Hydrothermal Treatment to Enhance Supercritical CO2 Polycaprolactone Foaming Processes for Tissue Engineering Scaffolds.

Hydrothermal treatment was investigated as a strategy to enhance the supercritical CO2 foaming process for the fabrication of polycaprolactone (PCL) scaffolds intended for tissue engineering applications. PCL samples were subjected to supercritical foaming at 300 bar and 40 °C for 60 min, combined with hydrothermal treatments performed either before or after foaming at temperatures of 70-100 °C and pressures of 10-20 bar. The effects of these treatments on scaffold morphology, porosity, and mechanical behavior were evaluated using scanning electron microscopy, micro-computed tomography, and compression testing. The results showed that hydrothermal treatment prior to foaming significantly improved scaffold porosity from 16.5% (untreated PCL) up to 57.9% while increasing pore interconnectivity (up to 156.8 throats mm-3). Conversely, post-foaming hydrothermal treatment led to pore collapse and loss of structural integrity. The pre-treated scaffolds maintained compressive moduli within 2-12 MPa, consistent with values required for bone tissue engineering. In vitro degradation in PBS revealed a moderate increase in weight loss (~10% after 90 days), indicating that the hydrothermal step slightly accelerates polymer hydrolysis without compromising stability. These findings demonstrate that combining hydrothermal pre-treatment with supercritical CO2 foaming provides a solvent-free route to tailor scaffold morphology and mechanical performance, offering a sustainable alternative for the design of bioresorbable materials in regenerative medicine.