Label-Free Detection of Tumor Angiogenesis Biomarker Angiopoietin 2 Using Bloch Surface Waves on One Dimensional Photonic Crystals

We describe the design and fabrication of biochips based on 1-D photonic crystals supporting Bloch surfacewaves for label-free optical biosensing. The optical properties of Bloch sur- face waves are studied in relation to the geometry of the photonic crystals and on the properties of the dielectric materials used for the fabrication. The planar stacks of the biochips are composed of silica, tantala, and titania that were deposited using plasma-ion- assisted evaporation under high-vacuum conditions. The biochip surfaces were functionalized by silanization, and appropriate flu- idic cells were designed to operate in an automated platform. An angularly resolved ellipsometric optical sensing apparatus was as- sembled to carry out the sensing studies. The angular operation is obtained by a focused laser beam at a fixed wavelength and de- tection of the angular reflectance spectrum by means of an array detector. The results of the experimental characterization of the physical properties of the fabricated biochips showthat their char- acteristics, in terms of sensitivity and figure of merit, match those expected from the numerical simulations. Practical application of the sensor was demonstrated by detecting a specific glycoprotein, Angio-poietin 2, that is involved in angiogenesis and inflammation processes. The protocol used for the label-free detection of An- giopoietin 2 is described, and the results of an exemplary assay.