MICRO-RAMAN SPECTROSCOPIC STUDY OF ORGAN-CULTURED CORNEAE

Raman spectroscopy of water was used to assess the metabolic state of fresh corneae and those which had been stored under long-term organ cu lture conditions. Both human and porcine tissue were employed. The dat a showed a semi-quantitative relationship between corneal hydration (d etermined using wet and dry weights of the tissue) and the integrated intensity of the water to collagen bands in the spectral region 2700-4 000 cm(-1). Variables included duration of storage, composition of cul ture medium and, for the human specimens, the age of the cornea. Raman assessment of hydration may provide a better measure of the functiona l state of the stored cornea that the density of live endothelial cell s, which is a commonly used criterion. The spectra showed that the hea lthy cornea of low water content contained more weakly hydrogen-bonded water than either bulk water or a swollen cornea. This is to be expec ted as groups on proteins and proteoglycans in the cornea form weak bo nds with water. These weakly bonded surface groups are diluted when wa ter is imbibed, hence resulting in the spectrum becoming more like tha t of bulk water in swollen tissue. Addition to the culture medium of d extran, which osmotically thins the cornea, converted its water spectr um back towards that of a healthy cornea.