Porous yet dense matrices: using ice to shape collagen 3D cell culture systems with increased physiological relevance.

Standard in vitro cell cultures are one of the pillars of biomedical sciences. However, there is increasing evidence that 2D systems provide biological responses that are often in disagreement with in vivo observations, partially due to limitations in reproducing the native cellular microenvironment. 3D materials that are able to mimic the native cellular microenvironment to a greater extent tackle these limitations. Here, we report Porous yet Dense (PyD) type I collagen materials obtained by ice-templating followed by topotactic fibrillogenesis. These materials combine extensive macroporosity, favouring the cell migration and nutrient exchange, as well as dense collagen walls, which mimic locally the extracellular matrix. When seeded with Normal Human Dermal Fibroblasts (NHDFs), PyD matrices allow for faster and more extensive colonisation when compared with equivalent non-porous matrices. The textural properties of the PyD materials also impact cytoskeletal and nuclear 3D morphometric parameters. Due to the effectiveness in creating a biomimetic 3D environment for NHDFs and the ability to promote cell culture for more than 28 days without subculture, we anticipate that PyD materials could configure an important step towards in vitro systems applicable to other cell types and with higher physiological relevance.