be prepared by the Core for use by investigators with an additional charge.

Training and Education

The RIA/Biomarkers Core is dedicated to providing outreach and training for the DRC research community in order to support the highest standard of biomarker research for diabetes, obesity and related metabolic disorders. As part of the education and training function of the core, Drs. Collins and Rickels meet with investigators, coordinators and nurses to train them on the procedures for collecting samples for reliable measurement, including the addition of chemicals and/or proteases as may be required for the protection of intact peptide hormones. Where study subjects are evaluated cross-sectionally or prospectively before and after intervention, samples are batched with representation across groups and with longitudinal samples from the same subjects assayed simultaneously to minimize inter-assay variation from affecting effect sizes. Thus, collection and storage conditions for samples are critical and the Core provides necessary supplies and standard operating procedures (SOPs) to investigators and their teams to ensure optimal practice. As Director of the Translational Research Program for IDOM, and Associate Director of the Penn Center for Human Phenomic Science (CHPS), Dr. Rickels supervises clinical research and nursing staff who contribute to investigator training and facilitate the implementation of appropriate sample collection and processing procedures in the CHPS units where the clinical and translational research studies in diabetes and obesity are conducted.