Lignosulfonate Microcapsules for Delivery and Controlled Release of Thymol and Derivatives

Abstract

Thymol and the corresponding brominated derivatives constitute important biological active molecules as antibacterial, antioxidant, antifungal, and antiparasitic agents. However, their application is often limited, because their pronounced fragrance, their poor solubility in water, and their high volatility. The encapsulation of different thymol derivatives into biocompatible lignin-microcapsules is presented as a synergy-delivering remedy. The adoption of lignosulfonate as an encapsulating material possessing relevant antioxidant activity, as well as general biocompatibility allows for the development of new materials that are suitable for the application in various fields, especially cosmesis. To this purpose, lignin microcapsules containing thymol, 4-bromothymol, 2,4-dibromothymol, and the corresponding O-methylated derivatives have been efficiently prepared through a sustainable ultrasonication procedure. Actives could be efficiently encapsulated with efficiencies of up to 50%. To evaluate the applicability of such systems for topical purposes, controlled release experiments have been performed in acetate buffer at pH 5.4, to simulate skin pH: all of the capsules show a slow release of actives, which is strongly determined by their inherent lipophilicity.

Thymol and Thyme Essential Oil—New Insights into Selected Therapeutic Applications

“…The research group led by Piombino [ 79 ] has shown that it is also possible to encapsulate thymol and its derivatives into microcapsules made of natural polymers. Good biocompatibility with thymol is shown by lignin derivatives, especially lignosulfonate.…”

Sustainable Strategies in the Synthesis of Lignin Nanoparticles for the Release of Active Compounds: A Comparison

“…[5] The struggle in the development of processes to break lignin into small molecules of well-defined composition relies on its complex and not unique structure, which strongly depends on the type of plant and on the technology employed for its isolation. [6,7] Besides the conversion of lignin into platform chemicals and fuel, an alternative exploitation strategy is the transformation into micro-or nano-structures [8] such as particles, [9,10] capsules, [11][12][13] or fibers. [14,15] Lignin nanoparticles (LNPs) have been produced following various protocols and used for a wide range of applications, such as fillers in nanocomposites to enhance the mechanical properties of the polymeric matrix [17] or to confer UV-blocking properties, [18] biocides, [19] antioxidants/radical scavengers, [20] and drug carriers.…”

“…[21] Among these possible exploitation strategies, also due to lignin biocompatibility, LNPs guaranteed excellent results when used for drug delivery purposes. [8,11,22,23] Solvent-antisolvent is one of the most common methods for the preparation of LNPs: solvent shifting by addition of a nonsolvent into a lignin solution, or vice versa, causes the formation of spherical particles due to the minimization of surface energy. [8,24] Several solvent mixtures have been employed to solubilize lignin, while water is the most frequent anti-solvent.…”

“…The struggle in the development of processes to break lignin into small molecules of well‐defined composition relies on its complex and not unique structure, which strongly depends on the type of plant and on the technology employed for its isolation . Besides the conversion of lignin into platform chemicals and fuel, an alternative exploitation strategy is the transformation into micro‐ or nano‐structures such as particles, capsules, or fibers …”

“…Lignin nanoparticles (LNPs) have been produced following various protocols and used for a wide range of applications, such as fillers in nanocomposites to enhance the mechanical properties of the polymeric matrix or to confer UV‐blocking properties, biocides, antioxidants/radical scavengers, and drug carriers . Among these possible exploitation strategies, also due to lignin biocompatibility, LNPs guaranteed excellent results when used for drug delivery purposes …”