Surface chemistry and bioactivity of colloidal particles from industrial kraft lignins

The morphology control of lignin through particle size reduction to nanoscale seems to be a suitable conversion technology to overcome the intrinsic limitations of its native form to develop a wide range of biomaterials with high performance. Colloidal lignin particles (CLPs) in the range of 150-200 nm were synthesised from hardwood and softwood kraft lignins by the solvent shifting method. The initial molecular features of kraft lignins were evaluated in terms of purity, molecular weight distribution, and chemical functionalities. The impact of the lignin source and structure on the morphology, size distribution, and surface chemistry of CLPs was evaluated by particle size analyser, SEM, TEM and H-1 NMR. The results evidenced the influence of the botanical origin on the morphology and surface chemistry of particles. Furthermore, the antioxidant properties and cytotoxicity of lignins and corresponding CLPs, towards lung fibroblast cells were compared. CLPs from hardwood kraft lignins exhibited higher antioxidant power against DPPH free radical and a higher cytotoxic effect (IC30 = 67-70 mu g/mL) against lung fibroblast when compared to CLPs from softwood kraft lignin (IC30 = similar to 91 mu g/mL). However, the cytotoxicity of these biomaterials was dose-dependent, suggesting their potential application as active ingredients in cosmetic and pharmaceutic products at low concentrations.

Automated summary

By converting lignin into colloidal particles at the nanoscale, it is possible to develop a wide range of high-performance biomaterials. Colloidal lignin particles synthesized from hardwood kraft lignins showed higher antioxidant power and cytotoxicity against lung fibroblast cells compared to softwood kraft lignin-derived CLPs. The dose-dependent cytotoxicity of these biomaterials suggests their potential applications in cosmetic and pharmaceutical products at low concentrations.