Surface plasmon–coupled emission imaging for biological applications

Abstract

Fluorescence imaging technology has been extensively applied in chemical and biological research profiting from its high sensitivity and specificity. Much attention has been devoted to breaking the light diffraction-limited spatial resolution. However, it remains a great challenge to improve the axial resolution in a way that is accessible in general laboratories. Surface plasmon-coupled emission (SPCE), generated by the interactions between surface plasmons and excited fluorophores in close vicinity of the thin metal film, offers an opportunity for optical imaging with potential application in analysis of molecular and biological systems. Benefiting from the highly directional and distance-dependent properties, SPCE imaging (SPCEi) has displayed excellent performance in bioimaging with improved sensitivity and axial confinement. Herein, we give a brief overview of the development of SPCEi. We describe the unique optical characteristics and constructions of SPCEi systems and highlight recent advances in the use of SPCEi for biological applications. We hope this review provides readers with both the insights and future prospects of SPCEi as a new promising imaging platform for potentially widespread applications in biological research and medical diagnostics.

Diattenuation and retardance signature of plasmonic gold nanorods in turbid media revealed by Mueller matrix polarimetry

“…For example, light incident onto a medium containing metallic nanoparticles causes excitation of localized surface plasmons, affecting the intensity and the spectral content of the reflected or transmitted light and thereby enhancing optical contrast 5 . Gold nanoparticles (GNPs) exhibit strong localized SPR effect and have thus been actively explored in biology and medicine 6 – 8 . Their strong confinement of EM waves and biocompatibility has spurred their use as multifunctional probes for molecular rulers 9 , single molecule detection 10 , photoactive drug delivery 11 , photodynamic therapy 12 , photothermal treatments 13 , stem cells targeting 14 , tumour and stromal microenvironment imaging 15 , and optical contrast enhancement 16 .…”

“…In this context, plasmonic gold nanospheres have not proven particularly useful because their plasmon resonance effects occur at shorter wavelengths, which owing to basic tissue optics limits their biomedical use 17 . However, plasmonic gold nanorods (GNRs) have been found to be more useful due to their geometry and aspect ratio dependent tunable plasmon mode which falls within the visible and near infrared spectral regime suitable for biomedical imaging 6 – 8 . Several studies have therefore focused on GNR delivery mechanism, their interaction with biological media, and their photoactivity 12 – 17 .…”

Titanium nitride as an alternative and reusable plasmonic substrate for fluorescence coupling

“…The advantages of SPCE have led to numerous applications in sensing of chemical and biochemical analytes at low concentrations, detection of DNA base mutations, immunoassays and imaging. 17–22 To improve the scope of SPCE and benefit from the surface plasmon field enhancement, a number of studies are being carried out to engineer the spacer layer between the metal and the fluorophore with the help of different materials like polymers, silicon, protein/DNA, carbon nanotubes and graphene. 1,22–24 However, the expansion of SPCE for practical applications is still hindered by the metallic component, which is typically limited to the conventional plasmonic materials, silver and gold.…”

Plasmon-Coupled Directional Emission from Soluplus-Mediated AgAu Nanoparticles for Attomolar Sensing Using a Smartphone

“…3−5 Dissimilar metallic or plasmonic nanofilms have been explored to study this phenomenon, along with different thicknesses of the dielectric layer to comprehend the waveguide and plasmon modes. 3,6 SPCE has endowed researchers with opportunities for exploring different optical phenomena, 7 chemical processes, 8 and biophysical sensing applications. 9−11 While plasmonic nanothin films support SPPs propagating over the continuous film, the plasmonic nanoparticles (NPs) support localized surface plasmon resonance (LSPR) sustaining intense electromagnetic (EM)-field localization in the nearfield.…”