Colloidal Au-Enhanced Surface Plasmon Resonance for Ultrasensitive Detection of DNA Hybridization

TLDR

The large angle shifts achieved with particle‑amplified SPR enable imaging of DNA arrays. This study introduces a nanoparticle‑amplified SPR method for ultrasensitive DNA hybridization detection. The amplified SPR signal arises from increased surface mass, the high dielectric constant of Au nanoparticles, and electromagnetic coupling with the Au film, as confirmed by DNA melting and digestion experiments. Au nanoparticle tags produce over a 10‑fold angle shift and more than a 1000‑fold sensitivity gain, enabling a ~10 pM limit of quantitation on 4 × 4 DNA arrays that rivals fluorescence methods and demonstrates the promise of particle‑amplified SPR for ultrasensitive array‑based DNA detection.

Abstract

A new approach to ultrasensitive detection of DNA hybridization based on nanoparticle-amplified surface plasmon resonance (SPR) is described. Use of the Au nanoparticle tags leads to a greater than 10-fold increase in angle shift, corresponding to a more than 1000-fold improvement in sensitivity for the target oligonucleotide as compared to the unamplified binding event. This enhanced shift in SPR reflectivity is a combined result of greatly increased surface mass, high dielectric constant of Au particles, and electromagnetic coupling between Au nanoparticles and the Au film. DNA melting and digestion experiments further supported the feasibility of this approach in DNA hybridization studies. The extremely large angle shifts observed in particle-amplified SPR make it possible to conduct SPR imaging experiments on DNA arrays. In the present work, macroscopic 4 × 4 arrays were employed, and a ∼10 pM limit of quantitation was achieved for 24-mer oligonucleotides (surface density ≤8 × 108 molecules/cm2). Even without further optimization, the sensitivity of this technique begins to approach that of traditional fluorescence-based methods for DNA hybridization. These results illustrate the potential of particle-amplified SPR for array-based DNA analysis and ultrasensitive detection of oligonucleotides.