Use of IgY antibodies and semiconductor nanocrystal detection in cancer biomarker quantitation

Biomarkers play a pivotal role in the early detection and diagnosis of cancer. Accurate quantitation of certain biomarkers is crucial to reach correct treatment decisions. In practice, immunohistochemistry (IHC) remains the most important diagnostic technique to evaluate protein biomarker expression in tissue biopsies. However, IHC has largely been qualitative. Low specificity of the mammalian IgG antibodies used to capture the analytes and instability of fluorescence from the organic dyes used as the detecting agents are among the major factors that have impeded the development of quantitative IHC. Avian IgY antibodies have many attractive biochemical, immunological and production advantages over IgGs and are, therefore, better substitutes in diagnostic applications. Using IgY in immunoassays can potentially eliminate false positives and often results in low background and interference. Quantum dots (QDs) have recently emerged as a novel class of fluorophores, promising for many biomedical imaging applications. Fluorescence from QDs is significantly brighter and more photostable than organic dyes. In addition, QDs offer the capacity of multiplexed detection of several biomarkers simultaneously. Combining the high sensitivity and specificity of IgY antibodies and the high brightness and photostability of QDs in IHC has been demonstrated to improve biomarker detection and quantitation.