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. 2018 Jan 2;9(2):373-386.
doi: 10.1364/BOE.9.000373. eCollection 2018 Feb 1.

Extreme sensitive metasensor for targeted biomarkers identification using colloidal nanoparticles-integrated plasmonic unit cells

Arash Ahmadivand  1 , Burak Gerislioglu  1 , Asahi Tomitaka  2 , Pandiaraj Manickam  3   4 , Ajeet Kaushik  2 , Shekhar Bhansali  3 , Madhavan Nair  2 , Nezih Pala  1
Affiliations

Extreme sensitive metasensor for targeted biomarkers identification using colloidal nanoparticles-integrated plasmonic unit cells

Arash Ahmadivand et al. Biomed Opt Express. .

Abstract

Engineered terahertz (THz) plasmonic metamaterials have emerged as promising platforms for quick infection diagnosis, cost-effective and real-time pharmacology applications owing to their non-destructive and harmless interaction with biological tissues in both in vivo and in vitro assays. As a recent member of THz metamaterials family, toroidal metamaterials have been demonstrated to be supporting high-quality sharp resonance modes. Here we introduce a THz metasensor based on a plasmonic surface consisting of metamolecules that support ultra-narrow toroidal resonances excited by the incident radiation and demonstrate detection of an ultralow concertation targeted biomarker. The toroidal plasmonic metasurface was designed and optimized through extensive numerical studies and fabricated by standard microfabrication techniques. The surface then functionalized by immobilizing the antibody for virus-envelope proteins (ZIKV-EPs) for selective sensing. We sensed and quantified the ZIKV-EP in the assays by measuring the spectral shifts of the toroidal resonances while varying the concentration. In an improved protocol, we introduced gold nanoparticles (GNPs) decorated with the same antibodies onto the metamolecules and monitored the resonance shifts for the same concentrations. Our studies verified that the presence of GNPs enhances capturing of biomarker molecules in the surrounding medium of the metamaterial. By measuring the shift of the toroidal dipolar momentum (up to Δω~0.35 cm-1) for different concentrations of the biomarker proteins, we analyzed the sensitivity, repeatability, and limit of detection (LoD) of the proposed toroidal THz metasensor. The results show that up to 100-fold sensitivity enhancement can be obtained by utilizing plasmonic nanoparticles-integrated toroidal metamolecules in comparison to analogous devices. This approach allows for detection of low molecular-weight biomolecules (≈13 kDa) in diluted solutions using toroidal THz plasmonic unit cells.

Keywords: (040.2235) Far infrared or terahertz; (250.5403) Plasmonics; (280.1415) Biological sensing and sensors; (300.6495) Spectroscopy, terahertz.

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Conflict of interest statement

The authors declare that there are no conflicts of interest related to this article.

Figures

Fig. 1
Fig. 1
(a) Artistic rendering of the toroidal unit cell. (b) Geometrical parameters of the unit cell. (c) SEM image of the fabricated metasurface. (d) Schematics of the formation of head-to-tail arrangement correlating with the toroidal momentum between the proximal resonators with the direction of magnetic momenta. (e) A schematic representation of the BWO setup used to characterize the spectral response of the metasensor.
Fig. 2
Fig. 2
(a), (b), and (c) Normalized transmission amplitude for the toroidal metamaterials with three different gap distances g=7 μm, 5 μm, and 3 μm, respectively.(d) Local near-field map of the E-field enhancement at the gaps at the toroidal mode frequency. (e) Surface current plot for the current across the structure and formation of toroidal mode. (f) A cross-sectional yz-plane of the resonators, showing the head-to-tail magnetic moments forming the toroidal moment in a vectorial map.
Fig. 3
Fig. 3
(a) Surface current as a function of x-axis for three different gap spacing. (b) The toroidal scattering intensity as a function of frequency for three different gap spacing. (c) The Q factor of the toroidal lineshape and dephasing time (τ) as a function of three different gap spacing.
Fig. 4
Fig. 4
(a) Schematic flowchart of functionalized gold nanoparticle conjugation with the ZIKV-AB and ZIKV-EPs NS1 with the explanation for different parts. (b) Schematic representation of gold nanoparticles-integrated toroidal unit cells. (c) and (d) The SEM images of plasmonic metamolecule in the presence of GNPs with AB and ZIKV-EPs, respectively.
Fig. 5
Fig. 5
(a), (b) TEM images of functionalized GNPs binding with AB in two different scales. (c) The TEM image of ZIKV-EPs captured by AB-conjugated GNPs.
Fig. 6
Fig. 6
(a) The transmission amplitude spectra for the fabricated metasurfaces in both W/ and W/O GNPs regimes in the presence of ZIKV-AB and ZIKV-EPs with different concentrations. (b) The toroidal resonance shift as a function of ZIKV-EPs concentration W/ and W/O GNPs with the corresponding determination coefficient. (c) The magnified transmission spectra as a function of frequency, showing the maximum shift of the toroidal moment in the presence and absence of GNPs attached to the system.
Fig. 7
Fig. 7
(a) and (b) The toroidal resonance shift (Δω) and Q factor as a function to time in hours for the presence and absence of GNPs, respectively.
See this image and copyright information in PMC

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