Characterization of drivers for on-analyzer stability of immunoassays using specified reagents as a marker

Team Masters Projects 2007-2008

April 30, 2008

TMP Sponsor: Ortho-Clinical Diagnostics Company Advisors: Michael Fiske

Consulting Scientist:
                            Tanya Ferguson

Ortho-Clinical diagnostics (OCD) is a Johnson & Johnson company known for its clinical chemistry, immunodiagnostics, immunohematology and blood screening products and services. OCD has reported less than optimal on-analyzer stability profiles for some of their Enzyme Multiplied Immunoassay Technique (EMIT) assays, in particular Valproic Acid (VALP). The current work-around wastes company supplies and money. Therefore, the OCD Team Masters Project at KGI has been charged with further investigating the cause of this phenomenon, and has focused primarily on the enzyme-conjugate used in the assays. Several avenues to improve reagent on-analyzer stability were explored by implementing wet lab techniques, engineering devices, and Design of Experiments (DOE) methodology.

The team developed several methods for isolating and characterizing the enzyme-conjugate when it is aged on the analyzer. They compared the aged enzyme-conjugate to its native state using SDS-PAGE, Western Blots, and Size Exclusion Chromatography. A temperature gradient in the reagent storage carousel was characterized and a small device was subsequently built to replicate the gradient. Finally, using DOE studies, the addition of excipients to help mitigate the observed instability was examined. The team's studies have increased knowledge of the biophysical properties of the enzyme-conjugate and the VALP assay, which may lead to more cost effective solutions for EMIT assays.