Hybrid Pectin/Polydopamine Hydrogels with Photothermal Properties

Photothermal hydrogels have emerged as versatile materials for applications in biomedicine, environmental remediation, and soft robotics due to their ability to convert light energy into heat. In this study, we developed hybrid pectin/polydopamine (PDA) hydrogels with intrinsic photothermal properties through a simple, scalable approach. Pectin, a naturally occurring and biodegradable polysaccharide, was functionalized with PDA via dopamine self-polymerization under alkaline conditions, followed by Ca²⁺-induced cross-linking to form a hydrogel network. The structural and chemical interactions between pectin and PDA were analyzed by using FTIR and UV-vis spectroscopy, confirming successful functionalization and formation of a hybrid structure. The mechanical and viscoelastic properties of the hydrogels were investigated, revealing that PDA acts as a secondary cross-linker with pectin due to its ability to form hydrogen bonds and π-π interactions, resulting in a more flexible but mechanically weaker cross-linked network. SEM and swelling ratio analysis demonstrated that PDA incorporation resulted in a denser hydrogel network compared with neat pectin hydrogels while retaining their swelling behavior. DSC analyses supported this trend, indicating microstructural disruption and reduced thermal stability at higher PDA levels. The photothermal performance of the pectin/PDA hydrogels was assessed under 808 nm near-infrared (NIR) laser irradiation, showing a significant temperature elevation proportional to PDA content. Furthermore, light-activated antibacterial tests using Staphylococcus aureus confirmed that NIR-triggered heating effectively reduced bacterial viability, achieving a 3-log reduction in the bacterial count for the highest PDA concentration. These findings demonstrate that pectin has been successfully transformed into a photothermal hydrogel matrix through a simple approach and highlight the potential of pectin/PDA hydrogels as biocompatible, light-responsive materials.