A Study of Perturbations in Structure and Elastic Modulus of Bone Microconstituents Using Bimodal Amplitude Modulated-Frequency Modulated Atomic Force Microscopy

Abstract

Sepsis-related bone diseases are rarely reported although many ICU patients are diagnosed with bone damage after prolonged immobility. In this work, cortical bone of femurs from Sprague−Dawley rats under mild sepsis condition are investigated by using Scanning Probe Microscopy (SPM) to study the influence of sepsis on the changes of structure, chemistry, and elastic modulus of bone microconstituents, i.e., collagen fibers and mineral. The results show that there are significant changes on elastic modulus, shape, and chemical composition of collagen fibers 24 h after the sepsis insult, but all of the changes are recovered to almost normal 96 h after the insult. These phenomena are found to be associated with demineralization of the collagen fiber. For the mineral constituents in bone, the elastic modulus decreases significantly 96 h after the insult, showing slower responses compared with those in the collagen fibers. Particle analysis reveals that the size of the mineral particles decreases continuously and significantly with the time after the sepsis insulting. This work reveals the responding processes of bone microconstituents to sepsis in rat mode and, hence, can provide an insight into the pathogenesis of sepsis related human bone damage.

Local Mechanical Properties of Heterogeneous Nanostructures Developed in a Cured Epoxy Network: Implications for Innovative Adhesion Technology

“…The ability of the AM-FM method to quantify nanoscale mechanical properties has been well proven with various materials, including glassy and crystalline polymers, biomaterials, and metallic alloys. ,,, Figure shows several AM-FM images of different quantities that were simultaneously obtained on Epoxy1 cured at 296 K for 24 h (conversion degree of ∼81%). The surface roughness of this sample estimated from the topographic image (Figure a) was ∼0.6 nm over an area of 500 × 500 nm 2 , which was much smoother than those of fractured epoxy surfaces with roughness of a few nanometers reported in the literature. − This roughness value was also well below the indentation depth of the probe into the sample surface, that is, the deformation of the sample, which was 2.5 ± 0.2 nm, as shown in Figure b.…”

“…The AM-FM method, which was recently developed by Proksch and coworkers, ,, has been demonstrated as a powerful approach for nanomechanical characterization of structured materials at high spatial resolution. ,− In this method, the AFM probe was simultaneously excited at or near resonant frequencies of the first and second eigenmodes. The oscillation at the first resonant frequency was operated in AM mode in which the oscillation of the probe was kept constant during the interaction with the sample surface.…”

Nanomechanical mapping of soft materials with the atomic force microscope: methods, theory and applications

“…251 High-spatial resolution maps of the elastic properties of membrane proteins, 214 single proteins, 24 protein fibrils 252,253 and DNA 215,254 were generated with a lateral resolution in 1 to 5 nm range. Nanomechanical maps of other biological systems such as bone elements, 255 virus-like particles 256 and cells have been reported. 257,258 Instrumentation.…”

Fast, quantitative and high resolution mapping of viscoelastic properties with bimodal AFM

“…1,6,8,[16][17][18][19][20][21] Bimodal AFM provides a very fast, high resolution and accurate method to map the elastic properties of polymers and biomolecules. 22,23 It has been applied to determine with very high spatial resolution the elastic modulus of a large variety of materials and macromolecules such as antibodies 24 and other proteins, [25][26][27] DNA, 28,29 cells, 30,31 bone microconstituents, 32 lipid bilayers, 33,34 self-assembled monolayers, 35,36 2D materials 37 or organic semiconductor devices. 38 This technique can be operated in air or liquid.…”