One dimensional photonic crystal for label-free and fluorescence sensing application

Abstract

The development of more sensitive and more reliable sensors aids medical applications in many fields as diseases detection or therapy progress. This thesis threats the development of an optical biosensor based on electromagnetic modes propagating at the interface between a finite one-dimensional photonic crystal (1DPC) and a homogeneous external medium, also named Bloch Surface Waves (BSW). BSW have emerged as an attractive approach for label-free sensing in plasmon-like sensor configurations. Besides label-free operation, the large field enhancement and the absence of quenching allow the use of BSW to excite fluorescent labels that are in proximity of the 1DPC surface. This approach was adapted to the case of angularly resolved resonance detection, thus giving rise to a combined label-free/labelled biosensor platform. BSW present many degrees of design freedomthat enable tuning of resonance properties. In order to obtain a figure of merit for an optimization, I investigated the measurement uncertainty depending on resonance width and depth with different numericalmodels. This has led to a limit of detection that can assist the choice of the best design to use. Two tumor biomarkers, such as vascular endothelial growth factor (VEGF) and Angiopoietin-2 (Ang2), have been considered to be detected with the BSW biosensing platform. For this purpose the specific antibodies for the two tumor biomarkers were immobilized on the 1DPC biochip surface. The conclusive experiments reported in this work demonstrated the successful detection of the VEGF biomarker in complex matrices, such as cell culture supernatants and human plasma samples. Moreover, the platformwas used to determinate Ang2 concentration in untreated human plasma samples using low volumes, 300 μL, and with short turnaround times, 30 minutes. This is the first BSW based biosensor assay for the determination of tumor biomarker in human plasma samples at clinically relevant concentrations.