Nonlinear Elasticity in Biological Gels

Unlike most synthetic materials, biological materials often stiffen as they are deformed. This nonlinear elastic response, critical for the physiological function of some tissues, has been documented since at least the 19th century, but the molecular structure and the design principles responsible for it are unknown. Current models for this response require geometrically complex ordered structures unique to each material. In this Article we show that a much simpler molecular theory accounts for strain stiffening in a wide range of molecularly distinct biopolymer gels formed from purified cytoskeletal and extracellular proteins. This theory shows that systems of semi-flexible chains such as filamentous proteins arranged in an open crosslinked meshwork invariably stiffen at low strains without the need for a specific architecture or multiple elements with different intrinsic stiffnesses.Comment: 23 pages, 5 figures, submitted to Natur

Effect of Fibrin Glue on the Biomechanical Properties of Human Descemet's Membrane

10.1371/journal.pone.0037456PLoS ONE75

Corneal Biomechanics

The corne a is the first and mos t powe rful refrac tive surface of the optical syst em of 6 the eye. 7 The produc tion of an accur ate image in the ret inal rece ptors requires the cornea 8 to be transpa rent and have a suitabl e refractive po wer [ 1 ? 3 ]. 9 The struct ural integr ity o f the corne a can be altered in the CR modify ing its 10 refrac tive prope rties. These procedure s have been develop ed emp irically without 11 detailed kno wledge of corneal behavior . 12 Measuri ng the change in corneal shape has been available in the past d ecade 13 through com puterized analysis of the reflec tion of photo keratos copic ring surface of 14 the cornea (corneal topog rapher). 15 Little is know n about the behavio r of the internal structure of the corne a. 16 Altho ugh the ult rastructu re was analyzed by elect ron micro scopy, the rol e of each 17 one of the layers has not been examined in detail. We shall see below attempt s to 18 define such roles, which still need further anal ysis. 19 The tools to measur e and under stand these proce sses ari se from mechani cal 20 engineer ing and have been used in othe r medica l specialties , such as o rthopedics, 21 which evaluates quantitative ly the require ments of the prosthes is. Many of these 22 methods are not suitable for soft tissue such as the corne a, but the general princi ples 23 can be appl ied.Fil: Guarnieri, Fabio Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentin