Urinary Bladder vs Gastrointestinal Tissue: A Comparative Study of Their Biomechanical Properties for Urinary Tract Reconstruction.

OBJECTIVE: To evaluate the mechanical properties of gastrointestinal (GI) tissue segments and to compare them with the urinary bladder for urinary tract reconstruction. METHODS: Urinary bladders and GI tissue segments were sourced from porcine models (n = 6, 7 months old [5 male; 1 female]). Uniaxial planar tension tests were performed on bladder tissue, and Cauchy stress-stretch ratio responses were compared with stomach, jejunum, ileum, and colonic GI tissue. RESULTS: The biomechanical properties of the bladder differed significantly from jejunum, ileum, and colonic GI tissue. Young modulus (kPa-measure of stiffness) of the GI tissue segments was on average 3.07-fold (±0.21 standard error) higher than bladder tissue (P < .01), and the strain at Cauchy stress of 50 kPa for bladder tissues was on average 2.27-fold (±0.20) higher than GI tissues. There were no significant differences between the averaged stretch ratio and Young modulus of the horizontal and vertical directions of bladder tissue (315.05 ± 49.64 kPa and 283.62 ± 57.04, respectively, P = .42). However, stomach tissues were 1.09- (±0.17) and 0.85- (±0.03) fold greater than bladder tissues for Young modulus and strain at 50 kPa, respectively. CONCLUSION: An ideal urinary bladder replacement biomaterial should demonstrate mechanical equivalence to native tissue. Our findings demonstrate that GI tissue does not meet these mechanical requirements. Knowledge on the biomechanical properties of bladder and GI tissue may improve development opportunities for more suitable urologic reconstructive biomaterials.

Mechanical, biological and structural characterization of human atherosclerotic femoral plaque tissue.

The failure of endovascular treatments of peripheral arterial disease represents a critical clinical issue. Specialized data are required to tailor such procedures to account for the mechanical response of the diseased femoral arterial tissue to medical device deployment. The purpose of this study is to characterize the mechanical response of atherosclerotic femoral arterial tissue to large deformation, the conditions typical of angioplasty and stenting, and also to determine the mechanically induced failure properties and to relate this behaviour to biological content and structural composition using uniaxial testing, Fourier transform infrared spectroscopy and scanning electron microscopy. Mechanical and biological characterization of 20 plaque samples obtained from femoral endarterectomy identified three distinct classifications. "Lightly calcified" samples display linear mechanical responses and fail at relatively high stretch. "Moderately calcified" samples undergo an increase in stiffness and ultimate strength coupled with a decrease in ductility. Structural characterization reveals calcified nodules within this group that may be acting to reinforce the tissue matrix, thus increasing the stiffness and ultimate strength. "Heavily calcified" samples account for the majority of samples tested and exhibit significantly reduced ultimate strength and ductility compared to the preceding groups. Structural characterization of this group reveals large areas of calcified tissue dominating the failure cross-sections of the samples. The frequency and structural dominance of these features solely within this group offers an explanation as to the reduced ultimate strength and ductility and highlights the need for modern peripheral endovascular devices to account for this behaviour during novel medical device design.