# 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.

## Key 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.