Abstract
Abstract Lung cancer is the most frequently life-threatening disease and the prominent cause of cancer-related mortality among human beings worldwide, where poor early diagnosis and expensive detection costs are considered as significant reasons. Here, we try to tackle this issue by proposing a novel label-free and low-cost strategy for rapid detection and distinction of lung cancer cells relying on plasmonic toroidal metasurfaces at terahertz frequencies. Three disjoint regions are displayed in identifiable intensity-frequency diagram, which could directly help doctors determine the type of lung cancer cells for clinical treatment. The metasurface is generated by two mirrored gold split ring resonators with subwavelength sizes. When placing analytes on the metasurface, apparent shifts of both the resonance frequency and the resonance depth can be observed in the terahertz transmission spectra. The theoretical sensitivity of the biosensor over the reflective index reaches as high as 485.3 GHz/RIU. Moreover, the proposed metasurface shows high angular stability for oblique incident angle from 0 to 30°, where the maximum resonance frequency shift is less than 0.66% and the maximum transmittance variation keeps below 1.33%. To experimentally verify the sensing strategy, three types of non-small cell lung cancer cells (Calu-1, A427, and 95D) are cultured with different concentrations and their terahertz transmission spectra are measured with the proposed metasurface biosensor. The two-dimensional fingerprint diagram considering both the frequency and transmittance variations of the toroidal resonance dip is obtained, where the curves for different cells are completely separated with each other. This implies that we can directly distinguish the type of the analyte cells and its concentration by only single spectral measurement. We envisage that the proposed strategy has potential for clinical diagnosis and significantly expands the capabilities of plasmonic metamaterials in biological detection.
Highlights
Lung cancer is the second most widespread cancer that accounts for the highest number of cancer-related deaths worldwide [1, 2]
The robust angular stability of the toroidal metasurface biosensor is emphasized with a maximum frequency shift less than 0.66% related to center frequency and a maximum transmittance shift less than 1.33%, which would be helpful to reduce experimental errors and make potential progress for practical clinical applications
To experimentally verify the excellent sensing performance, three types of lung cancer cells are cultured on the surface of metasurface biosensor with different cell concentrations
Summary
Lung cancer is the second most widespread cancer that accounts for the highest number of cancer-related deaths worldwide [1, 2]. Light microscopy could be used to differentiate most of the histologic subtypes, while immunohistochemistry and gene sequencing compensate for it, which are performed more common on prognosis predictions and targeted medicine selections [7, 8] Those techniques are efficient, they are associated with many limitations such as time consuming, high demand for clinical experience, and restrictive experimental conditions. Bright and dark modes are simultaneously excited in meta-atoms with asymmetric structures such as spilt ring resonators (SRRs) Another category of metasurfaces, namely plasmonic toroidal metasurfaces [26,27,28,29,30], have excited a lot of interest owing to the feature of weak free-space coupling and unique light localization, which are crucial for achieving high quality factor (Q) response and enhanced light–matter interactions for sensing. Such a robust feature will greatly reduce the errors caused by experimental manipulation and expand the possibility for compact sensors
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