| Autor: |
Otieno BA; Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States., Krause CE; Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.; Department of Chemistry, University of Hartford , West Hartford, Connecticut 06117, United States., Jones AL; Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States., Kremer RB; Department of Medicine, McGill University , Montreal, Quebec H3A 1A1, Canada., Rusling JF; Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.; Institute of Materials Science, University of Connecticut , Storrs, Connecticut 06269, United States.; Department of Surgery and Neag Cancer Center, University of Connecticut Health Center , Farmington, Connecticut 06232, United States.; School of Chemistry, National University of Ireland at Galway , Galway, Ireland. |
| Abstrakt: |
Parathyroid hormone-related peptide (PTHrP) is recognized as the major causative agent of humoral hypercalcemia of malignancy (HHM). The paraneoplastic PTHrP has also been implicated in tumor progression and metastasis of many human cancers. Conventional PTHrP detection methods like immunoradiometric assay (IRMA) lack the sensitivity required to measure target peptide levels prior to the development of hypercalcemia. In general, sensitive, multiplexed peptide measurement by immunoassay represents challenges that we address in this paper. We describe here the first ultrasensitive multiplexed peptide assay to measure intact PTHrP 1-173 as well as circulating N-terminal and C-terminal peptide fragments. This versatile approach should apply to almost any collection of peptides that are long enough to present binding sites for two antibodies. To target PTHrP, we employed a microfluidic immunoarray featuring a chamber for online capture of the peptides from serum onto magnetic beads decorated with massive numbers of peptide-specific antibodies and enzyme labels. Magnetic bead-peptide conjugates were then washed and sent to a detection chamber housing an antibody-modified 8-electrode array fabricated by inkjet printing of gold nanoparticles. Limits of detection (LODs) of 150 aM (∼1000-fold lower than IRMA) in 5 μL of serum were achieved for simultaneous detection of PTHrP isoforms and peptide fragments in 30 min. Good correlation for patient samples was found with IRMA (n = 57); r(2) = 0.99 assaying PTHrP 1-86 equiv fragments. Analysis by a receiver operating characteristic (ROC) plot gave an area under the curve of 0.96, 80-83% clinical sensitivity, and 96-100% clinical specificity. Results suggest that PTHrP1-173 isoform and its short C-terminal fragments are the predominant circulating forms of PTHrP. This new ultrasensitive, multiplexed assay for PTHrP and fragments is promising for clinical diagnosis, prognosis, and therapeutic monitoring from early to advanced stage cancer patients and to examine underlying mechanisms of PTHrP overproduction. |
