Biomedical Engineering Seminar: Atomic Force Microscopy Measurement of Fluid-Solid Interactions within Aggrecan Proteoglycan Networks
Building 193, Electrical and Electronic Engineering
T: (03) 8344 6606
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The molecular structure and nanomechanical properties of aggrecan monomers extracted and purified from human articular cartilage from donors of different ages have recently been visualized and quantified via atomic force microscopy (AFM)-based imaging, force spectroscopy, and high bandwidth nano-rheology. AFM imaging enabled direct comparison of full length monomers at different ages. The demonstrably shorter glycosaminoglycan (GAG) chains observed in adult full length aggrecan monomers, compared to newborn monomers reflects markedly altered biosynthesis with age. These results provide molecular-level evidence of the effects of age on the conformational and nanomechanical properties of aggrecan, with direct implications for the effects of aggrecan nanostructure on macro-level properties of cartilage tissue. The presenter will discuss recent studies of brush layers of aggrecan from these same different aged human donors and, utilizing a new high frequency AFM-based rheology system, quantify their dynamic deformational behavior. The magnitude and phase angle of the dynamic stiffness showed frequency-dependent trends remarkably similar to those of intact native cartilage tissue. These techniques have thereby enabled the measurement of the hydraulic permeability of aggrecan networks, and strongly suggest that aggrecan is the key molecule in determining the fluid-flow-dependent properties of healthy cartilaginous tissues.