Monitoring Porosity and Swelling Ratio of Scaffolds With Electrical Conductivity

A scaffold is a frame structural material used in tissue engineering serving for cellular adhesion, migration, proliferation, and tissue regeneration. Porosity and swelling ratio are indicators that are commonly used to determine scaffold characteristics and obtained by measuring the weight and volume of scaffolds after soaking liquid. Although the weight and volume change over time, the measurements are usually conducted once. The accuracy of both indicators is also influenced by scaffold degradation; however, the commencement of the degradation is difficult to know. In this study, the relation of porosity and swelling ratio to swollen scaffold conductivity, which is beneficial for long-term monitoring, is proposed. Sets of compositions for fabricating scaffolds were used to provide a wide-range porosity (20%–100%), swelling ratio (2–16 times), and degradation rates. A probe was developed for local conductivity measurement with an excitation frequency of 2–50 kHz. The correlation between the conductivity and the porosity was high (0.79–0.81), and that between the conductivity and the swelling ratio was higher (0.87). When the degradation occurred, the porosity and the swelling ratio became inaccurate, but the conductivity was still reliable and reflective. Mathematical models to convert the conductivity to the porosity and the swelling ratio were also proposed, where the estimation standard error (SE) was ~2% for porosity and ~0.2 times for swelling ratio estimation.