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Isonostic™ Clinical Platform
Since it is often impossible to raise antibodies against specific isoforms, the TDI Isonostic™ Assay is based on separation of the isoforms enriched from the patient sample in the first step of an immunoassay. The enrichment process is conducted with monoclonal antibodies against the parent protein immobilized on magnetic beads or PhyTips™.1 The isoform separation and quantification is accomplished by capillary electrophoresis (CE), and is made possible with our proprietary dynamic coatings (EOTrol™ and UltraTrol™). Effectively, the CE instrument replaces a plate reader in the standard clinical laboratory workflow.
The first step of the TDI Isonostic™ assay is
an enrichment for the family of isoforms of
interest from the patient sample. This enrichment
step both pre-concentrates lower abundance proteins
(improving detection sensitivity) and provides
positive identification of the target antigen
(a regulatory necessity). The enriched antigen is
then eluted off the capture surface with a
volatile buffer system that is compatible with
the downstream isoform separation process. The
second step of the assay is the CE separation
and quantification of the enriched isoforms.
This step effectively replaces the substrate
incubation and plate reader detection steps of
a typical immunoassay.
The ability to robustly separate and quantify specific protein isoforms required two technology breakthroughs: 1) the development of an elution buffer system for the affinity capture step that was compatible with the down-stream separation process, and 2) elimination of protein losses in the separation process itself. Finally, the chosen solutions must support many different protein biomarkers. With our development of the proprietary EOTrol™ and UltraTrol™ dynamic coatings, TDI solved the two fundamental problems of capillary electrophoresis of proteins, electroosmotic flow uniformity and protein binding to the walls of the capillary, allowing TDI to take advantage of the generic CE platform for our Isonostic™ assay development.
