Thickness-Sensing Sandwiched Plasmonic Biosensors Enable Label-Free Naked-Eye Antibody Quantification

Abstract

Clinical serology assays for detecting the antibodies of the virus are time-consuming, are less sensitive/selective, or rely on sophisticated detection instruments. Here, we develop a sandwiched plasmonic biosensor (SPB) for supersensitive thickness-sensing via utilizing the distance-dependent electromagnetic coupling in sandwiched plasmonic nanostructures. SPBs quantitatively amplify the thickness changes on the nanoscale range (sensitivity: ∼2% nm–1) into macroscopically visible signals, thereby enabling the rapid, label-free, and naked-eye detection of targeted biomolecular species (via the thickness change caused by immunobinding events). As a proof of concept, this assay affords a broad dynamic range (7 orders of magnitude) and a low LOD (∼0.3 pM), allowing for the extremely accurate SARS-CoV-2 antibody quantification (sensitivity/specificity: 100%/∼99%, with a portable optical fiber device). This strategy is suitable for high-throughput multiplexed detection and smartphone-based sensing at the point-of-care, which can be expanded for various sensing applications beyond the fields of viral infections and vaccination.

Plasmonic and metamaterial biosensors: a game-changer for virus detection

“…208 This assay provided a broad dynamic range (7 orders of magnitude) and a low LOD of 0.3 pM, leading to accurate SARS-CoV-2 antibody quantification (sensitivity/specificity of 100%/99%, with a portable optical fiber device). 208 Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was successfully performed in a reaction vessel containing PCR chemistry, fluorescent probes, and plasmonic nanoparticles using plasmonic thermocycling, in which rapid heating of the solution was achieved via infrared excitation of gold nanorods. 209 The authors achieved SARS-CoV-2 RNA detection in human saliva and nasal specimens with 100% sensitivity and 100% specificity.…”

“…According to the authors, SERS signals increased by 10 times in the detection limit from 1 fM to 100 aM 159 . A plasmonic biosensor for thickness-sensing detection via utilizing the distance-dependent electromagnetic coupling in sandwiched Au nanoparticles and Au film structures was demonstrated for naked-eye detection of antibodies against SARS-CoV-2 208 . This assay provided a broad dynamic range (7 orders of magnitude) and a low LOD of 0.3 pM, leading to accurate SARS-CoV-2 antibody quantification (sensitivity/specificity of 100%/99%, with a portable optical fiber device) 208 .…”

“…A plasmonic biosensor for thickness-sensing detection via utilizing the distance-dependent electromagnetic coupling in sandwiched Au nanoparticles and Au film structures was demonstrated for naked-eye detection of antibodies against SARS-CoV-2 208 . This assay provided a broad dynamic range (7 orders of magnitude) and a low LOD of 0.3 pM, leading to accurate SARS-CoV-2 antibody quantification (sensitivity/specificity of 100%/99%, with a portable optical fiber device) 208 . Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was successfully performed in a reaction vessel containing PCR chemistry, fluorescent probes, and plasmonic nanoparticles using plasmonic thermocycling, in which rapid heating of the solution was achieved via infrared excitation of gold nanorods 209 .…”

Recent Advances in Nanomaterials‐Based FETs for SARS‐CoV‐2 (COVID‐19 Virus) Diagnosis

“…The detailed results of the optical analysis are displayed as a histogram. b-f) Adapted with permission [150]. Copyright 2022, American Chemical Society.…”

NIR-II Imaging and Sandwiched Plasmonic Biosensor for Ultrasensitive Intraoperative Definition of Tumor-Invaded Lymph Nodes

“…It is also difficult to distinguish tumor micrometastasis from other normal structures, and false-negative detection is a hidden danger in postoperative recurrence . For this purpose, we developed an SPC immunoassay biosensor, which provides fast/low-cost manufacturing steps and a visible diagnostic output signal, enabling the rapid and label-free detection of tumors with the microscope or naked-eye (smartphone) readouts in intraoperative tumor detection and tumor-invaded LNs detection. SPC could function as a powerful addition to the NIR-II imaging-navigation system.…”