Lignin/poly(butylene succinate) composites with antioxidant and antibacterial properties for potential biomedical applications

Lignin (LIG) is a renewable biopolymer with well-known antimicrobial and antioxidant properties. In the present work LIG was combined with poly(butylene succinate) (PBS), a biocompatible/biodegradable polymer, to obtain composites with antimicrobial and antioxidant properties. Hot melt extrusion was used to prepare composites containing up to 15% (w/w) of LIG. Water contact angle measurements suggested that the incorporation of LIG did not alter the wettability of the material. The material density increased slightly when LIG was incorporated (<1%). Moreover, the melt flow index test showed an increase in the fluidity of the material (from 6.9 to 27.7 g/10 min) by increasing the LIG content. The Young's modulus and the tensile deformation of the material were practically unaffected when LIG was added. Infrared spectroscopy and differential scanning calorimeter confirmed that there were interactions between LIG and PBS. The DPPH assay was used to evaluate the antioxidant properties of the materials. The results suggested that all the materials were capable of reducing the DPPH concentrations up to 80% in <5 h. Finally, LIG-containing composites showed resistance to adherence of the common nosocomial pathogen, Staphylococcus aureus. All tested materials showed ca. 90% less bacterial adherence than PBS.