Development of polycaprolactone scaffold with antibacterial activity by an integrated supercritical extraction and impregnation process

• Usnea extracts isolated by using supercritical fluid technology showed strong antibacterial activity.
• Polycaprolactone (PCL) scaffolds for tissue engineering can be produced at 35 °C and 15–17 MPa of CO2 by foaming.
• An integrated process at high pressure for extraction/impregnation/foaming of PCL was developed.
• Screening of antibacterial activity of functionalized PCL against L. innocua and Methicillin-resistant Staphylococcus aureus (MRSA) strains were made.

The present study is aimed to develop a process for production of functionalized scaffolds impregnated with natural compounds extracted from Patagonian Usnea lichen. A setup for an integrated supercritical CO2 extraction of natural compounds with posterior impregnation on solid matrices (polycaprolactone, PCL) is developed and presented here. In order to establish optimized operating conditions, supercritical extraction of Usnea as well as sorption kinetics and resulting material properties have been studied separately first. Usnea extracts isolated by supercritical carbon dioxide at 30 MPa and 40 °C have shown strong antibacterial activity with values of the minimum inhibitory concentration (MIC) ranging from less than 1.25 μg/mL to 320 μg/mL against Listeria innocua and Methicillin-resistant Staphylococcus (MRS) strains. Useful scaffolds of PCL for tissue engineering containing a porous structure with pore diameters between 150 and 340 μm can be obtained when PCL is exposed to carbon dioxide at 35 °C and 15 MPa. The degree of crystallinity of functionalized PCL was shown to be influenced by the incorporated antibacterial agent. The presented results showed that the impregnated PCL samples are promising bactericidal compounds against L. innocua. Screening of antibacterial activity of functionalized PCL against a Methicillin-resistant Staphylococcus aureus (MRSA) strain showed a higher activity when a low bacterial inoculum level (2 × 104 Colony-forming Units/mL [CFU/mL]) was assayed.

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