Viscoelastic modeling of human colon cancer and surrounding healthy tissue using mechanical indentation

Modeling the mechanical behavior of human tissues, particularly tumor tissues, poses significant challenges due to the difficulty in acquiring samples. In this study, we performed a total of ten measurements on five freshly excised peritoneal metastasis samples, alongside ten measurements from two healthy colon samples, to develop mechanical models using the standard linear solid (SLS) model and its generalized forms. The peritoneal metastasis samples included colon cancer (2 samples), ovarian cancer (1 sample), and rectal cancer (2 samples). An ex vivo static indentation test was conducted to assess the stress relaxation behavior of both tumor and healthy tissues using a step indentation protocol. A novel cross-validation approach was employed for model selection, based on mean square error (MSE) values. Due to the irregularity and complexity of tumor tissues, 80% of the tumor measurements required more complex models with additional parameters compared to the healthy colon tissues. The five-element double Maxwell-Wiechert (DMW) arm model was suitable for describing the mechanical behavior of all healthy colon tissue measurements. In contrast, the seven-element triple Maxwell-Wiechert (TMW) arm model best described 80% of the tumor tissue measurements, while the DMW model was adequate for the remaining 20%. Further histopathological analysis of the tissue samples may help elucidate the relationship between biological composition and mechanical properties.