Nanoindentation Derived Mechanical Properties of the Corneoscleral Rim of the Human Eye

2014 ◽  
Vol 606 ◽  
pp. 117-120 ◽  
Author(s):  
Philipp Eberwein ◽  
Jiri Nohava ◽  
Günther Schlunck ◽  
Michael Swain
Keyword(s):  
Mechanical Properties ◽  
Stem Cells ◽  
Soft Tissues ◽  
Maximum Load ◽  
Biomechanical Properties ◽  
Epithelial Stem Cells ◽  
Hold Period ◽  
Maximal Load ◽  
Region 10 ◽  
Corneoscleral Rim

The corneoscleral rim of the eye represents a region with unique anatomical properties due to its location between the cornea and sclera / conjunctiva. It further has unique functional properties due to the location of adult corneal epithelial stem cells in the rim structure (limbus) itself. These stem cells are essential for the regeneration of the corneal epithelium and for preventing the conjunctival epithelium from growing onto the corneal surface, which could result in blindness. Survival and self-renewal properties of stem cells are known to depend on specific biological and biomechanical properties of its niche environment. We therefore aimed to measure the local mechanical properties of the human corneoscleral rim using a novel nanoindentation device (Bioindenter CSM Instruments, Neuchâtel, Switzerland) developed for soft tissues evaluation. Nanoindentation was performed using a spherical indenter of 0,5mm radius, a maximal load ranging between 20 μN to 30 μN and a penetration depth of several μm to 60μm. The hold period at maximum load was 180 seconds. Youngs modulus (E) was calculated using a Hertzian fit to the loading data. E of the central cornea was in the range of 19 kPa, while in the scleral region we found 17 kPa and the limbal rim region 10 kPa. Considerable creep relaxation occurred during the hold period at maximum load, which scaled with the elastic modulus of the different structures. These results reveal biomechanical properties of the corneoscleral rim with distinct mechanical properties for the three anatomical regions.

scholarly journals Characterisation of Skin Biomechanical Properties via Experiment-Numerical Integration

2018 ◽  
Vol 7 (4.26) ◽  
pp. 205
Author(s):  
Nor Fazli Adull Manan ◽  
Linasuriani Muhamad ◽  
Zurri Adam Mohd Adnan ◽  
Mohd Azman Yahaya ◽  
Jamaluddin Mahmud
Keyword(s):  
Mechanical Properties ◽  
Constitutive Equation ◽  
Numerical Integration ◽  
Soft Tissues ◽  
Biomechanical Properties ◽  
Test Machine ◽  
Medical Sciences ◽  
Ogden Model ◽  
Hyperelastic Model ◽  
Load Displacement

By having specific mechanical properties of skin, computational program and analysis become more reliable by showing the real skin behaviour. Up to date, mechanical properties of biological soft tissues (skin) haven’t been accepted solely for official usage. Therefore, characterisation of the skin biomechanical properties might contribute a new knowledge to the engineering and medical sciences societies. This paper highlights the success in characterising the hyperelastic parameters of leporine (rabbit) skin via experimental-numerical integration. A set of five sample of leporine skin were stretched using the conventional tensile test machine to generate the load-displacement graphs. Based on the Ogden’s constitutive equation and Mooney-Rivlin hyperelastic model, a stress-stretch equation was developed and a programme was written using Matlab. By varying the Ogden’s and Mooney-Rivlin’s parameters, the programme was capable of plotting stress-stretch and load-displacement graphs. The graphs that best match the experimental results will constitut to the corresponding coefficient, µ, and α for Ogden Model and C1 and C2 material parameter for Mooney-Rivlin Model that will best describe the behaviour of the leporine skin. The current results show that the Ogden’s coefficient and exponent for the subject was estimated to be (μ = 0.048MPa, α = 7.073) & (μ = 0.020MPa, α = 9.249) for Anterior-Posterior (AP) and Dorsal-Ventral (DV) respectively for Ogden Model. Meanwhile the value for Mooney-Rivlin Model were estimated to be (C1 = 1.271, C2 = 1.868) & (C1 = 1.128, C2 = 1.537) for AP and DV respectively, which is in close agreement to results found by other researchers. Further analyses for comparison could be carried out by developing mathematical model based on other constitutive equation such as Arruda-Boyce and Neo-Hookean. Nevertheless, this study has contributed to the knowledge about skin behaviour and the results are useful for references.  

