pH-responsive lignin-based complex micelles: Preparation, characterization and application in oral drug delivery

We developed a simple and practical method to prepare pH-responsive lignin-based complex micelles in green solvents using purified alkali lignin. Alkali lignin (AL) was quaternized and further self-assembled into lignin-based complex micelles with sodium dodecyl benzenesulfonate (SDBS) in an ethanol/water mixture. The FT-IR and 1H NMR spectra indicated the successful grafting of quaternary ammonium groups on AL. TEM images showed that the complex micelles were uniform spherical nanoparticles. The complex micelles also exhibited rich phase behaviors responding to pH changes. Ibuprofen (IBU) was used as a drug model and more than 74.44% could be encapsulated via hydrophobic interactions. The in vitro release behavior of IBU was pH-dependent and exhibited controlled release properties. Therefore, more than 75% of IBU could be preserved in simulated gastric fluid (SGF, pH 1.2), and over 90% could be released smoothly in simulated intestinal fluid (SIF, pH 7.4). This work suggests a novel strategy for fabricating an oral drug delivery carrier and is of significance for the value-added utilization of lignin.