Morphology-Controlled Synthesis of Lignin Nanocarriers for Drug Delivery and Carbon Materials

Abstract

Lignin is an abundant biopolymer that is mainly burned for energy production today. However, using it as a polyfunctional macromolecular building block would be desirable. Herein, Kraft lignin was modified through esterification of its hydroxyl groups with methacrylic anhydride. Then lignin nanocarriers with different morphologies (solid nanoparticles, core–shell structures, porous nanoparticles) were produced by a combination of miniemulsion polymerization and a solvent evaporation process. A UV-active cargo is used as a drug model to investigate the release behavior of the lignin nanocarriers depending on their morphology. To prove the enzymatic response of the lignin nanocarriers, we tested the enzyme laccase as a trigger to release the encapsulated cargo. Furthermore, porous lignin nanoparticles with high surface area were produced by carbonization. The carbon material has a high potential as an adsorbent, which was studied by adsorption tests with methylene blue. These biodegradable nanocarriers based on the polyfunctional bioresource lignin may find useful application as novel drug delivery vehicle in agriculture or as carbon materials for water purification.

Lignin for Nano‐ and Microscaled Carrier Systems: Applications, Trends, and Challenges

“…Consequently, such enzyme‐responsive nanocarriers were proposed for agricultural applications. The same group later described solid, porous, and core–shell microparticulate systems prepared from methacrylated KL by radical‐initiated emulsion polymerization . The morphology of the capsules depended on the proportion of dispersed hydrophobic phase in the emulsion.…”

“…In this process, solvent is vaporized from a solution of lignin, forming particles at the hydrophobic solvent–air interface. Emulsion templates represent a common approach to the synthesis of lignin nano‐ and microcapsuIes (Figure f) . In addition, synthesis of lignin nanotubes was conducted using sacrificial aluminum templates …”

“…(f) Synthesis of nanoparticles, nanocapsules, and porous microparticles by emulsion‐phase polymerization and cross‐linking (adapted with permission from Refs. Copyright (2016, 2017) American Chemical Society).…”

Future manufacturing and remanufacturing of polymeric materials

“…Nanoencapsulation via miniemulsion polymerization or other processes, provides opportunities for exceptional reinforcement and property improvement, as well as enhanced barrier properties . In addition, nanocapsules can be used as carriers for therapeutics, hollow particles for improved optical properties, and smart polymers capable of responding to environmental stimuli . A similar but very different application is that of highly branched (almost dendritic) poly (n‐isopropyl acrylamide) (NIPAM).…”

Self‐assembly of a renewable lignin biopolymer in nanoparticles with multiple morphologies

“…However, it has been estimated that only about 5–10% of lignin is fully used as value‐added products, such as concrete fillers, dispersants, and additives; the rest has been burned as industrial waste . Recently, efforts have been made to explore the use of lignin as an excipient of macrodrug or nanodrug carriers for the encapsulation, protection, and controlled release of drugs …”