Microstructural electromechanical coupling changes in bone under sepsis

Type I collagen fibrils are central to bone load-bearing, and their intrinsic piezoelectricity is essential for mechanotransduction and remodeling. However, how electromechanical coupling evolves during disease progression remains unclear. In this study, scanning probe microscopy (SPM) was used to quantitatively assess the mechanical and piezoelectric properties of individual type I collagen fibrils from rat cortical bone following mild sepsis. Young's modulus and piezoelectric amplitude were measured at defined postoperative time points to track temporal changes. Results showed a biphasic mechanical response, with Young's modulus decreasing initially and then recovering, while the piezoelectric response exhibited an opposite trend. Both parameters displayed clear inflection points at 48 h post-surgery. At this stage, fibrils also showed reduced diameter, shortened D-periodicity, and decreased mechanical heterogeneity. These findings reveal a time-dependent decoupling of electromechanical behavior in septic bone, providing microscale insights into bone pathophysiology with potential implications for early diagnosis and intervention.