scholarly journals Biomechanical comparison of subscapularis peel and lesser tuberosity osteotomy for double-row subscapularis repair technique in a cadaveric arthroplasty model

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Mandeep S. Virk ◽  
Saleh S. Aiyash ◽  
Rachel M. Frank ◽  
Christopher S. Mellano ◽  
Elizabeth F. Shewman ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Maximum Load ◽  
Biomechanical Properties ◽  
Level Of Evidence ◽  
Double Row ◽  
Lesser Tuberosity ◽  
Bone Interface ◽  
Tendon Suture ◽  
Fresh Frozen ◽  
Cadaveric Model

Abstract Introduction Management of the subscapularis during shoulder arthroplasty is controversial. The purpose of this study was to compare the biomechanical performance of subscapularis peel (SP) and lesser tuberosity osteotomy (LTO) in a cadaveric model. Methods The subscapularis and proximal humerus were dissected from all soft tissues in 21 fresh-frozen human cadaveric shoulders and randomized to undergo SP, LTO, or standard subscapularis tenotomy (ST, control). For SP and LTO, six #5 sutures were passed through eyelets in the implant (on lateral border and through drill holes in bicipital groove [2] and under trunion [4]). Double-row repair was performed using two lateral row transosseous sutures and four medial row sutures through the tendon (SP) or osseotendinous junction (LTO). Biomechanical properties and mode of failure were tested. Results There were no significant differences in elongation amplitude, cyclic elongation, or maximum load to failure between the three groups (P > 0.05). Mean stiffness was significantly higher in LTO (P = 0.009 vs. SP and ST). In the ST group, 7/7 specimens failed at the tendon-suture interface. For SP, 4/7 failed at the tendon-suture interface, one at the suture-bone interface, one fractured around the implant stem, and one at the knots. For LTO, 3/7 failed at the tendon-suture interface, two at the suture-bone interface and two fractured around the implant stem. Conclusions In this cadaveric model, subscapularis repair via ST, SP, and LTO techniques was biomechanically equivalent. Additional studies are needed to confirm these findings and determine the influence of biologic healing on healing rates and clinical outcomes. Level of evidence N/a, biomechanical laboratory study

EFFECTS OF CULTURE PERIODS AND LOADING ON BIOMECHANICAL PROPERTIES OF SHEEP COLLAGEN FASCICLES

2014 ◽  
Vol 14 (06) ◽  
pp. 1440010
Author(s):  
AHMET C. CILINGIR
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Soft Tissues ◽  
Culture Media ◽  
Experimental Studies ◽  
Biomechanical Properties ◽  
Collagen Fibrils ◽  
Tangent Modulus ◽  
Control Group ◽  
Stress Strain

Soft tissues (e.g., tendon, skin, cartilage) change their dimensions and properties in response to applied mechanical stress/strain, which is called remodeling. Experimental studies using tissue cultures were performed to understand the biomechanical properties of collagen fascicles under mechanical loads. Collagen fascicles were dissected from sheep Achilles tendons and loaded under 1, 2, and 3 kg for 2, 4, and 6 days under culture. The mechanical properties of collagen fascicles after being loaded into the culture media were determined using tensile tester, and resultant stress–strain curves, tangent modulus, tensile strength, and strain at failure values were compared with those in a non-loaded and non-cultured control group of fascicles. The tangent modulus and tensile strength of the collagen fascicles increased with the increasing remodeling load after two days of culture. However, these values gradually decreased with the increasing culture period compared with the control group. According to the results obtained in this study, the mechanical properties of collagen fascicles were improved by loading at two days of culture, most likely due to the remodeling of collagen fibers. However, after a period of remodeling, local strains on the collagen fibrils increased, and finally, the collagen fibrils broke down, decreasing the mechanical properties of the tissue.

