Evanescent field biosensor using polymer slab waveguide-based cartridges for the optical detection of nanoparticles

We present a polymer optical waveguide integration technology for the detection of nanoparticles in an evanescent field (EF)-based biosensor. Polymer waveguides together with their light coupling structures are designed to be integrated in a novel cartridge concept which will eventually lead to cost-effective, rapid, and easy-to-use point-of-care testing (POCT). The selected slab waveguides generate a homogeneous and well-defined EF, illuminating magnetic nanoparticles that are used as optical contrast labels and are measured using dark-field microscopy. The nanoparticles quantitatively bind to the sensor surface in the presence of target molecules, mediated by antibodies. Compatibility of the waveguide materials with these biomolecules is therefore a strong requirement. When designing a biosensor for POCT, it is also necessary to consider fabrication and manipulation tolerances, targeting the compatibility with mass-production technologies. In this context, polymer optics offer unique advantages, and in combination with the optical contrast labels a very high sensitivity can be achieved. The sensing concept was assessed by comparing various commercially available polymer materials (LightLink, Ormocer, Epocore/Epoclad) in terms of waveguide design and fabrication, optical performance (detection of nanoparticles), and biological compatibility and performance as a sensor surface in an immuno-assay for cardiac troponin I.