Sensitive Oligonucleotide Detection Using Resonant Coupling between Fano Resonance and Image Dipoles of Gold Nanoparticles

Abstract

The surface plasmon resonance (SPR)-based sensor has been widely used for biodetection. One of the attractive roles is the gold nanostructure with Fano resonance. Its sharp resonant profile takes advantage of the high figure of merit (FoM) in high-sensitivity detection. However, it is still difficult to detect small molecules at low concentrations due to the extremely low refractive index changes on the metallic surface. We propose using the coupling of image dipoles of gold nanoparticles (AuNPs) and Fano resonance of periodic capped gold nanoslits (CGNs) for sensitive small-molecule detections. The coupling mechanism was verified by three-dimensional finite-difference timedomain calculations and experiments. AuNPs on CGN form image dimer assemblies and induce image dipole with resonance wavelengths ranging from 730 to 550 nm. The surface plasmon polaritons (SPPs) interact with the image dipole of the AuNP on the CGNs and then scatter out through the periodic gold caps. The experimental results show that the peak intensity of grating resonance is decreased by the effect of image dipole and exhibits the maximum intensity change when the Fano resonance matches the resonance of image dipole. The 50 nm AuNPs can be detected with a surface density of less than one particle/μm 2 by using the intensity change as the signal. With the resonant coupling between Fano resonance and image dipole extinction, the oligonucleotide with a molecular weight of 5.5 kDa can be detected at a concentration of 100 fM. The resonant coupling dramatically pushes the sensitivity boundary, and we report the limit of detection (LOD) to be 3 orders of magnitude lower than that of the prism-based SPR. This study provides a promising and efficient method for detecting low concentrations of small molecules such as aptamers, miRNA, mRNA, and peptides.

Research Progress of Resonance Optical Fiber Sensors Modified by Low‐Dimensional Materials

“…In the field of the sensing region, the coupling effect between the LSPR characteristic of noble metal nanoparticles and the plasma wave on the surface of SPR sensor, the tips of these special structures can have the effect of local strong binding enhancing the field strength, which is attributed to the LSPR effect, which is one of the reasons for the sensitization effect of nanoparticles. [164][165][166][167] In addition, the adsorption of nanoparticles on the fiber surface increases the roughness of the sensing surface, and increases the surface area of the sensing region, thus improving the sensitivity of the sensor. [141] In addition to its own sensitization effect, porous nanoparticles can also fill their holes with sensitive materials, and the porous structure is conducive to the entry of the object to be measured into the particle and the full interaction with sensitive materials, thus facilitating the improvement of sensitivity.…”

Smart Nanostructured Materials for SARS-CoV-2 and Variants Prevention, Biosensing and Vaccination

“…By coupling periodic structures with plasmonic excitation, it is possible to offer new optical responses in biosensing [ 170 , 171 , 172 ]. Lattice plasmon resonance and Fano resonance are two representative examples, which provide highly sensitive platforms to detect biological species [ 173 , 174 , 175 , 176 , 177 , 178 ]. One reliable way to manufacture periodic plasmonic nanostructures is to deposit thin layer of metals on the surface of a template featuring periodic structures.…”

Differential Sensing with Replicated Plasmonic Gratings Interrogated in the Optical Switch Configuration

“…However, the COVID-19 pandemic highlighted and increased the need for portable and cost-effective biosensors to address challenges in large-scale testing and screening. Surface plasmon resonance (SPR) biosensors [ 1 , 2 ] and their integration into other systems [ 3 , 4 ] have been identified as a highly promising approach, offering the benefits of label-free, real-time, rapid detection to overcome the limitations of the laboratory-based techniques in current use, such as ELISA (enzyme-linked immunosorbent assay) [ 5 ] and RT-PCR (reverse transcription polymerase chain reaction) [ 6 ]. The most widespread SPR detection configuration is based on a prism coupler [ 7 ], and is rather cumbersome and expensive [ 8 ], attributes which do not align well with point-of-care (POC) settings.…”