Biomolecular Sensing at the Interface between Chiral Metasurfaces and Hyperbolic Metamaterials

Abstract

In recent times, biomolecular sensing to recognize genetic fragments and proteins is spurring unprecedented interest as a diagnostic protocol for cancer and infectious diseases. Significant efforts have been made to design nanomaterials able to control the light–matter interaction at the single nanometer scale, where genes and proteins bind specifically to receptors. Here, we numerically show how the interface between a chiral metasurface and hyperbolic metamaterials can enable both high sensitivity and specificity for low-molecular-weight nucleic acids and proteins. As we have recently reported, hyperbolic dispersion metamaterials allow molecular biorecognition with extreme sensitivity because of coupled and highly confined plasmon polaritons. Specificity is almost exclusively achieved by receptor–ligand interaction at the in-plane sensing surface. Interestingly, an adapted out-of-plane chiral metasurface enables three key functionalities of the hyperbolic metamaterial sensor. Computational effort reveals that helicoidal metasurfaces can act as (i) efficient diffractive elements to excite surface and bulk plasmon polaritons; (ii) out-of-plane sensing branches to reduce the diffusion limit and increase the sensing surface; and (iii) biorecognition assay also via circular dichroism and chiral selectivity.

Hyperbolic dispersion metasurfaces for molecular biosensing

“…The interface between a chiral metasurface and hyperbolic metamaterials can enable both high sensitivity and specificity for low-molecular-weight nucleic acids and proteins [111][112][113][114][115]. Interestingly, an adapted out-of-plane chiral metasurface enables three key functionalities of the HMM sensor: (i) an efficient diffractive element to excite surface and bulk plasmon polaritons [76,109]; (ii) an increase in the total sensing surface enabled via out-of-plane binding, improving diffusion-limited detection of small analyte concentrations; and (iii) additional biorecognition assays via circular dichroism (CD) and chiral selectivity that can be optimally tailored to amplify the chiral-chiral interactions between the metamaterial inclusions and the molecules, enabling high-sensitivity handedness detection of enantiomers [116][117][118][119][120]. A sketch of a chiral metasurface hypergrating (CMH), consisting of a periodic array of right-handed Au helices on a type II HMM composed by indium tin oxide (ITO -20 nm) and silver (Ag -20 nm) is shown in Figure 9a.…”

“…This miniaturized multimode sensor exhibited extreme bulk RI sensitivity with a record figure of merit (FOM) and detected biotin concentrations as low as 10 pM. Since then different hyperbolic dispersion metamaterials have been proposed for sensitivity enhancement purposes [72][73][74][75][76][77][78][79][80][81][82].…”

Metamaterials-Enabled Sensing for Human-Machine Interfacing

“…To avoid the high loss at the visible band due to the high imaginary part of the permittivity of some metamaterials, the epsilon-near-zero (ENZ) metamaterials, whose real part of permittivity may approach zero, show much intrinsic superiority over conventional materials. ENZ metamaterials emerge in recent years with a lot of functionalities and applications, such as invisible cloaking, nano-optical circuits, nonlinear optics and so on, but the practical fabrication remains challenging [78][79][80][81][82][83]. Fusco et al engineered a kind of nanostructured sodium tungsten bronze (Na x WO 3 ) ENZ metamaterials for achieving optical sensing [73].…”

Hyperbolic dispersion metamaterials and metasurfaces

“…The interface between a chiral metasurface and hyperbolic metamaterials can enable both high sensitivity and specificity for low molecular weight nucleic acids and proteins [36][37][38][39][40]. Interestingly, an adapted out-of-plane chiral metasurface enables three key functionalities of the HMM sensor: (i) an efficient diffractive element to excite surface and bulk plasmon polaritons; [32,41] (ii) an increase in the total sensing surface enabled via out-of-plane binding, improving diffusion-limited detection of small analyte concentrations; (iii) additional biorecognition assays via circular dichroism and chiral selectivity that can be optimally tailored to amplify the chiral-chiral interactions between the metamaterial inclusions and the molecules, enabling high-sensitivity handedness detection of enantiomers [42][43][44][45][46].…”