Au nanorods-TiO2 photonic crystal plasmonic-photonic hybrid sensor for label-free detection and identification of DNA molecules with single nucleotide polymorphisms

Abstract

Highly sensitive optical sensors for label-free detection of DNA must have high usability and wide applicability for achieving advances in the medical and biological science fields. However, current sensors do not simultaneously satisfy these criteria. Here, we developed a simple, cost-effective, and sensitive plasmonic–photonic hybrid sensor using gold nanorods as nanoantennae and a photonic crystal slab (PCS) as a microcavity. In this report, we performed simple microscopic detection and identification of DNA molecules with Alzheimer’s disease-associated single nucleotide polymorphisms, which is an important indicator for early diagnosis. The PCS was fabricated using nanoimprint lithography; the gold nanorods were controllably coupled with the PCS. The device sensitivity was experimentally assessed by controlling the plasmonic–photonic coupling resonance, which was enabled by tuning the PCS-coupled AuNR amounts. The sensitivity was also investigated by theoretical modeling of the hybrid sensor, based on the temporal coupled mode theory (TCMT). The TCMT-based theoretical model well explained the experimental results. In a demonstration of ultrasensitive detection of DNA, the identification of single nucleotide mismatched DNA molecules (~1 pM) and detection of several DNA molecules (~1000), with a limit of detection of 5.9 aM, were successfully achieved. This sensor may thus have wide applications for DNA analysis.