UCSF and UC Berkeley Joint Graduate Group in Bioengineering, University of California, Berkeley, CA 94720, United States.
J Mech Behav Biomed Mater. 2011 Oct;4(7):1540-7. doi: 10.1016/j.jmbbm.2011.02.004. Epub 2011 Feb 24.
This study investigates polyacrylamide (PA) gel as a calibration material to measure the nanomechanical compressive modulus of cartilage using nanoindentation. Both nanoindentation and unconfined compression testing were performed on PA gel and porcine rib cartilage. The equilibrium moduli measured by the two methods were discernable. Nanoindentation has the advantage of distinguishing between spatially dependent constituent properties that affect tissue mechanical function in heterogeneous and hierarchically structured tissues such as cartilage. Both sets of measurements exhibited similar positive correlation with increasing gel crosslinker concentration. The compressive modulus measurements from compression in the PA gels ranged from 300 kPa-1.4 MPa, whereas those from nanoindentation ranged from 100 kPa-1.1 MPa. Using this data, a method for relating nanoindentation measurements to conventional mechanical property measurements is presented for porcine rib cartilage. It is shown that based on this relationship, the local tissue modulus as measured from nanoindentation (1.1-1.4 MPa) was able to predict the overall global modulus of the same sample of rib cartilage (2.2 MPa), as confirmed by experimental measurements from unconfined compression. This study supports the use of nanoindentation for the local characterization of cartilage tissues and may be applied to other soft tissues and constructs.
本研究探讨了聚丙烯酰胺(PA)凝胶作为校准材料,通过纳米压痕测量软骨的纳米机械压缩模量。在 PA 凝胶和猪肋软骨上同时进行了纳米压痕和无约束压缩测试。两种方法测量的平衡模量是可区分的。纳米压痕具有区分空间相关的组成特性的优势,这些特性会影响软骨等异质和层次结构组织的组织机械功能。两组测量结果均与凝胶交联剂浓度的增加呈正相关。PA 凝胶压缩测量的压缩模量范围为 300 kPa-1.4 MPa,而纳米压痕测量的压缩模量范围为 100 kPa-1.1 MPa。使用该数据,为猪肋软骨提出了一种将纳米压痕测量值与常规力学性能测量值相关联的方法。结果表明,根据这种关系,从纳米压痕测量的局部组织模量(1.1-1.4 MPa)能够预测同一肋软骨样本的整体全局模量(2.2 MPa),这与无约束压缩的实验测量结果相符。本研究支持使用纳米压痕对软骨组织进行局部特性分析,并可应用于其他软组织和构建体。