Abstract
Several major lung pathologies are characterized by early modifications of the extracellular matrix (ECM) fibrillar collagen and elastin network. We report here the development of a nonlinear fiber-optic spectrometer, compatible with an endoscopic use, primarily intended for the recording of second-harmonic generation (SHG) signal of collagen and two-photon excited fluorescence (2PEF) of both collagen and elastin. Fiber dispersion is accurately compensated by the use of a specific grism-pair stretcher, allowing laser pulse temporal width around 70 fs and excitation wavelength tunability from 790 to 900 nm. This spectrometer was used to investigate the excitation wavelength dependence (from 800 to 870 nm) of SHG and 2PEF spectra originating from ex vivo human lung tissue samples. The results were compared with spectral responses of collagen gel and elastin powder reference samples and also with data obtained using standard nonlinear microspectroscopy. The excitation-wavelength-tunable nonlinear fiber-optic spectrometer presented in this study allows performing nonlinear spectroscopy of human lung tissue ECM through the elastin 2PEF and the collagen SHG signals. This work opens the way to tunable excitation nonlinear endomicroscopy based on both distal scanning of a single optical fiber and proximal scanning of a fiber-optic bundle.
Highlights
Nonlinear optical microscopy is a powerful method which is widely used for in vitro tissue imaging
A number of investigations on fresh mouse [10] and human [11,12,13,14] lung samples demonstrated that nonlinear microscopy, combining second-harmonic generation (SHG) and 2PEF, is effective in imaging the elastin and collagen network microstructure and can be used to assess the pathological changes occurring in extracellular matrix (ECM) organization
Further work is needed to investigate this behavior. All these results clearly indicate that the lung tissue 2PEF emission, from 750 to 870 nm excitation wavelengths, originates predominantly from ECM elastin fibers
Summary
Nonlinear optical microscopy is a powerful method which is widely used for in vitro tissue imaging It is of particular value for imaging extracellular matrix (ECM) architecture since the combination of second-harmonic generation (SHG) and two photon excited fluorescence (2PEF) allows the simultaneous visualization of collagen (SHG) and elastin (2PEF), the main ECM proteins [1,2,3,4]. A number of investigations on fresh mouse [10] and human [11,12,13,14] lung samples demonstrated that nonlinear microscopy, combining SHG and 2PEF, is effective in imaging the elastin and collagen network microstructure and can be used to assess the pathological changes occurring in ECM organization These studies showed the potential of this technique for early detection of lung diseases affecting the ECM. It would be of great clinical value to follow structural remodeling of the ECM in vivo during an endoscopic procedure
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