scholarly journals Biomechanical Properties of Bone and Mucosa for Design and Application of Dental Implants

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2845
Author(s):  
Michael Gasik ◽  
France Lambert ◽  
Miljana Bacevic
Keyword(s):  
Mechanical Properties ◽  
Dental Implants ◽  
Soft Tissues ◽  
Biomechanical Properties ◽  
Stress And Strain ◽  
Pathological Conditions ◽  
Strain Components ◽  
Mechanical Factors ◽  
Movement And Deformation ◽  
Mechanical Movement

Dental implants’ success comprises their proper stability and adherence to different oral tissues (integration). The implant is exposed to different mechanical stresses from swallowing, mastication and parafunctions for a normal tooth, leading to the simultaneous mechanical movement and deformation of the whole structure. The knowledge of the mechanical properties of the bone and gingival tissues in normal and pathological conditions is very important for the successful conception of dental implants and for clinical practice to access and prevent potential failures and complications originating from incorrect mechanical factors’ combinations. The challenge is that many reported biomechanical properties of these tissues are substantially scattered. This study carries out a critical analysis of known data on mechanical properties of bone and oral soft tissues, suggests more convenient computation methods incorporating invariant parameters and non-linearity with tissues anisotropy, and applies a consistent use of these properties for in silico design and the application of dental implants. Results show the advantages of this approach in analysis and visualization of stress and strain components with potential translation to dental implantology.

scholarly journals YAP, ΔNp63, and β-Catenin Signaling Pathways Are Involved in the Modulation of Corneal Epithelial Stem Cell Phenotype Induced by Substrate Stiffness

Cells ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 347 ◽  
Author(s):  
Ricardo M. Gouveia ◽  
Flora Vajda ◽  
Jason A. Wibowo ◽  
Francisco Figueiredo ◽  
Che J. Connon
Keyword(s):  
Stem Cells ◽  
Signaling Pathways ◽  
Biomechanical Properties ◽  
Substrate Stiffness ◽  
Future Research ◽  
Cell Phenotype ◽  
Epithelial Stem Cells ◽  
Corneal Epithelial ◽  
Proliferative Markers ◽  
Limbal Epithelial Stem Cells

Recent studies have established that the phenotype of epithelial stem cells residing in the corneal periphery (the limbus) depends on this niche’s distinct biomechanical properties. However, the signaling pathways underlying this dependency are still poorly understood. To address this issue, we investigated the effect of substrate stiffness on the migration, proliferation, and molecular phenotype of human limbal epithelial stem cells (LESCs). Specifically, we demonstrated that cells grown on collagen-based substrates with limbus-like compliance showed higher proliferation and stratification and lower migration capabilities, as well as higher levels of pro-proliferative markers Ki67 and β-Catenin, and LESC markers ΔNp63, ABCG2, and CK15. In contrast, cells on stiffer substrates lost these stem/progenitor cell markers, but instead expressed the key mechanotransduction factor YAP, as well as elevated levels of BMP4, a promotor of cell differentiation known to be negatively regulated by Wnt/β-Catenin signaling. This data allowed us to propose a new model that integrates the various molecular pathways involved in LESC response to substrate stiffness. This model will potentially be a useful guide to future research on the mechanisms underlying LESC loss following fibrosis-causing injuries.

Polypeptide-affined interpenetrating hydrogels with tunable physical and mechanical properties

2019 ◽  
Vol 7 (3) ◽  
pp. 926-937 ◽  
Author(s):  
Farshad Oveissi ◽  
Sina Naficy ◽  
Thi Yen Loan Le ◽  
David F. Fletcher ◽  
Fariba Dehghani
Keyword(s):  
Mechanical Properties ◽  
Skeletal Muscles ◽  
Soft Tissues ◽  
Physical And Mechanical Properties ◽  
Biomechanical Properties ◽  
Biomedical Devices ◽  
Mechanical Stiffness

In this study, an elastic and biocompatible hydrogel was fabricated with tunable mechanical stiffness. This type of hydrogel with unique biomechanical properties is promising for a broad range of applications in designing biomedical devices for soft tissues such as brain and skeletal muscles.

