Phenolated lignin nanoparticles with improved stability and biofunctionality: A comparative study of...

In this study lignin was chemically modified by phenolation to investigate its application for a comparative study of nanoprecipitation and solvent exchange assisted nanoparticle fabrication to evaluate their potential for biomedical applications. Phenolation successfully incorporated phenolic hydroxyl groups onto Kraft lignin (3.65 mmol/g) and Milled wood lignin (2.10 mmol/g) quantified via ³¹P NMR and 2D-HSQCNMR. The plausible functional pathway was also studied to map the phenolic density and aromatic substitution patterns. Moreover, the characterization of the fabricated nanoparticles, revealed that nanoprecipitation produced consistent, highly stable monodisperse particles (90-160 nm, PDI < 0.1, Z.P -26 to -45 mV), while solvent exchange produced large size yet less stable nanoparticles (550-800 nm) with diverse range. The antioxidant capacity and antimicrobial activity showed that phenolated nanoparticles made by nanoprecipitation exhibited superior performance >50 μM TE/mL for DPPH and > 200 μM TE/mL for ABTS and 100 % bacterial inhibition for both gram positive (S. aureus) and gram negative (E. coli) bacterial strains. Functional assessments including cytotoxicity and hemocompatibility also revealed that both types of the nanoparticles are highly compatible to human dermal fibroblast over 24, 48 and 72 h with viable cells >90 % for phenolated Kraft lignin. Additionally, all the nanoparticles exhibited <50 % hemolytic activity even at highest concentrations confirming their acceptable hemocompatibility for biomedical applications. Overall this study supports future developments of lignin-based nanomaterials for health promoting and medicinal applications.