Elastin is an essential and widespread structural protein in charge of the integrity on tissues and organs. In this study, we demonstrate that elastin is a major origin of the third-harmonic-generation (THG) contrast under Cr:forsterite laser excitation operating at 1230nm, with selective visualization inside many tissues such as lung tissues and arteries. In vivo imaging of the nude mouse elastic cartilage beneath the hypodermis by epi- THG microscopy keeps the high resolution and contrast in all three dimensions. Combined with second-harmonic-generation microscopy, THG microscopy exhibits the ability to show the extraordinary proliferation of elastic fibers for the ophthalmic disease of pterygium and the capability of distinguishable visualization from collagen.
The cornea functions as an optical lens and plays an important role in vision. For corneal diagnosis and treatment such as refractive surgery, a microscopic imaging system with a 3-D cellular resolution and retinal safety is strongly desired. Recently, confocal and multiphoton microscopies have been applied to corneal imaging with visible to near-infrared light sources. To increase retinal safety, an infrared light source is be needed. In this work, an infrared-based third and second harmonic generation microscopic study of mouse eyes is reported with approximately 700-mum penetrability and high cellular resolution. This study provides a critical reference for future development of infrared-based corneal imaging.
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