Amino Acid-Modified Lignin Combined with Methylation to Form Novel pH-Responsive Colloidal Spheres with Tunable Properties

This study addresses the challenge of pH-triggered charge reversal nanoparticles (pH-CRNPs), focusing on enhancing their precision and scalability for widespread use. Leveraging the unique properties of lignin, a renewable aromatic macromolecule abundant in plants, we developed lignin nanoparticles (LNPs) through chemical modification with various amino acids followed by methylation in one pot. Methylation partially sealed negative charges, enhancing hydrophobicity, and enabled self-assembly into colloidal spheres with pH responsiveness under alkaline conditions. This innovative approach overcomes the limitations of weak positive charges in conventional LNPs, expanding their application beyond highly acidic tissues. Comprehensive studies explored the relationship between the molecular structure and colloidal sphere stability. Notably, the reagents used exhibited low toxicity, positioning these LNPs as promising candidates for drug delivery with simplified purification steps. This research contributes to the advancement of green synthesis strategies, making LNPs more accessible and efficient for diverse biomedical applications.