Plasmonic photonic biosensor: in situ detection and quantification of SARS-CoV-2 particles

Highly scalable solid-core inhibited-coupling fiber-based plasmonic refractive index sensor

Advancements in plasmonic sensing require simultaneous detection capability that ensures large-scale detection with reduced losses. In this work, we propose a new solid-core fiber-based refractive index (RI) sensor with an ultra-broad detection range. The proposed fiber consists of a relatively simple single-ring cladding with six circular tubes in which the light is guided in the core based on the inhibited-coupling (IC) mechanism. The sensing performance is investigated using extensive finite-element modeling (FEM) through the combination of IC and surface plasmon resonance (SPR) sensing technology. Our results show a low loss of <3 dB/cm across the RI detection range from 1 to 1.60, peaking the wavelength sensitivity (WS) of 3000 nm/RIU and figure of merit (FOM) of 120 RIU-1. Our study also includes the investigation of the fabrication tolerance, fiber bending, and the use of alternative plasmonic materials, providing insights into the practical implementation capability of the proposed sensor. Our findings highlight the potential of the proposed sensor in emerging applications such as detecting air pollutants, biochemical substances, and DNA, paving the way towards bio-sensing within a lab-on-a-chip platform.

Rapid, sensitive and multiplexed detection of SARS-CoV-2 viral nucleic acids enabled by phase-based surface plasmon resonance of metallic gratings

A rapid, sensitive and easy-to-implement approach is proposed for the detection of pathogenic nucleic acids based on phase-based plasmonic spectroscopy of metallic gratings. The plasmonic sensors were fabricated using interference lithography and functionalized with single-stranded DNA probes to specific target SARS-CoV-2. The biosensor achieved the detection of 40 fM viral nucleic acids within 5 min; furthermore, a detection capability of 1 aM (0.6 copies/µL) was acquired when combining with the recombinase polymerase amplification. Additionally, the multiplexed sensing system was demonstrated to simultaneously detect three genomic sequences on a single sensor chip, thereby enhancing diagnostic accuracy and enabling high-throughput detection.

Hump-shaped seven-core fiber-based WaveFlex biosensor for rapid detection of glyphosate pesticides in real food samples

At present, pesticides are widely used in the cultivation of crops. Glyphosate is widely used in many pesticides. Glyphosate ingestion can cause a series of health problems. Therefore, this paper proposes to use localized surface plasmon resonance (LSPR) technology to develop a WaveFlex biosensor (plasma wave-based optical fiber sensor) to detect glyphosate concentration in pesticides. The evanescent field is improved by using the fusion of seven-core fiber and single-mode fiber and the tapering of the sensing area to improve the sensing performance. The gold nanoparticles (AuNPs) are used to excite the LSPR effect. Multi-walled carbon nanotubes (MWCNTs) and cerium oxide nanorods (CeO2-NRs) are used to increase the surface area and promote the adhesion of the enzyme. The sensitivity of the sensor is 137.7 pm/µM in the range of 0-60 µM glyphosate concentration, and the limit of detection (LoD) is 1.94 µM, which has good performance in compared to the existing biosensors. Subsequently, the sensor was tested for reusability, reproducibility, selectivity, stability, and excellent results were obtained. Finally, the sensor is tested on real samples, and the results show that it can be applied in practical applications. The test findings demonstrate that the sensor has a great deal of potential for use in glyphosate content detection in food samples.

Dual core photonic crystal fiber based plasmonic refractive index sensor with ultra-wide detection range

In this study, an ultra-wide range plasmonic refractive index sensor based on dual core photonic crystal fiber is suggested and analyzed numerically. The proposed design achieves fabrication feasibility by employing external sensing mechanism in which silver is deposited onto the flat outer surface of the fiber as plasmonic material. A thin layer of titanium oxide (TiO2) is considered on top of the silver layer for preventing its oxidation problem. The sensor attains identification of a vast array of analytes consisting a wide range of refractive indices of 1.10 - 1.45. It achieves a maximum spectral sensitivity of 24300 nm/RIU along with its corresponding resolution of 4.12 × 10-6 RIU. The maximum figure of merit of the sensor is 120 RIU-1. The sensor also supports amplitude interrogation approach and exhibits a maximum amplitude sensitivity of 172 RIU-1. The impact of the design parameters such as radius of air holes, polishing distance, thickness of silver and titanium oxide layers are investigated thoroughly. An ultra-wide detection range with high sensitivity, fabrication feasibility, and easy application make the sensor a potential candidate for detection of a wide array of bio-originated materials, chemicals, and other analytes.

A Novel SPR Immunosensor Based on Dual Signal Amplification Strategy for Detection of SARS-CoV-2 Nucleocapsid Protein

Since the global outbreak of coronavirus disease 2019 (COVID-19), it has spread rapidly around the world. The nucleocapsid (N) protein is one of the most abundant SARS-CoV-2 proteins. Therefore, a sensitive and effective detection method for SARS-CoV-2 N protein is the focus of research. Here, we developed a surface plasmon resonance (SPR) biosensor based on the dual signal-amplification strategy of Au@Ag@Au nanoparticles (NPs) and graphene oxide (GO). Additionally, a sandwich immunoassay was utilized to sensitively and efficiently detect SARS-CoV-2 N protein. On the one hand, Au@Ag@Au NPs have a high refractive index and the capability to electromagnetically couple with the plasma waves propagating on the surface of gold film, which are harnessed for amplifying the SPR response signal. On the other hand, GO, which has the large specific surface area and the abundant oxygen-containing functional groups, could provide unique light absorption bands that can enhance plasmonic coupling to further amplify the SPR response signal. The proposed biosensor could efficiently detect SARS-CoV-2 N protein for 15 min and the detection limit for SARS-CoV-2 N protein was 0.083 ng/mL, with a linear range of 0.1 ng/mL~1000 ng/mL. This novel method can meet the analytical requirements of artificial saliva simulated samples, and the developed biosensor had a good anti-interference capability.