e12502 Background: Her2Neu (H) antigen, expressed on 20% of Breast cancers, is an established target for antibody therapy with T. Immunohistochemistry is still the most widely used technique to detect h level which is time consuming and does not reveal any details of interaction between the molecules. We have developed a new innovative biosensor based novel technique to study real time interaction of h antigens with T using QCM Piezo-immunosensor. This quantitative label free peptide based assay can be used to characterize cell surface antigen, to study antigen- antibody interactions and obtain understanding of mechanisms of resistance. Methods: A label free and reagent free peptide mimotope capacitive biosensor is developed for T quantification based on non-Faradaic readout. The low sensitivity issue of capacitive biosensor was overcome with two innovations: peptide mimotope mixed SAM biointerface and dilution of the testing buffer. Signal amplification was achieved through dilution of the PBS buffer to tune Cdl to dominate the overall capacitance change upon target binding. After 1000 times dilution, limit of detection is lowered 500 times (0.22 µg/mL) and the sensitivity increased 20 times (0.04192 (µg/mL)-1). Results: Binding was very specific. Signal amplification strategy is practical. Further applied to planar electrode for optimizing sensing, response time in less than 1 minute. Conclusions: This is the first report of T detection using electrochemical method based on non-Faradaic impedance. h antigen density and interactions of antigens will help physicians to determine the clinical efficacy and resistance mechanisms to targeted antibodies like T and ado-Trastuzumab.For the first time, we have established a low cost, highly sensitive, fast, synthetic, QCM assay which could be used as a basis for developing a new generation of affinity-based Immunosensor assays. This real time capability and its simplicity of operation are highly suitable for multipurpose studies on living cells including cell immobilization, cytotoxicity of drugs, and the cell action mechanisms