DNA Origami‐Guided Assembly of Gold Nanoparticles for Plasmonic Enhancement in Fiber Optic Surface Plasmon Resonance Sensing

Surface plasmon resonance (SPR) biosensors, including fiber-optic SPR (FO-SPR), are powerful tools for biomolecular detection; however, their sensitivity and limits of detection can be further enhanced through innovative signal amplification strategies. One such challenge is the limitation of single gold nanoparticle (AuNP) signal amplification, which can constrain the sensitivity of these systems. In this study, programmable DNA origami is introduced as a platform to precisely position AuNPs within a single nanostructure, enabling systematic control over both the number and spatial arrangement of AuNPs, as well as the surface attachment point. A linear increase in signal amplification with the number of AuNPs is observed, which transitions into a nonlinear enhancement when the resonance wavelengths of the AuNPs and the underlying gold film are aligned by adjusting the film thickness. In this case, plasmonic coupling dominates, driving the nonlinear effect in signal enhancement. By combining these strategies, a twofold improvement in the limit of detection for a single-stranded DNA target is achieved. This highlights the effectiveness of arranging multiple signal-enhancing units on a single construct for FO-SPR biosensing, providing a versatile and modular platform that may be extended to other surface-sensitive optical technologies, facilitating the design of bioassays with significantly improved sensitivity.