Antioxidant cellulose nanofibers/lignin-based aerogels: a potential material for biomedical applications

Background Lignin is a naturally occurring and aromatic biopolymer with well-known antimicrobial and antioxidant properties. Thus, in this work, the use of cellulose nanofibers (CNF) and lignin to produce ultra-light aerogels for biomedical applications was studied. Aerogels containing varying amounts of lignin (0–30 wt%) and different concentrations of the crosslinking agent Fe 3+ (25–100 mM) were developed. Results The different bioaerogels were fully characterized and their physical, mechanical and bioactive properties analyzed. It was observed that the bioaerogels soluble fraction tends to decrease as the lignin content increases for the different Fe 3+ concentrations, due to lignin–CNF interactions through hydrogen bonds. The bioaerogels containing lignin showed remarkable radical scavenging activity as the DPPH concentration decreased with time. This confirms the benefits of including lignin in bioaerogels to impart antioxidant properties. To study the suitability of the produced bioaerogels for controlled drug release, the release of tetracycline (TC) was studied. All of the bioaerogels released TC in a sustained manner for 6 h and presented similar profiles. However, the bioaerogels containing higher concentrations of crosslinker showed a higher release of TC. The TC loading conferred clear antimicrobial activity against S. aureus as expected, unlike the insignificant antimicrobial activity of the bioaerogels without TC. The biocompatibility of the samples was demonstrated for all materials produced (with and without TC loading) by the Kruskal–Wallis test with multiple comparisons. After observation of cell morphology, no significant differences were evident suggesting that the CNF–lignin bioaerogels present optimal biocompatibility for use in the biomedical and pharmaceutical industry. Conclusions The CNF–lignin bioaerogels presented in this work highlights their promising application as biomedical applications, such as wound dressings due to their biocompatibility, antimicrobial and antioxidant properties, as well as their swelling and solubility properties. Graphical Abstract