Refractometric biosensing based on optical phase flips in sparse and short-range-ordered nanoplasmonic layers

Abstract

Noble metal nanoparticles support localized surface plasmon resonances (LSPRs) that are extremely sensitive to the local dielectric properties of the environment within distances up to 10-100 nm from the metal surface. The significant overlap between the sensing volume of the nanoparticles and the size of biological macromolecules has made LSPR biosensing a key field for the application of plasmonics. Recent advancements in evaluating plasmonic refractometric sensors have suggested that the phase detection of light can surpass the sensitivity of standard intensity-based detection techniques. Here, we experimentally confirm that the phase of light can be used to precisely track local refractive index changes induced by biomolecular reactions, even for dilute and layers of short-range-ordered plasmonic nanoparticles. In particular, we demonstrate that the sensitivity can be enhanced by tuning in to a zero reflection condition, in which an abrupt phase flip of the reflected light is achieved. Using a cost-effective interference fringe tracking technique, we demonstrate that phase measurements yield an approximately one order of magnitude larger relative shift compared with traditional LSPR measurements for the model system of NeutrAvidin binding to biotinylated nanodisks.

Extreme sensitivity biosensing platform based on hyperbolic metamaterials

“…However, SPP sensors benefit from a high sensitivity to refractive index changes of ≈2 × 10 6 response units per RIU for a defined planar gold film area and surface coverage by a particular analyte 22 . On the other hand, LSP-based sensors perform well in some instances, particularly for smaller molecule detection, by precisely tracking the local refractive index changes due to biomolecular reactions by using the concept of optical phase flips 11 . Recent progress in microfabrication and nanofabrication has encouraged the development of novel labelfree plasmonic biosensors, particularly metamaterials, which can overcome the limitations of conventional plasmonic sensors [12][13][14][23][24][25][26] .…”

“…We report the ability of the metamaterial platform to detect ultralow-molecular-weight (244 Da) biomolecules at picomolar concentrations using a standard a nity model streptavidin-biotin. P lasmonic biosensors allow the rapid detection of biomolecular interactions in real time, which is particularly valuable for the diagnosis of diseases and routine point-of-care (POC) clinical evaluations [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . The basic principle of the plasmonic sensing mechanism is the excitation of charge density oscillations (surface plasmons) propagating along the metal/dielectric interface when the wavevector of incident light satisfies the resonant condition 17 .…”

Hyperbolic metamaterials-based plasmonic biosensor for fluid biopsy with single molecule sensitivity

“…SPP sensors are usually built in a Kretschmann configuration that matches momentum between the surface plasmon and a laser beam, whereas LSP sensors exhibit a tunable resonant frequency that does not require momentum matching [7,8]. LSP sensors geometrically confine electromagnetic energy absorbed from large optical crosssections to significantly enhance local fields within 5-15 nm of the nanoparticle surface [9][10][11]. Although SP biosensors have proven to be successful and are commercialized, they still suffer from several issues: (i) for SPPs, using momentum coupling via the Kretschmann configuration requires bulky optical elements, a prism, which makes it not suitable for point of care (POC) applications.…”

Are plasmonic optical biosensors ready for use in point-of-need applications?

“…This confinement enhances the electric field at nanoscale around the metal nanoparticles, and such LSPR is sensitive to molecular binding especially for some small biological molecules. 121 3.5.2. Absorption/transmission.…”