LABEL-FREE OPTICAL BIOSENSOR FOR EARLY DIAGNOSIS OF PANCREATIC CANCER

Anterior gradient-2 (AGR2) is a secreted protein, associated with a wide range of human cancers. In pancreatic cancer patients, AGR2 levels were found to be elevated in pancreatic juice at a precursor stage of malignant cancer, which is an ideal stage for diagnosis. Thus, AGR2 is a promising pancreatic cancer biomarker that could be used for the early detection of this deadly disease. Our work aims to design a label-free biosensing platform for the detection of AGR2 in pancreatic juice. The biosensor is based on a nanostructured porous silicon (PSi) optical transducer, conjugated with aptamers. Nucleic-acid aptamers have emerged in recent years as promising recognition elements, presenting diverse advantages in comparison to traditional antibodies. Herein, DNA aptamers specifically targeting the AGR2 protein are utilized. Oxidized PSi Fabry-Pérot thin films are synthesized and functionalized to immobilize the amino-terminated aptamers via a standard coupling chemistry. The aptamers immobilization is confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, Refractive Interferometric Fourier Transform Spectroscopy (RIFTS) and fluorescent labeling. Introduction of AGR2 protein to the aptamer-modified PSi induces changes in the reflectivity spectrum, thus enabling simple, rapid and real-time detection of the protein, utilizing RIFTS method. Furthermore, the specific aptamer-AGR2 interaction facilitates the high selectivity of this biosensor, with no binding of other biologically abundant proteins.