Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia.
PLoS One. 2013 Nov 19;8(11):e81196. doi: 10.1371/journal.pone.0081196. eCollection 2013.
Nanomechanical testing methods that are suitable for a range of hydrated tissues are crucial for understanding biological systems. Nanoindentation of tissues can provide valuable insights into biology, tissue engineering and biomimetic design. However, testing hydrated biological samples still remains a significant challenge. Shark jaw cartilage is an ideal substrate for developing a method to test hydrated tissues because it is a unique heterogeneous composite of both mineralized (hard) and non-mineralized (soft) layers and possesses a jaw geometry that is challenging to test mechanically. The aim of this study is to develop a novel method for obtaining multidirectional nanomechanical properties for both layers of jaw cartilage from a single sample, taken from the great white shark (Carcharodon carcharias). A method for obtaining multidirectional data from a single sample is necessary for examining tissue mechanics in this shark because it is a protected species and hence samples may be difficult to obtain. Results show that this method maintains hydration of samples that would otherwise rapidly dehydrate. Our study is the first analysis of nanomechanical properties of great white shark jaw cartilage. Variation in nanomechanical properties were detected in different orthogonal directions for both layers of jaw cartilage in this species. The data further suggest that the mineralized layer of shark jaw cartilage is less stiff than previously posited. Our method allows multidirectional nanomechanical properties to be obtained from a single, small, hydrated heterogeneous sample. Our technique is therefore suitable for use when specimens are rare, valuable or limited in quantity, such as samples obtained from endangered species or pathological tissues. We also outline a method for tip-to-optic calibration that facilitates nanoindentation of soft biological tissues. Our technique may help address the critical need for a nanomechanical testing method that is applicable to a variety of hydrated biological materials whether soft or hard.
适用于多种水合组织的纳米力学测试方法对于理解生物系统至关重要。组织的纳米压痕可以为生物学、组织工程和仿生设计提供有价值的见解。然而，测试水合生物样品仍然是一个重大挑战。鲨鱼颌骨软骨是开发测试水合组织方法的理想基质，因为它是一种独特的矿物质化（硬）和非矿物质化（软）层的异质复合材料，并且具有难以机械测试的颌骨几何形状。本研究的目的是开发一种从单一样本中获得颌骨软骨的两个层的各向异性纳米力学特性的新方法，该样本取自大白鲨（Carcharodon carcharias）。由于该物种是受保护物种，因此获得单一样本的多向数据的方法对于检查鲨鱼的组织力学非常必要，因为获得样本可能很困难。结果表明，该方法保持了样本的水合状态，否则样本会迅速脱水。本研究首次分析了大白鲨颌骨软骨的纳米力学特性。在该物种的颌骨软骨的两个层中，在不同的正交方向上检测到纳米力学特性的变化。数据进一步表明，鲨鱼颌骨软骨的矿物质化层比以前认为的要柔软。我们的方法允许从单个小的水合异质样本中获得各向异性的纳米力学特性。因此，当标本稀有、珍贵或数量有限时，例如从濒危物种或病变组织获得的标本，我们的技术非常适合使用。我们还概述了一种用于尖端到光学校准的方法，该方法便于软生物组织的纳米压痕。我们的技术可能有助于满足对适用于各种水合生物材料（无论是软的还是硬的）的纳米力学测试方法的迫切需求。
