Monolayers of Silver Nanoparticles Decrease Photobleaching: Application to Muscle Myofibrils

Abstract

Studying single molecules in a cell has the essential advantage that kinetic information is not averaged out. However, since fluorescence is faint, such studies require that the sample be illuminated with the intense light beam. This causes photodamage of labeled proteins and rapid photobleaching of the fluorophores. Here, we show that a substantial reduction of these types of photodamage can be achieved by imaging samples on coverslips coated with monolayers of silver nanoparticles. The mechanism responsible for this effect is the interaction of localized surface plasmon polaritons excited in the metallic nanoparticles with the transition dipoles of fluorophores of a sample. This leads to a significant enhancement of fluorescence and a decrease of fluorescence lifetime of a fluorophore. Enhancement of fluorescence leads to the reduction of photodamage, because the sample can be illuminated with a dim light, and decrease of fluorescence lifetime leads to reduction of photobleaching because the fluorophore spends less time in the excited state, where it is susceptible to oxygen attack. Fluorescence enhancement and reduction of photobleaching on rough metallic surfaces are usually accompanied by a loss of optical resolution due to refraction of light by particles. In the case of monolayers of silver nanoparticles, however, the surface is smooth and glossy. The fluorescence enhancement and the reduction of photobleaching are achieved without sacrificing the optical resolution of a microscope. Skeletal muscle myofibrils were used as an example, because they contain submicron structures conveniently used to define optical resolution. Small nanoparticles (diameter approximately 60 nm) did not cause loss of optical resolution, and they enhanced fluorescence approximately 500-fold and caused the appearance of a major picosecond component of lifetime decay. As a result, the sample photobleached approximately 20-fold more slowly than the sample on glass coverslips.

Controlling the Synthesis and Assembly of Silver Nanostructures for Plasmonic Applications

“…250,341,344,456–458 Figure 21A shows a comparison of the lifetime images of two fluorescently stained cells grown on either a glass cover slip or a Ag nanoparticle island film (i.e., Ag nanoparticles deposited on a glass cover slip). 459 The fluorescence from the stained membranes of the cells on the Ag film had a lifetime that was 2.0 ns shorter and had a 3× larger photostability due to SEF.…”

Lanthanides in Solar Energy Conversion

“…The physics behind the phenomenon is rather complex and depending on the size of the metallic colloidal particles either luminescence quenching or enhancement can be generated (Lakowicz, 2005). Since not only metalenhanced luminescence is achieved but also reduction in photobleaching (Muthu et al, 2008), the technique is starting to find applications in biosciences (Bünzli, 2013), photocatalysis (Thomann et al, 2011), and photovoltaics (Giannini et al, 2011). The incident electric field from the electromagnetic wave is modified by interacting with the metal surface, resulting in strong coupling between the surface plasmons of the metal particles and the transition dipoles of the chromophore.…”

Preparation of Plasmonic Platforms of Silver Wires on Gold Mirrors and Their Application to Surface Enhanced Fluorescence

“… 6 − 9 Optimal conditions to improve fluorescence sensitivities for practical applications of single molecule detection have been of great interest. 10 , 11 …”