Abstract 735: Photonic crystal microarray sensing of biomolecules: Detection of ZEB1 associated with the epithelial-mesenchymal transition in lung cancer cells.
Authors: Chakravarty Swapnajit , Lai Wei-Cheng , Zou Yi , Drabkin Harry A. , Simon George R. , Chin Steve H. , Chen Ray T. , Gemmill Robert M. 
Published: August 2014

Abstract
We experimentally demonstrate the ability of Photonic Crystal microcavity-based biosensors to specifically detect the EMT transcription factor, ZEB1, in minute volumes of sample. Two-dimensional Photonic Crystals manufactured from silicon-on-insulator (SOI) have recently demonstrated the ability to confine and guide slow light on length scales of the wavelength of light. This has led to high sensitivity as well as miniaturization into compact sensors for chemical and bio-sensing. The precise wavelength of infrared light trapped by the resonance cavity of a Photonic Crystal is influenced in a very sensitive fashion by binding interactions between biomolecules attached to the silicon surface. In essence, the binding interaction alters the refractive index of the resonance cavity and this is detected as a shift in the resonance wavelength trapped by the device. When the sensor surface is derivatized with a specific antibody, the binding of the corresponding antigen will generate a resonance shift, revealing the presence of the antigen even when the antigen is present as a minor component in a complex whole-cell lysate. The resonance shift is detected directly and does not require any secondary labeling. The sensor cavity used here is dimensionally comparable to a mitochondrion, having a surface area of ∼5-10 μm2 which contacts approximately 13 nL of sample. The device was able to reliably detect ZEB1 binding in diluted samples of NCI-H358 non-small cell lung cancer cells containing ∼10 cells/μL. Specificity was demonstrated using a sandwich assay in which a second antibody was introduced following the initial binding and washing steps. The resonance wavelength was then super-shifted, but only when the second reagent applied was a different ZEB1-specific antibody that recognized a distinct epitope. These Photonic Crystal waveguides can be multiplexed on a single chip yielding a useful platform for highly sensitive and rapid detection of several biomolecules simultaneously in minute samples. Moreover, the sandwich assay principle can be applied to interrogate post-translational modifications of the captured proteins, so long as site-specific antibodies are available. The Photonic Crystal biosensor should be applicable to biomarker detection in minute biopsies, monitoring of pathway activation states in small samples, and detection of fusion or mutant proteins in hematological malignancies and solid tumors.
Citation Format: Swapnajit Chakravarty, Wei-Cheng Lai, Yi Zou, Harry A. Drabkin, George R. Simon, Steve H. Chin, Ray T. Chen, Robert M. Gemmill. Photonic crystal microarray sensing of biomolecules: Detection of ZEB1 associated with the epithelial-mesenchymal transition in lung cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 735. doi:10.1158/1538-7445.AM2013-735