Phenolic-modified bacterial nanocellulose composites with antimicrobial and antioxidant activity for implantable biomaterials

Kraft lignin (KL) and olive pomace (OP) are macromolecules abundant in phenolic compounds with significant potential in biomedical applications. Bacterial nanocellulose (BNC) is a non-toxic biodegradable biopolymer that has been demonstrated as a promising alternative for implantable materials. In this work, KL and OP extracts were incorporated into both freeze-dried and never-dried BNC samples, with thicknesses of 1 and 3 mm. To comprehend the incorporation of the KL and OP extracts onto the porous membrane, the pore size of untreated BNC was measured by porometry (197 nm). The size of KL and OP particles was below 0.3 μm 2 as observed using Scanning Transmission Electron Microscopy (SEM). The modification of BNC with these active agents was carried out through an exhaustion process, and the resulting composites were characterised using various analyses, including morphological, chemical, physical, thermal, and biological assessments. Considering the use of cranium and postcranium implants, all BNC composites demonstrated a desirable residual release, which aids to minimise cytotoxicity, while preserving biological properties. The composites exhibited antimicrobial activity, particularly the OP-based composites, showing greater effectiveness against Staphylococcus aureus (with a 3 mm freeze-dried sample, obtaining 2.5 log reduction) and MS2 (both 1 and 3 mm never-dried samples, achieving 4.2 log reduction). In addition, the antioxidant properties were confirmed, reaching a maximum of 77 and 72% for freeze-dried BNC/OP and BNC/KL, respectively. Overall, these exploratory findings highlight a strong potential for bio-based implant applications.