Characterisation of skin states by non-crystalline diffraction

Abstract

Small angle X-ray scattering (SAXS) using synchrotron radiation (SR) is an excellent tool for studying non-crystalline tissue materials. This work introduces this powerful technique to study the supra-molecular arrangement of collagen and the lipid lamellar structure from skin samples under several conditions. Healthy skin presented a characteristic collagen pattern with a series of narrow rings associated with a repeat distance of 63.4 nm in both the whole skin and the dermis layer. In the epidermis, only the lipid pattern from the organisation of the lamellar stratum corneum (SC) was visible. The SAXS patterns of samples from young subjects presented a high number of diffraction orders and marked anisotropy, most likely due to a higher degree of collagen orientation than from older subjects. The collagen peaks from skin samples with stretch marks showed a lower intensity than those from normal skin. In dermal tissue invaded by melanoma, the collagen peaks disappeared, leaving only the underlying diffuse scattering; the absence of the narrow rings indicated degradation of ordered collagen fibrils in the invaded tissue. The evaluation of collagen arrangement provides information about ageing, dysfunctions and pathology of tissue, and the systematic study of different samples results in scattering signatures characteristic of each skin layer. All in all, the potential of this methodology as a diagnostic tool for skin conditions should be considered further.