Microindentation test for assessing the mechanical properties of cartilaginous tissues

Abstract

Mechanical properties of the fresh control, frozen, and vitrified cartilaginous (cartilage and meniscus) samples were measured by microindentation. Indentation depth, elastic modulus, and indentation yield strength were obtained from the microindentation loading curves. Indentation deformation behavior was studied using Hertz contact model. The stress distribution of cartilaginous tissues under indentation loading was analyzed by finite element technique. It was found that fresh tissue shows the lowest indentation depth and the highest elastic modulus and indentation yield strength, followed by vitrified and frozen tissues. The vitrified tissue shows slightly lower but comparable mechanical properties with control tissue. The vitrification technique used in this study can preserve live cells with superior mechanical properties that make it an ideal technique for use in orthopedic and other biomedical applications. The microindentation tests and corresponding analysis methods used in this study offer a simple way to evaluate the mechanical properties of cartilaginous tissues. It suits small sample sizes and it may be used for other biological tissues.

Fibrous Scaffolds with Varied Fiber Chemistry and Growth Factor Delivery Promote Repair in a Porcine Cartilage Defect Model

“…Moreover, although samples were frozen and thawed before testing, multiple groups have reported that freeze-thawing does not significantly impact mechanical properties of cartilage and other tissues in most cases, 45,46 and the values we calculated from our normal tissue samples were similar to those reported previously in literature. 35,47 Although not statistically significant, there were trends between the scaffold groups, with the sustained presence of HA (i.e., MeHA group) and the inclusion of TGFb3 in the PCL/HA composite scaffold generally resulting in higher moduli. It is important to note that these trends may have reached statistical significance with longer term studies, as 12 weeks is still a relatively short time period for cartilage repair.…”

“…Indentation was applied at 0.1%/s strain ramp for 50 s. Resulting data were then fit using a Hertz model to obtain the Young's modulus (n = 7-10). 34,35 After mechanical testing, samples were fixed in 4% paraformaldehyde and imaged by microcomputed tomography (microCT; Scanco Viva CT75), with and without an iodine-based contrast solution (Lugol solution; Sigma), as in Fisher et al 27 Finally, samples were decalcified, processed for histology, and stained using Safranin-O/Fast Green, H&E, and immunohistochemistry for type 2 collagen (n = 7-10). Four blinded independent observers scored the resulting histology, using a modified version of the ICRS-II scoring system, 36 and images were quantified for percent stained area and staining intensity, as described in the following section.…”

Degradation of silicone rubber under compression in a simulated PEM fuel cell environment

“…Microindentation load-indentation depth data contains much information from which mechanical properties such as elastic modulus can be determined [24,25]. Fig.…”

Degradation Characteristics of Elastomeric Gasket Materials in a Simulated PEM Fuel Cell Environment

“…Hertz contact theory was often used to obtain the elastic modulus from the indentation load-indentation depth curves ( Ref 30,31). Based on the Hertz theory of elastic contact, considering the contact between a rigid sphere (the indenter tip) and a flat surface (the silicone rubber sample), the relationship between the total displacement of both the indenter and sample, d, and the load P can be written as (Ref 30)…”