Grating-coupled surface-plasmon fluorescence DNA sensor

Genetic analysis is considered to be the ultimate diagnostic approach in many fields, e.g., in medicine for disease detection, in agricultural technology for food and feed authentication, in forensics, to name a few. Consequently, great interest is growing in developing sensitive and reliable analytical tools (biosensors) to identify whole DNA sequences, oligonucleotide fragments, or single-nucleotide polymorphisms (SNPs). In addition, these biosensors are becoming vital tools for clinical diagnosis and point-of-care systems. They need to be of high sensitivity, high specificity, fast response, inexpensive, and easy to use. In this work, we discuss a surface-plasmon fluorescence grating coupler-based biosensor, fabricated on polymer substrates, and with a designed surface binding procedure that offers the direct response required for a sensor to be implemented in a disposable system. These gratings fabricated on polymer substrates using an embossing technique showed excellent and reproducible resonance coupling results. We also present a monitoring protocol for hybridization reactions based on fluorescence resonance energy transfer (FRET) to quench the bulk solution contribution that decreases the sensitivity of the grating biosensors.