pH-responsive hydrogels based on polyethylene glycol and modified kraft lignin for drug delivery

Introduction: In recent years, hydrogels have gained significant importance in the pharmaceutical industry as an alternative system for controlled drug delivery. Conventional administration methods often fail to maintain optimal therapeutic concentrations, limiting drug action at the target site. Owing to their versatility and biocompatibility, hydrogels offer significant advantages by enabling the incorporation of active molecules and supporting a wide range of biomedical applications. Materials and methods: In this study, kraft lignin and polyethylene glycol were chemically modified via nucleophilic substitution reactions to introduce vinyl groups and were characterized using different spectroscopical techniques to ensure the success of the synthesis. These substances were subsequently used as crosslinking agents and comonomers for the synthesis of hydrogels, using acrylic acid as the monomer. The hydrogels were tested as potential materials for the release of trimethoprim based on preliminary studies. Results: The resulting hydrogels were characterized by evaluating their swelling behavior in water and buffer solutions at pH 4, 7, and 10, revealing a pronounced pH-sensitive response. Additionally, the adsorption and release behavior of the drug trimethoprim from polymeric hydrogel matrices was studied using Ultraviolet – Visible (UV–Vis) spectroscopy. The swelling analyses confirmed that the hydrogels provide tunable diffusion properties suitable for controlled drug delivery applications. Conclusions: The results demonstrate that modified kraft lignin and polyethylene glycol hydrogels possess favorable physicochemical and drug release properties, highlighting their potential as effective controlled-release systems for pH-sensitive drugs in pharmaceutical applications.