Plasmon resonance and the imaging of metal-impregnated neurons with the laser scanning confocal microscope

Abstract

The staining of neurons with silver began in the 1800s, but until now the great resolving power of the laser scanning confocal microscope has not been utilized to capture the in-focus and three-dimensional cytoarchitecture of metal-impregnated cells. Here, we demonstrate how spectral confocal microscopy, typically reserved for fluorescent imaging, can be used to visualize metal-labeled tissues. This imaging does not involve the reflectance of metal particles, but rather the excitation of silver (or gold) nanoparticles and their putative surface plasmon resonance. To induce such resonance, silver or gold particles were excited with visible-wavelength laser lines (561 or 640 nm), and the maximal emission signal was collected at a shorter wavelength (i.e., higher energy state). Because the surface plasmon resonances of noble metal nanoparticles offer a superior optical signal and do not photobleach, our novel protocol holds enormous promise of a rebirth and further development of silver- and gold-based cell labeling protocols.DOI: http://dx.doi.org/10.7554/eLife.09388.001

Fluorescent Silver-AIE Visualization of Neurons and Fibres in the Cleared Brain

“…Silver/gold-impregnated tissues can be imaged by laser scanning confocal microscopy through surface plasmon resonance with special optical filter sets to capture the shorter emission wavelengths in reference to the excitation wavelengths. 20 It can also be used in 3D electron microscopy with automated tracing algorithm to visualize ultrastructural details of Golgi-stained neurons. 21,22 In the present work, AIE mechanism of TPE-4TA enhances the sensitivity of silver development and overcomes the uncertainty of Ag + reduction in silver staining.…”