Label-free specific detection of immunoglobulin G antibody using nanoporous hydrogel photonic crystals

Photonic crystal (PC) based biosensors have been given attention because of their obvious advantages such as sensitivity, simple and low-cost realization. Many kinds of PC based biosensors have been reported, for example, holographic PCs, porous silicon PCs, PC fibers and colloidal crystal film. Among these PC based sensors, we have interested on an inverse opal structure film in order to apply to specific and label-free detection of proteins. This label-free PC bioassay is more attractive than labeling detection because target molecules can be detected in their nature forms, truly portable point-of-care testing is possible, and quantitative measurement of molecule interaction is allowable. In this study, we propose a specific and label-free detection method for immunoglobulin G (IgG) antibody using nanoporous hydrogel photonic crystals with simple process and cost-effective way. The hydrogels used as a backbone of PC in this study, which provide rather homogeneous water surrounding, are ideal substrates for biomolecular screening. Also, three-dimensional hydrogel structures show high capacity for biomolecule immobilization, greater probability of interacting with the target ligand, high S/N, and sensitivity. Finally, the film type biosensor was fabricated using photo-curable hydrogels with colloidal templating methods. The reflective color of the fabricated sample is changed from green to dark orange with the bandgap shift of 50 nm, when the IgG concentration was 10 mg/ml. Furthermore, our device showed different bandgap shifts according to the level of antibody concentration, so that it can be used to measure quantitative molecular interactions. This designed label free detection system has great potential for next generation of bioassay platform for diagnosis of pathogens such as virus, bacteria, and fungi. (C) 2012 Elsevier B.V. All rights reserved.