Mechanobiology of soft tissues: FT-Raman spectroscopic studies

FT-Raman spectroscopy was used to investigate microstructural changes in the secondary protein structure of soft tissues subjected to increasing levels of macroscopic strain. Main protein bands at 938 cm-1 assigned as v(Cα–C), 1668 cm-1 — amide I and 1268 cm-1 — amide III are sensitive to applied strain and undergo wavenumber shifting. Other main vibrational modes at 1004 cm-1 assigned to the phenyl ring breathing mode and 2940 cm-1 (n(CH3,CH2)) remain unaltered. Spectroscopic results were compared with the mechanical relations obtained from the standard protocol of uniaxial tensile tests carried out in a testing machine. A clear correlation between Raman band shifting and the level of mechanical stress was established. Initially the load is transferred through elastin and then gradually also by collagen. It was proved that transferring loads by soft tissues involves changes in structural protein conformation. This process was described in detail for a tendon. It was also confirmed that mechanical properties of soft tissues depend on collagen and elastin fiers orientation.