Time dependent degradation of vitreous gel under enzymatic reaction: Polymeric network role in fluid properties

Rangchian, Aysan; Hubschman, Jean‐Pierre; Kavehpour, H. Pirouz

doi:10.1016/j.jbiomech.2020.109921

Cited by 5 publications

(6 citation statements)

References 48 publications

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“…Recent attempts to measure the undissected vitreous utilize volume-controlled cavity expansion, cavitation rheology, and creep testing with a submerged rotating rheometric head or microprobes. 13,14,22,26,32,159 Volume-controlled cavity expansion is a needle-based technique that employs a large deformation viscoelastic model to capture a material response measured after several cycles of expansion-relaxation at controlled stretch rates in a cavity expansion setting. 159 Similarly, cavitation rheology involves inserting a syringe needle into a vitreous sample and inducing an elastic instability via slow pressurization that correlates with the local mechanical properties of the sample.…”

Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

“…32 In situ rheological creep tests, in which a rotating rheometric head is submerged into the vitreous chamber, were recently used to measure the changes in the mechanical behavior of the vitreous after degradation using collagenase. 13,14 Minimally invasive rheological tests of the vitreous humor have also been attempted using microprobes controlled magnetically or optically. 22,26 While still relatively invasive (an opening has to be made in the sclera for the insertion of cavitating needle, rheometric head, silica or magnetic beads, etc.…”

Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

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Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Tram

Maxwell

Swindle-Reilly

2020

Current Eye Research

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Research on the vitreous humor and development of hydrogel vitreous substitutes have gained a rapid increase in interest within the past two decades. However, the properties of the vitreous humor and vitreous substitutes have yet to be consolidated. In this paper, the mechanical properties of the vitreous humor and hydrogel vitreous substitutes were systematically reviewed. The number of publications on the vitreous humor and vitreous substitutes over the years, as well as their respective testing conditions and testing techniques were analyzed. The mechanical properties of the human vitreous were found to be most similar to the vitreous of pigs and rabbits. The storage and loss moduli of the hydrogel vitreous substitutes developed were found to be orders of magnitude higher in comparison to the native human vitreous. However, the reported modulus for human vitreous, which was most commonly tested in vitro, has been hypothesized to be different in vivo. Future studies should focus on testing the mechanical properties of the vitreous in situ or in vivo. In addition to its mechanical properties, the vitreous humor has other biotransport mechanisms and biochemical functions that establish a redox balance and maintain an oxygen gradient inside the vitreous chamber to protect intraocular tissues from oxidative damage. Biomimetic hydrogel vitreous substitutes have the potential to provide ophthalmologists with additional avenues for treating and controlling vitreoretinal diseases while preventing complications after vitrectomy. Due to the proximity and interconnectedness of the vitreous humor to other ocular tissues, particularly the lens and the retina, more interest has been placed on understanding the properties of the vitreous humor in recent years. A better understanding of the properties of the vitreous humor will aid in improving the design of biomimetic vitreous substitutes and enhancing intravitreal biotransport.

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Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

Section: The Need For In Vivo Measurements Of the Vitreous Humormentioning

confidence: 99%

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Tram

Maxwell

Swindle-Reilly

2020

Current Eye Research

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“…When collagenase was injected to the vitreous body, the fibrillar backbone of the vitreous body was digested [ 8 ], then broken down [ 74 ]. The structure was easier to elastically deform due to fewer bonds present in the network of collagen [ 25 ]. Additionally, the values of C 10 in the 48 h liquefaction group were the lowest, probably because the natural degradation of the vitreous bodies that occurred after the eyeball was removed for over 24 h [ 25 ], which aggravated the liquefaction of the vitreous bodies.…”

Section: Discussionmentioning

confidence: 99%

“…The elastic modulus and surface tension value of the local vitreous body in eye and in vitro were determined by a technology of cavitation induction [ 23 ]. The vitreous body with almost intact structures and surrounding tissues was tested by the rheometer with a self-devised probe [ 25 ]. Viscoelasticity of the vitreous body was measured by tracing intraocular microprobes while the magnetic force was applied [ 26 ].…”

Section: Introductionmentioning

confidence: 99%

An Inverse Method to Determine Mechanical Parameters of Porcine Vitreous Bodies Based on the Indentation Test

Zhang

et al. 2023

Bioengineering

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The vitreous body keeps the lens and retina in place and protects these tissues from physical insults. Existing studies have reported that the mechanical properties of vitreous body varied after liquefaction, suggesting mechanical properties could be effective parameters to identify vitreous liquefaction process. Thus, in this work, we aimed to propose a method to determine the mechanical properties of vitreous bodies. Fresh porcine eyes were divided into three groups, including the untreated group, the 24 h liquefaction group and the 48 h liquefaction group, which was injected collagenase and then kept for 24 h or 48 h. The indentation tests were carried out on the vitreous body in its natural location while the posterior segment of the eye was fixed in the container. A finite element model of a specimen undertaking indentation was constructed to simulate the indentation test with surface tension of vitreous body considered. Using the inverse method, the mechanical parameters of the vitreous body and the surface tension coefficient were determined. For the same parameter, values were highest in the untreated group, followed by the 24 h liquefaction group and the lowest in the 48 h liquefaction group. For C10 in the neo-Hookean model, the significant differences were found between the untreated group and liquefaction groups. This work quantified vitreous body mechanical properties successfully using inverse method, which provides a new method for identifying vitreous liquefactions related studies.

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“…By contrast, hydrogel-based vitreous substitutes offer the required properties due to their similarity to the natural vitreous body. Here, the design of vitreous substitutes is supported by recent scientific findings, for example the structure of vitreous main polymers by enzymatic degradation studies [22], the behaviour of hydrogels in the presence of simulated vitreous haemorrhage [23] or the comparison of fluidic viscosity and surface tension on the tamponading effect [24].…”

Section: Requirements For Vitreous Substitutesmentioning

confidence: 96%

Novel vitreous substitutes: the next frontier in vitreoretinal surgery

Schulz

Januschowski

Szurman

2021

Current Opinion in Ophthalmology

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Purpose of reviewAfter removing the native vitreous during vitreoretinal surgery, an adequate substitute is required to ensure homeostasis of the eye. Current clinically used endotamponades (silicone oil, gases, semifluorinated alkanes) are effective in promoting retinal reattachment, but lead to complications such as emulsification, prolonged inflammation, blurred vision, raised intraocular pressure, cataract formation or the need for revision surgery. The aim of this review is to provide an update on novel vitreous substitutes with a focus on polymer-based systems. Recent findingsPolymeric hydrogels provide favourable properties such as high water content, optical transparency, suitable refractive indices and densities, adjustable rheological properties, injectability, biocompatibility and their ability to tamponade the retina via viscosity and swelling pressure, comparable to the native human vitreous body. Here, vitreous replacement strategies can be divided into chemically or physically crosslinked hydrogel systems that are applied as preformed or in-situ gelling matrices. SummarySeveral hydrogel-based vitreous substitutes have already been positively evaluated in preclinical tests and have the potential to enter the clinical phase soon.

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Time dependent degradation of vitreous gel under enzymatic reaction: Polymeric network role in fluid properties

Cited by 5 publications

References 48 publications

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

An Inverse Method to Determine Mechanical Parameters of Porcine Vitreous Bodies Based on the Indentation Test

Novel vitreous substitutes: the next frontier in vitreoretinal surgery

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