All-optical correlative micro-spectroscopies in the investigation of stromal collagen morpho-mechanics

Tissue morpho-mechanics is gaining increasing in various fields, because it targets the relationship between morphological features and mechanical properties in biological tissues, which plays an important role in various fields including biology, medicine, pathology, tissue engineering, and regenerative medicine. The intimate connection between morphological, biochemical and mechanical properties in biological tissues requires a multimodal correlative approach for their exhaustive investigation. In this study, we used Second-Harmonic Generation in combination with Brillouin and Raman micro-spectroscopy in order to correlate collagen morphology at the ultrastructural level with its biomechanical and biochemical features. In particular, by imaging human corneal tissue samples with our multimodal approach, we demonstrated that the peculiar mechanical properties of corneal lamellae in the anterior portion of the corneal stroma are due to a different supramolecular organization, rather than to a different biochemical composition. This result opens new insights in the study and interpretation of corneal biomechanics thanks to the possibility of non-invasively correlating lamellar morphology with visco-elastic properties. The proposed method opens the way to the non-invasive assessment of corneal morpho-mechanics and holds the potential to be used for both diagnostic and follow-up purposes in pathologies that affect corneal biomechanics.