Detection of an Ovarian Cancer Biomarker Using Biotinylated Single-Chain Fv with a Surface Plasmon Resonance Sensor

Travis M. Quarles, Jon Ladd, Allen D. Taylor, and Shaoyi Jiang. Chemical Engineering, University of Washington, Benson Hall/Box 351750, Seattle, WA 98195

A custom built surface plasmon resonance (SPR) sensor was used to sensitively detect an ovarian cancer biomarker. Collaborators at the Fred Hutchinson Cancer Research Center (FHCRC) have developed biotinylated single-chain Fv (scFv) specific to HE4 boimarker. The biotinylated scFv were immobilized on a streptavidin surface, and detection curves and limits of detection for HE4 were determined. The protein of interest, HE4, is a biomarker for ovarian cancer patients identified by researchers at the FHCRC. ScFv antibody fragments have become very popular in immunological research due to their decreased cost and time of production, their retention of activity and specificity, and their smaller size when compared to whole antibodies. ScFv can be more densely bound on a surface and can therefore give higher sensitivities in SPR sensors. The mixed self-assembled monolayer of oligoethylene glycol alkanethiols and biotinylated alkanethiols provides a nonfouling background capable of streptavidin binding. Detection of HE4 has also been achieved in blood sera from cancer patients. We have developed an arrayed sensor with SPR imaging that has the ability to do high-throughput analysis without losing sensitivity. An automated microarrayer is used to spot proteins onto the SPR sensor surface, and the imaging system is capable of monitoring ~1000 spots. This sensor has applications in biomarker recognition and discovery, and in the profiling and screening of patient blood serum samples.