Ecofriendly Fabrication and Hierarchical Exploration of Cytocompatible Lignin Nanoparticles for Biomedical Applications

Lignin, the most abundant renewable aromatic biopolymer, offers significant potential for bionanomaterial innovation in biomedical applications. This study presents a facile method for isolating soda lignin from waste coconut shells, followed by its standard characterizations and the design of lignin nanoparticles (LNPs) using a greener approach. A hierarchical exploration of the LNPs was performed, encompassing structural and molecular characterizations, <i>in vitro</i> enzymatic as well as cellular studies, <i>in vivo</i> assays using <i>Drosophila melanogaster</i> (<i>D. melanogaster</i>) as a model organism, <i>in silico</i> molecular docking, and molecular dynamics simulations. The resulting LNPs exhibited well-defined nanostructures with an average hydrodynamic diameter (<i>D</i>_H) of 86.59 ± 2.6 nm (DLS measurement), a spherical morphology (∼55 nm from FESEM measurement), hollow nanoarchitecture (pore diameter ∼60 nm), high colloidal stability (zeta potential: -41.1 ± 1.1 mV), and a broad emission spectrum (270-600 nm). Additionally, advanced techniques such as micro-FTIR, micro-Raman, XRD (X-ray diffraction), and TGA-DSC studies further validated the successful LNP synthesis and structural integrity. <i>In vitro</i> and <i>in vivo</i> bioactivity studies with <i>D. melanogaster</i> demonstrated that LNPs significantly outperform bulk lignins in terms of antidiabetic, antioxidant, and cytotoxicity properties. <i>In silico</i> molecular docking and molecular dynamics simulation studies supported these findings. The <i>in vitro</i> antidiabetic assay showed inhibition activities of 53.27 ± 1.3% (α-amylase) and 66.23 ± 1.5% (α-glucosidase) at 10 μg/mL, similar to the standard inhibitor acarbose. The LNPs exhibited strong antioxidant activity (56.6 ± 0.6% at 10 μg/mL), comparable to allopurinol (77.33 ± 1.4%). Along with this, LNPs displayed enhanced catalase activity (1.2-fold), reduced ROS levels (0.3-fold at 1 μg/mL), maintained glutathione levels, and did not increase H₂O₂ levels that might induce oxidative stress. MTT assays confirmed good biocompatibility in HCT cells, while <i>in vivo</i> acute toxicity studies with <i>D. melanogaster</i> indicated higher survivorship than bulk lignins.