Distribution of Youngs Modulus in Porcine Corneas after Riboflavin-UVA-Induced Collagen Cross-Linking as Measured by Atomic Force MicroscopyReportar como inadecuado




Distribution of Youngs Modulus in Porcine Corneas after Riboflavin-UVA-Induced Collagen Cross-Linking as Measured by Atomic Force Microscopy - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Riboflavin-UVA-induced corneal collagen cross-linking has become an effective clinical application to treat keratoconus and other ectatic disorders of the cornea. Its beneficial effects are attributed to a marked stiffening of the unphysiologically weak stroma. Previous studies located the stiffening effect predominantly within the anterior cornea. In this study, we present an atomic force microscopy-derived analysis of the depth-dependent distribution of the Young-s modulus with a depth resolution of 5 µm in 8 cross-linked porcine corneas and 8 contralateral controls. Sagittal cryosections were fabricated from every specimen and subjected to force mapping. The mean stromal depth of the zone with effective cross-linking was found to be 219±67 µm. Within this cross-linked zone, the mean Young-s modulus declined from 49±18 kPa at the corneal surface to 46±17 kPa, 33±11 kPa, 17±5 kPa, 10±4 kPa and 10±4 kPa at stromal depth intervals of 0–50 µm, 50–100 µm, 100–150 µm, 150–200 µm and 200–250 µm, respectively. This corresponded to a stiffening by a factor of 8.1 corneal surface, 7.6 0–50 µm, 5.4 50–100 µm, 3.0 100–150 µm, 1.6 150–200 µm, and 1.5 200–250 µm, when compared to the Young-s modulus of the posterior 100 µm. The mean Young-s modulus within the cross-linked zone was 20±8 kPa 2.9-fold stiffening, while it was 11±4 kPa 1.7-fold stiffening for the entire stroma. Both values were significantly distinct from the mean Young-s modulus obtained from the posterior 100 µm of the cross-linked corneas and from the contralateral controls. In conclusion, we were able to specify the depth-dependent distribution of the stiffening effect elicited by standard collagen cross-linking in porcine corneas. Apart from determining the depth of the zone with effective corneal cross-linking, we also developed a method that allows for atomic force microscopy-based measurements of gradients of Young-s modulus in soft tissues in general.



Autor: Jan Seifert , Christian M. Hammer , Johannes Rheinlaender, Saadettin Sel, Michael Scholz, Friedrich Paulsen, Tilman E. Schäffer

Fuente: http://plos.srce.hr/



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