Effect of freezing and thawing on the biomechanical characteristics of porcine ocular tissues

Abass, Ahmed; Eliasy, Ashkan; Geraghty, Brendan; Elabd, Maher; Hassan, A.; Elsheikh, Ahmed

doi:10.1016/j.jbiomech.2019.02.024

Cited by 7 publications

(2 citation statements)

References 37 publications

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“…A further limitation was the need to freeze the tissue before testing, which was necessary for specimen preparation. A recent study found that corneal and scleral tissue experienced negligible changes in mechanical behaviour upon freezing and thawing [56], but there was no evidence that the same effect applied to the vitreous. Moreover, the vitreous parameters were estimated by tracing the displacement of points at different radii from the centre of the posterior chamber.…”

Section: Discussionmentioning

confidence: 97%

Experimental evaluation of the viscoelasticity of porcine vitreous

Aboulatta

Abass

Makarem

et al. 2021

J. R. Soc. Interface.

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This study aims to estimate the material properties of the porcine vitreous while testing it in close to its natural physiological conditions. Eighteen porcine eyes were tested within 48 h post-mortem. A custom-built computer-controlled test rig was designed to support, load and monitor the behaviour of eye globes while being subjected to dynamic rotation cycles mimicking saccade eye movement. Specimens were glued to the base of a container, surrounded by gelatin, frozen and cut in half to expose the vitreous. After thawing, the container was subjected to concentric dynamic rotations of up to 5°, 10° or 15°, while taking 50 MP photos of the specimen every 2 ms. The images were analysed by a digital image correlation algorithm to trace the movement of marked points on the vitreous surface with different radii from the centre of the posterior chamber. The initial camera image was used in building a finite-element model of the test set-up, which was used in an inverse analysis exercise to estimate the material properties of the vitreous. Angular displacements of the monitored points were up to 3.3°, 4.1° and 3.9° in response to eye rotations of 5°, 10° and 15°, respectively. With the experimental relationships between eye rotation and angular displacements used as target behaviour, the inverse analysis exercise estimated the initial shear modulus, the long-term shear modulus and the viscoelastic decay constant of the porcine vitreous as 2.10 ± 0.15 Pa, 0.50 ± 0.04 Pa and 1.20 ± 0.09 s −1 , respectively. Consideration of the viscoelasticity of the vitreous was essential to represent its experimental behaviour. Testing the vitreous in close to its normal physiological conditions produced estimations of the initial shear modulus and long-term shear modulus that were, respectively, smaller and larger than reported values (Zimberlin et al . 2010 Soft Matter 6, 3632–3635. ( doi:10.1039/b925407b ), Liu et al . 2013 J. Biomech. 46, 1321–7. ( doi:10.1016/j.jbiomech.2013.02.006) , Rossi et al . 2011 Invest. Ophthalmol. Vis. Sci. 52, 3994–4002. ( doi:10.1167/iovs.10-6477 )).

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Section: Discussionmentioning

confidence: 97%

Experimental evaluation of the viscoelasticity of porcine vitreous

Aboulatta

Abass

Makarem

et al. 2021

J. R. Soc. Interface.

Self Cite

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“…Freezing, unlike cryopreservation, not only preserves cell vitality but also maintains the mechanical properties of the analyzed tissues. Previous studies on soft materials have demonstrated that viscoelastic features remain unchanged after freezing at −80 • C for 14 days, showing no statistically significant differences [21][22][23]. Nevertheless, due to the lack of similar tests involving pancreatic tissue, we chose to compare fresh samples with those post-freezing, analyzing the same sample at identical points before and after freezing.…”

Section: Methodsmentioning

confidence: 99%

Analysis of the Mechanical Characteristics of Human Pancreas through Indentation: Preliminary In Vitro Results on Surgical Samples

Pagnanelli,

De Gaetano,

Callera

et al. 2024

Biomedicines

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Pancreatic surgery is extremely challenging and demands an extended learning curve to be executed with a low incidence of post-operative complications. The soft consistency of the human pancreas poses a primary challenge for pancreatic surgeons. This study aimed to analyze the preliminary mechanical characteristics of the human pancreas to develop a realistic synthetic phantom for surgical simulations in the near future. Pancreatic specimens, comprehensive of the pancreatic parenchyma and main pancreatic duct, were collected during pancreatic resections and analyzed through nano-bio-indentation (BioindenterTM UNHT3 Bio, Anton Paar GmbH, Graz, Austria) to measure the elastic modulus. Comparisons were made between slow and fast loading rates, immediate and post-freezing analyses, and multipoint indentations. The results demonstrated that a slow loading rate (30 μN/min), immediate analysis, and multipoint measurements are crucial for obtaining accurate values of the elastic modulus of the human pancreas (1.40 ± 0.47 kPa). In particular, the study revealed that analysis after freezing could impact the outcomes of the indentation. Moreover, the study suggested that both the pancreatic parenchyma and the main pancreatic duct should be analyzed to achieve a more precise and comprehensive definition of the. mechanical features of the pancreas. These preliminary findings represent the initial steps toward defining the consistency and mechanical characteristics of human pancreatic tissue with the goal of creating a realistic synthetic phantom.

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