Hydrothermal Pretreatment Plus Supercritical CO2 Foaming as a Novel Route to Improving Polymer Structures for Biomedical Applications—Part 1: Preliminary Screening for Individual and Combined Polymers

Degradable polymers are essential in tissue engineering due to their capacity to mimic the extracellular matrix and promote regeneration. To be functional, they require interconnected porous structures that allow for nutrient exchange and cell migration. Although methods exist to optimize porosity, many compromise biocompatibility because pore-forming substances are used. In this context, hydrothermal pretreatment emerges as a promising technique to simultaneously improve both the porosity and mechanical properties of polymers without using potentially toxic reagents. This study proposes a novel route that combines hydrothermal pretreatment with supercritical CO₂ foaming, evaluating whether the structures obtained present better characteristics for biomedical applications compared to those obtained using supercritical CO₂ foaming alone. A screening of this novel route has been tested on individual polymers (PCL, PLA, PLGA, PVA, PBS, chitosan) and various binary combinations (PCL-PBS, chitosan-PBS, PVA-PBS, PLGA-PEDOT: PSS). The resulting materials were characterized using electron microscopy to analyze pore diameter and distribution, as well as structural stability and homogeneity. For the individual polymers, the hydrothermal pretreatment clearly improved the results obtained. However, most polymer combinations showed drawbacks such as mass losses, heterogeneity, or unsatisfactory pore formation. This research highlights the potential of hydrothermal pretreatment to optimize scaffolds, which is crucial for viability in biomedical applications.