Assays utilizing fluorophores are common throughout life science research and diagnostics, although detection limits are generally limited by weak emission intensity, thus requiring many labeled target molecules to combine their output to achieve higher signal‐to‐noise. We describe how the synergistic coupling of plasmonic and photonic modes can significantly boost the emission from fluorophores. By optimally matching the resonant modes of a plasmonic fluor (PF) nanoparticle and a photonic crystal (PC) with the absorption and emission spectrum of the fluorescent dye, a 52‐fold improvement in signal intensity is observed, enabling individual PFs to be observed and digitally counted, where one PF tag represents one detected target molecule. The amplification can be attributed to the strong near‐field enhancement due to the cavity‐induced activation of the PF, PC band structure‐mediated improvement in collection efficiency, and increased rate of spontaneous emission. The applicability of the method by dose‐response characterization of a sandwich immunoassay for human interleukin‐6, a biomarker used to assist diagnosis of cancer, inflammation, sepsis, and autoimmune disease is demonstrated. A limit of detection of 10 fg mL−1and 100 fg mL−1in buffer and human plasma respectively, is achieved, representing a capability nearly three orders of magnitude lower than standard immunoassays.
- Award ID(s):
- 1900277
- NSF-PAR ID:
- 10532052
- Publisher / Repository:
- International Conference on Surface Plasmon Photonics (SPP10)
- Date Published:
- Format(s):
- Medium: X
- Location:
- Houston, TX
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
The requirements of augmented signal contrast provided by nanoparticle tags in biosensor microscopy-based point-of-care technologies for cancer and infectious disease diagnostics can be addressed through metallo-dielectric nanoarchitectures that enhance optical scattering and absorption to provide digital resolution detection of single tags with simple instrumentation. Photonic Resonator Interferometric Scattering Microscopy (PRISM) enables label-free visualization of nanometer-scale analytes such as extracellular vesicles and virions, and its applicability can be extended to biomolecular analyte counting through nanoparticle tags. Here, we present template-free, linker-less cryosoret nano-assemblies fabricated via adiabatic cooling (−196 °C) as plasmonic nano-antennas that provide high scattering contrast in PRISM. Plasmonic Ag and Au nanomaterials and their cryosorets are evaluated through imaging experiments and simulations based on the finite element method to understand the photo-plasmonic coupling effect at the surface of a photonic crystal (PC) interface. The Ag and Au cryosorets provide at most 8.29-fold and 6.77-fold higher signal contrast compared to their singlet counterpart. Through the simulations, the averaged field magnitude enhancements of 2.77-fold and 3.68-fold are observed for Ag and Au cryosorets when interfacing with PCs compared to bare glass substrates. The hybrid coupling between the localized Mie and delocalized Bragg plasmons of cryosorets and the underlying PC's guided mode resonance provides insights for developing nano-assembly-based nano-tags for biosensing applications.
-
Abstract While nanoscale quantum emitters are effective tags for measuring biomolecular interactions, their utilities for applications that demand single-unit observations are limited by the requirements for large numerical aperture (NA) objectives, fluorescence intermittency, and poor photon collection efficiency resulted from omnidirectional emission. Here, we report a nearly 3000-fold signal enhancement achieved through multiplicative effects of enhanced excitation, highly directional extraction, quantum efficiency improvement, and blinking suppression through a photonic crystal (PC) surface. The approach achieves single quantum dot (QD) sensitivity with high signal-to-noise ratio, even when using a low-NA lens and an inexpensive optical setup. The blinking suppression capability of the PC improves the QDs on-time from 15% to 85% ameliorating signal intermittency. We developed an assay for cancer-associated miRNA biomarkers with single-molecule resolution, single-base mutation selectivity, and 10-attomolar detection limit. Additionally, we observed differential surface motion trajectories of QDs when their surface attachment stringency is altered by changing a single base in a cancer-specific miRNA sequence.more » « less
-
more » « less
Diagnostic assays utilizing fluorescent reporters in the context of low abundance biomarkers for cancer and infectious disease can reach lower limits of detection through efficient collection of emitted photons into an optical sensor. In this work, we present the rational design, fabrication, and application of one-dimensional photonic crystal (PC) grating interfaces to accomplish a cost-effective prism-free, metal-free, and objective-free platform for augmentation of fluorescence emission collection efficiency. Guided mode resonance (GMR) of the PC is engineered to match the laser excitation (532 nm) and emission maximum (580 nm) of the radiating dipoles to arrive at optimized conditions. The photo-plasmonic hybrid nano-engineering using silver nanoparticles presented >110-fold steering fluorescence enhancement enabling placement of the sample between the excitation source and detector that are in a straight line. From the experimental and simulation inferences, we propose a radiating GMR model by scrutinizing the polarized emission properties of the hybrid substrate, in accordance with the radiating plasmon model. The augmented fluorescence intensity realized here with a simple detection instrument provides sub-nanomolar sensitivity to provide a path toward point-of-care scenarios.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
