Preparation of Nanocapsules via the Self-Assembly of Kraft Lignin: A Totally Green Process with Renewable Resources

Abstract

Kraft lignin (KL), the byproduct from the alkali pulping process in the paper industry, is an abundant renewable resource. It was found that KL could be used to form nanocapsules via self-assembly induced by adding water to an ethanol solution of KL. From the results of various imaging techniques and laser light scattering techniques, the hollow sphere feature of this product was confirmed. It was found that there is a higher percentage of ethanol enriched in the interior of the nanocapsules and that the different KL fractions can be spontaneously distributed in the shells according to their hydrophilic–lipophilic sequence. The π–π interactions between the aromatic rings are considered to be an important driving force in the assembly process of the KL nanocapsules. Moreover, the sizes of these KL nanocapsules can vary in the range of tens to hundreds of nanometers, depending on the preparation conditions, which enhance their flexibility to adapt to the potential applications in various fields. Preparation of KL nanocapsules requires only a simple mix of KL/ethanol solution and water, which is a totally green process utilizing a renewable resource.

Lignin for polymer and nanoparticle production: Current status and challenges

“…Nanoparticles are then filtered from the system. When the solvent environment is changed in the mixture, nanoparticles are formed via self‐assembly of lignin molecules driven by forming van der Waals and π‐π interactions between the aromatic rings of lignin . Table summarizes the specifications of lignin‐based nanoparticles produced from different sources.…”

“…Spherical LNPs were generated by dissolving softwood KL in THF and subsequently introducing water into the system through dialysis, which made nanoparticles with better dispersion performance compared with that generated via dropping method . KL based nanoparticles were generated via adding water to an ethanol solution containing KL …”

“…The properties of LNP depend on lignin type and preparation conditions . For the same lignin type, different production methods yielded LNPs with different sizes, shapes, and stability in water.…”

“…Ge et al also fabricated LNPs of lignosulphonates following these two alternative methods, which yielded LNPs with varied particle sizes. Li et al reported that spherical and hollow LNPs were obtained by using dioxane and ethanol as solvents in the solvent shifting precipitation of KL. Following the same method of solvent shifting, spherical and irregular shaped nanoparticles were produced by using OSL and KL, respectively …”

“…LNPs have been fabricated from soda lignin with favourable uniformity and spherical shape for drug delivery . In addition, hollow shaped LNPs can be potentially used as polymer nanocapsules that have a liquid core and a polymeric shell to encapsulate a variety of guest molecules for drug delivery and release . Chen et al produced a LNP drug carrier with a load capacity of 37.4 wt% of tested drug on LNP and sustained drug‐releasing capability and biocompatibility in the in vitro and in vivo tests.…”