Comparison of spectroscopic and biochemical determination of collagen crosslinks in cartilage

Type II collagen is the main protein of the articular cartilage matrix. Covalent inter-molecular crosslinking of collagen is the critical post-translational modification contributing to the ultimate mechanical properties of the tissue, and thus can be an important component of tissue quality in aging and disease. An HPLC biochemical assay, which is destructive, is the standard method for determination of crosslinks, This study assessed whether Fourier transform infrared (FT-IR) imaging spectroscopy, a technique based on molecular vibrations, could be used to assess crosslinks in bovine cartilage at high spatial resolution. HPLC determination of the ratio of mature to immature crosslinks (collagen maturity) in bovine tissue of different ages showed increases during aging, as expected. This was correlated to the FT-IRIS derived 1660/1690cm^-1 peak height ratio, a parameter previously shown to correlate to type I collagen crosslink maturity. Thus, is it possible that the same parameter could be used for crosslink assessment in type II collagen-based tissues as well.