Valorization of Plant Biomass Through the Synthesis of Lignin-Based Hydrogels for Drug Delivery

TL;DR

This paper explores using orange tree pruning waste to create lignin-based hydrogels that can deliver drugs like ibuprofen effectively.

Contribution

The study introduces a novel method to synthesize lignin-based hydrogels from orange tree residues for drug delivery.

Findings

Lignin extracted from orange tree residues showed characteristic functional groups and monolignols via FTIR analysis.

Hydrogels encapsulated ibuprofen and released about 87% of it within 5 hours in a simulated environment.

The Korsmeyer–Peppas model accurately predicted the drug and lignin release rates.

Abstract

This study focuses on obtaining lignin-based hydrogels from pruning residues of orange trees in the Safor region (Valencia) using an alkaline extraction method. The structural analysis of the obtained lignin was carried out using Fourier-transform infrared spectroscopy (FTIR), which revealed the characteristic functional groups of lignin, as well as its structural monolignols: syringyl and guaiacyl. The thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis. The DSC thermogram revealed a relatively low glass transition temperature (Tg) of 67 °C, which may be attributed to partial lignin chain degradation during alkaline extraction. Soda lignin was obtained at 190 °C with an approximate yield of 10.8% relative to the initial biomass and subsequently used to synthesize poly(vinyl alcohol) (PVA)-based hydrogels for ibuprofen encapsulation. Finally, the release experiments of the encapsulated ibuprofen were carried out in an aqueous phosphate buffer medium (pH = 7) at room temperature. A multi-curve response analysis (MCR) algorithm using the Korsmeyer–Peppas (KP) concentration model was used to analyze the release curves, which concluded that the drug and water-soluble lignin fraction (SLF) were released at different rates. For both components, a good correlation was obtained between the measured responses and those provided by the KP model. The release profile indicated that approximately 87% of the initial ibuprofen load was released from the hydrogel within 5 h, highlighting the promising potential of lignin-based hydrogels for drug delivery applications.

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