AFM-Based Method for Measurement of Normal and Osteoarthritic Human Articular Cartilage Surface Roughness

Abstract

In osteoarthrosis, pathological features of articular cartilage are associated with degeneration and nanomechanical changes. The aim of this paper is to show that indentation-atomic force microscopy can monitor wear-related biomechanical changes in the hip joint of patients with osteoarthritis. Fifty patients (N = 50), aged 40 to 65, were included in the study. The mechanical properties and the submicron surface morphology of hyaline cartilage were investigated using atomic force microscopy. Measurements of the roughness parameters of cartilage surfaces were performed, including the arithmetic average of absolute values (Ra), the maximum peak height (Rp), and the mean spacing between local peaks (S). The arithmetic mean of the absolute values of the height of healthy cartilage was 86 nm, while wear began at Ra = 73 nm. The maximum changes of values of the roughness parameters differed from the healthy ones by 71%, 80%, and 51% for Ra, Rp, and S, respectively. Young’s modulus for healthy cartilage surfaces ranged from 1.7 to 0.5 MPa. For the three stages of cartilage wear, Young’s modulus increased, and then it approached the maximum value and decreased. AFM seems to be a powerful tool for surface analysis of biological samples as it enables indentation measurements in addition to imaging.

Nanomechanical Properties of Articular Cartilage Due to the PRP Injection in Experimental Osteoarthritis in Rabbits

“…It was observed that each 60 μm change in indenter location could result in a twentyfold variation of the measurement [ 66 ]. Our previous research carried out to 450 nm in depth [ 67 ] shows that the surface is more suitable to diagnose, so in this study, we measured the mechanical properties of cartilage surface to 150 nm in depth. However, the statistical significance of the results was observed below 100 nm.…”

“…Past studies of articular cartilage have assumed a wide range of Poisson’s ratios [ 63 , 64 ]. In this study [ 67 ], the local Poisson’s ratio was assumed to be 0.5 for articular cartilage based on previous experimental reports. The changes in articular cartilage structure result in deterioration of the mechanical strength [ 60 ].…”

“…The equations for calculation of Young’s modulus from cantilever deflection data was derived using a linear model of interacting cantilever spring and elastic surface in conditions for quasi-static equilibrium presented as equality of cantilever spring forces exerted and elastic surface response [ 67 ]: where k is stiffness of the cantilever, and P(h) is normal load as a function of variable indentation depth. The penetration of the probe h into articular cartilage is presented by Equation (2) and in Figure 3 [ 67 ]: where h is the penetration of the probe into cartilage, is the bend of the console, and is the displacement of the console along the vertical axis.…”

Early Detection of Cartilage Degeneration: A Comparison of Histology, Fiber Bragg Grating-Based Micro-Indentation, and Atomic Force Microscopy-Based Nano-Indentation

“…In a recent study we have demonstrated that by scanning the FBG sensor across a sample surface, it is indeed capable of detecting and quantifying elasticity gradients of the sample [ 22 ]. In addition, our results emphasize that the FBG sensor is potentially able to detect early OA even before the surface roughness of the cartilage is increased due to wear-related changes, which is crucial for other AFM-based approaches to detect the onset of OA [ 35 ].…”

Precision 3D‐Printed Cell Scaffolds Mimicking Native Tissue Composition and Mechanics

“…Bioprinting seeks to replicate the broad range of stiffnesses exhibited in native tissues, as for example the lung (0.2-2 kPa) and cartilage (500-1700 kPa). [41,42] Various biofabrication techniques have achieved these mechanical properties using gelatin and its derivatives. [35,43] To realize an equally broad spectrum of mechanical properties in TPS printed ECM derived scaffolds would hence be highly desirable.…”