In vitro safety and ecotoxicity tests of suberin- and lignin-based nanoparticles

Nanoparticles from biobased raw materials can be utilised to improve functional properties of textiles and fibre-based packaging materials. Safety of chemicals need to be assessed in the EU before entering to the market. This study investigates the bioactivity and potential ecotoxicity and toxicity of biobased nanoparticles from hydrolyzed suberin (SNPs), softwood kraft lignin (lignin nanoparticles, LNPs), and tall oil fatty acid esterified softwood kraft lignin (TOFA-lignin, TOFA-LNPs). Nanoparticles were assayed as concentrations sufficient for textile coating applications for cytotoxicity, skin sensitization, corrosion, and irritation in vitro. For ecotoxicity evaluation, algal inhibition, Daphnia sp. acute immobilization, D. magna reproduction, and toxicity to earthworms were tested. Antibacterial properties were examined using recombinant Escherichia coli and Staphylococcus aureus strains, while antioxidant activities were evaluated with in vitro assays. Results indicated that nanoparticles were safe at the studied concentrations according to the cytotoxicity and skin irritation or corrosion tests. However, LNPs at concentrations of 70.31 μg/mL and TOFA-LNPs at 125 μg/mL (w/v) showed skin sensitization, unlike SNPs. Ecotoxicity assays revealed that all aqueous nanoparticle dispersions exhibited effects on algae and daphnids but were harmless to earthworms at the concentrations tested. LNPs and TOFA-LNPs showed high antibacterial and antioxidant activities, which can likely be attributed to their high total phenolic content. With structurally more complex SNPs, both antioxidant and antibacterial activities were low. The results show that the investigated nanoparticles are potential alternatives to fossil-based and more harmful chemicals. Biobased, safe-assessed alternatives for coating of textiles could be a way to increase the environmentally sustainability.