Abstract
For the early diagnosis of several diseases, various biomarkers have been discovered and utilized through the measurement of concentrations in body fluids such as blood, urine, and saliva. The most representative analytical method for biomarker detection is an immunosensor, which exploits the specific antigen-antibody immunoreaction. Among diverse analytical methods, surface plasmon resonance (SPR)-based immunosensors are emerging as a potential detection platform due to high sensitivity, selectivity, and intuitive features. Particularly, SPR-based immunosensors could detect biomarkers without labeling of a specific detection probe, as typical immunosensors such as enzyme-linked immunosorbent assay (ELISA) use enzymes like horseradish peroxidase (HRP). In this review, SPR-based immunosensors utilizing noble metals such as Au and Ag as SPR-inducing factors for the measurement of different types of protein biomarkers, including viruses, microbes, and extracellular vesicles (EV), are briefly introduced.
Highlights
The optoelectronic phenomenon of surface plasmon resonance (SPR), which is widely utilized in optical biosensors, was established from studies involving excitation of surface plasmons on metallic surfaces, especially noble metals [1,2,3,4]
When metallic surfaces are exposed to light, a photon is trapped near the metallic surface and prompts the electrons to move as a single electrical entity, which is known as surface plasmon (SP)
When a surface plasmon is confined on nanomaterials, this unique physical property is highly localized around the nanoparticle, leading to a non-propagating localized surface plasmon with a specific frequency (LSPR, localized surface plasmon resonance) [7,8]
Summary
The optoelectronic phenomenon of surface plasmon resonance (SPR), which is widely utilized in optical biosensors, was established from studies involving excitation of surface plasmons on metallic surfaces, especially noble metals [1,2,3,4]. Due to the much shorter electromagnetic decay length on the nanoparticles compared to gold films, which allow confining the response to a smaller sensing volume, LSPR-based sensor is known to be more sensitive to small molecular binding and less sensitive to bulk effects [23] Considering these advantages, both PSPR- and LSPR-based analytical methods have been extensively utilized to investigate bio/chemical molecular interactions for diagnostic purposes. Recent approaches have been extensively applied to utilize new bio-receptors such as aptamers and imprinted polymers for replacement of antibodies; antibody-based assays are still considered the primary choice for developing PSPR- and LSPR-based biosensors, owing to their superior affinity, selectivity, and stability [24,25] To this end, a wide range of antibody immobilization methods has been developed to achieve optimal consistency while maintaining the activity of immobilized antibodies. We hope that this review will provide brief and concise information on the development of SPR- and LSPR-based biosensors and emphasize research from various disciplines for further development and improvement of SPR- and LSPR-based analytical methods for more significant biomedical applications
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