Biomechanical Properties of the Stifle Joint Lateral Collateral Ligament in Dogs

1992 ◽  
Vol 05 (04) ◽  
pp. 158-162 ◽  
Author(s):  
D. Blackketter ◽  
J Harari ◽  
J. Dupuis
Keyword(s):  
Mechanical Properties ◽  
Cruciate Ligament ◽  
Lateral Collateral Ligament ◽  
Biomechanical Properties ◽  
Fibular Head ◽  
Joint Stability ◽  
Collateral Ligament ◽  
Cranial Cruciate Ligament ◽  
Stifle Joint

Bone/lateral collateral ligament/bone preparations were tested and structural mechanical properties compared to properties of cranial cruciate ligament in 15 dogs. The lateral collateral ligament has sufficient stiffness to provide stifle joint stability and strength to resist acute overload following fibular head transposition.

A common mechanism links activities of butyrate in the colon

2017 ◽  
Author(s):  
Mohit S. Verma ◽  
Michael J. Fink ◽  
Gabriel L Salmon ◽  
Nadine Fornelos ◽  
Takahiro E. Ohara ◽  
...  
Keyword(s):  
Stem Cells ◽  
Histone Deacetylases ◽  
Biological Activities ◽  
Short Chain Fatty Acids ◽  
Common Mechanism ◽  
Epithelial Stem Cells ◽  
Degree Of Unsaturation ◽  
Structure Activity ◽  
Starting Point ◽  
New Compounds

Two biological activities of butyrate in the colon (suppression of proliferation of colonic epithelial stem cells and inflammation) correlate with inhibition of histone deacetylases. Cellular and biochemical studies of molecules similar in structure to butyrate, but different in molecular details (functional groups, chain-length, deuteration, oxidation level, fluorination, or degree of unsaturation) demonstrated that these activities were sensitive to molecular structure, and were compatible with the hypothesis that butyrate acts by binding to the Zn<sup>2+</sup> in the catalytic site of histone deacetylases. Structure-activity relationships drawn from a set of 36 compounds offer a starting point for the design of new compounds targeting the inhibition of histone deacetylases. The observation that butyrate was more potent than other short-chain fatty acids is compatible with the hypothesis that crypts evolved (at least in part), to separate stem cells at the base of crypts from butyrate produced by commensal bacteria.

Structural features and strength behavior of TRIP/TWIP steels

2020 ◽  
pp. 5-18
Author(s):  
D. V. Prosvirnin ◽  
◽  
M. S. Larionov ◽  
S. V. Pivovarchik ◽  
A. G. Kolmakov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Thermomechanical Processing ◽  
Maximum Load ◽  
Structural Features ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Structural And Functional Properties ◽  
Twip Steels ◽  
The Creation

A review of the literature data on the structural features of TRIP / TWIP steels, their relationship with mechanical properties and the relationship of strength parameters under static and cyclic loading was carried out. It is shown that the level of mechanical properties of such steels is determined by the chemical composition and processing technology (thermal and thermomechanical processing, hot and cold pressure treatment), aimed at achieving a favorable phase composition. At the atomic level, the most important factor is stacking fault energy, the level of which will be decisive in the formation of austenite twins and / or the formation of strain martensite. By selecting the chemical composition, it is possible to set the stacking fault energy corresponding to the necessary mechanical characteristics. In the case of cyclic loads, an important role is played by the strain rate and the maximum load during testing. So at high loading rates and a load approaching the yield strength under tension, the intensity of the twinning processes and the formation of martensite increases. It is shown that one of the relevant ways to further increase of the structural and functional properties of TRIP and TWIP steels is the creation of composite materials on their basis. At present, surface modification and coating, especially by ion-vacuum methods, can be considered the most promising direction for the creation of such composites.

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