Bioimpedance spectroscopy for characterizing volume-dependent structural changes in adipose tissue

This study establishes a proof of concept that electrical bioimpedance spectroscopy (EBS) can characterize volume-dependent structural variations in adipose tissue. This comes as a part of broader initiative to improve pharmacokinetic modeling accuracy in obese patients by providing better understanding of adipose tissue structural properties that influence drug distribution. To do so, an ex vivo porcine adipose tissue sample was subjected to a controlled progressive volume reduction, with impedance measured after each step. The data were fitted using a double Cole–Cole model to capture multiple dispersion mechanisms. The results revealed three distinct structural patterns: (1) large samples (Samples 10–9) exhibited a homogeneous structure with loosely arranged adipocytes, where conduction occurred predominantly through extracellular pathways; (2) intermediate samples exhibited transitional dielectric features reflecting the shift from fluid-rich to compact tissue organization; (3) small samples were compact and homogeneous, characterized by tightly packed adipocytes and minimal interstitial fluid. Cole–Cole parameters varied non-linearly with volume, reflecting underlying structural transitions in tissue organization. Time-domain relaxation curves reflected compartmentalization of fat tissue into fast-relaxing aqueous pathways and slow-relaxing lipid-rich domains. These findings establish that impedance-derived parameters capture structural components, including adipocyte density and interstitial fluid content, that directly influence drug distribution. This offers a pathway to integrate structural markers into pharmacokinetic frameworks.