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

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.