Double-label immunofluorescence with the laser scanning confocal microscope using cyanine dyes

Area of Science:

• Immunofluorescence microscopy
• Cell biology
• Neuroscience

Background:

• Confocal microscopy enables simultaneous detection of multiple antigens.
• Traditional double-labeling uses fluorescein isothiocyanate (FITC) and Texas Red, excited by blue and yellow light, respectively.
• Autofluorescence in tissues, particularly at low wavelengths, can obscure signals when using FITC.

Purpose of the Study:

• To develop a superior immunofluorescence method for double-labeling studies in tissues with inherent autofluorescence.
• To overcome limitations of FITC-based detection in amphibian cardiac ganglion studies.

Main Methods:

• Utilized a krypton-argon ion laser scanning confocal microscope.
• Employed cyanine 3.18 (Cy3) and cyanine 5.18 (Cy5) conjugated secondary antibodies.
• Excited Cy3 and Cy5 with yellow (568 nm) and red (647 nm) laser lines, respectively, avoiding the problematic blue (488 nm) line.

Main Results:

• Cy3 and Cy5 antibodies emit in the orange/red and far-red spectrum, respectively.
• This method effectively avoids autofluorescence issues present with 488 nm excitation.
• Achieved image quality comparable to or better than FITC/Texas Red, even in autofluorescent tissues.

Conclusions:

• Cyanine dye-based immunofluorescence provides a robust solution for double-labeling in autofluorescent tissues.
• This technique enhances the analysis of cellular structures, such as receptor clusters and synaptic boutons, in challenging biological samples.
• The method offers improved visualization without the interference of low-wavelength autofluorescence.