SciQuest.org

Collagen is one the important load-bearing components in the body and the collagen structure has a distinct role in mechanical properties of the tissue. One of the challenges today is to visualize the collagen structure in live tissues or fresh tissues without fixing the tissue. It's clear that fixing methods are invasive and may alter the tissue structure. As an example, in tissue engineering experiments, visualization of changes in collagen three dimensional structure is essential for the understanding of collagen fibrils formation and remodeling.

Fluorescent CNA35 collagen probe developed in the laboratory of macromolecular and organic chemistry, Eindhoven University of Technology, The Netherlands, shows much specificity to collagen compared to other existing fluorescent techniques currently used for collagen visualization in live tissues and shows improved details compared to SHG ( second harmonic generation microscopy). However, in my opinion, the tissue should be relatively thin to let the prob perfuse all over the tissue.

The figure shows a mouse carotid artery, (Up) SHG signal of collagen (green), (down) fluorescence signal of collagen probe (green, CNA35-OG488) in a mouse carotid artery recorded at the same focal position obtained with two-photon laser scanning microscopy (15 μm deep)

reference:
High resolution imaging of collagen organisation and synthesis using a versatile collagen specific probe, Journal of Structural Biology
Volume 159, Issue 3, September 2007, Pages 392-399