Large-Scale Nanogrooved Photonic Crystals for Label-Free Biosensing by Guided-Mode Resonance.

We have developed large-scale one-dimensional photonic crystals from standard recordable Blu-ray disks, tailored to sense unlabeled biorecognition events on their surface. These materials rely on coating, with layers of 80 nm of titanium oxide, nanogrooved polycarbonate plates obtained from regular disks. As a result, they present guided-mode resonances that we have demonstrated that can be exploited to quantify biorecognition events by means of the bandgap positions in the transmission spectra. These photonic crystals have displayed well-correlated dose-response curves in immunoassays to quantify IgGs, C-reactive protein, and lactate dehydrogenase. The detection limit reached is 16 ng/mL, 2µg/mL, and 18 ng/mL, respectively. Herein we describe the experimental procedures and methods to fabricate and functionalize these photonic crystals, perform immunoassays on them, set up an optical system to measure their response, and process the resulting data to perform bioanalytical determinations in label-free format.

Disk-based one-dimensional photonic crystal slabs for label-free immunosensing.

One-dimensional photonic crystal slabs are periodic optical nanostructures that produce guided-mode resonance. They couple part of the incident light into the waveguide generating bandgaps in the transmittance spectrum, whose position is sensitive to refractive index variations on their surface. In this study, we present one-dimensional photonic crystal slab biosensors based on the internal nanogrooved structure of Blu-ray disks for label-free immunosensing. We demonstrated that this polycarbonate structure coated with a critical thickness of TiO2 generates guided-mode resonance. Its optical behavior was established comparing it with other compact disk structures. The results were theoretically calculated and experimentally demonstrated, all them being in agreement. The bioanalytical performance of these photonic crystals was experimentally demonstrated in a model assay to quantify IgGs as well as in two immunoassays to determine the biomarkers C-reactive protein and lactate dehydrogenase (detection limits of 0.1, 87, and 13 nM, respectively). The results are promising towards the development of new low-cost, portable, and label-free optical biosensors that join these photonic crystals with dedicated bioanalytical scanners based on compact disk drives.