Investigation on fibrous collagen modifications during corneal laser welding by second harmonic generation microscopy

Year: 2009

Authors: Matteini P., Ratto F., Rossi F., Cicchi R., Stringari C., Kapsokalyvas D., Pavone FS., Pini R.

Autors Affiliation: CNR, Ist Fis Applicata Nello Carrara, Sesto Fiorentino, Italy;
European Laboratory for Non-linear Spectroscopy,
University of Florence, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy;

Abstract: The structural modifications in the collagen lattice of corneal stroma induced by near-infrared laser welding were investigated with second-harmonic generation (SHG) imaging. The corneal laser welding procedure is performed by staining the wound edges with a saturated water solution of Indocyanine Green (ICG) followed by irradiation with a 810 nm diode laser operated in continuous (CWLW: continuous wave laser welding) or pulsed (PLW: pulsed laser welding) mode. Both these procedures can provide closure of corneal wounds by inducing different structural modifications in the extracellular matrix. SHG imaging of native corneal stroma revealed collagen bundles composed of many regularly aligned collagen fibrils. After CWLW the regular lamellar arrangement was lost; collagen bundles appeared densely packed with an increasing disordered arrangement toward the welded cut. The weld was characterized by a loss of details; nevertheless, the observation of the second harmonic signal at this site indicated the lack of collagen denaturation. By contrast, PLW mode produced welding spots at the interface between donor and recipient corneal layers, which were characterized by a severe loss of the SHG signal, suggesting the occurrence of a complete collagen denaturation. SHG imaging appeared to be a powerful tool for visualizing the supramolecular morphological modifications in the collagen matrix after laser welding.

Conference title: Photonics West – BIOS 2009
Place: San Francisco, US

KeyWords: Collagen denaturations; Collagen fibrils; Collagen matrices; Collagen modifications; Cornea; Corneal stromata; Diode lasers; Extra cellular matrices; Indocyanine Green; Laser-welding; Morphological modifications; Near-infrared lasers; Pulsed laser welding; Saturated waters; Second harmonic generation microscopies; Second harmonic signals; Second-harmonic generation microscopy; Shg signals; Structural modifications, Chemical modification; Collagen; Continuous wave lasers; Harmonic analysis; Harmonic generation; Infrared devices; Laser welding machines; Optical frequency conversion; Pulsed laser applications, Laser beam welding
DOI: 10.1117/12.808739

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