Antimicrobial NIR-Responsive Hydrogels Based on Gellan Gum and Bis-MPA Polyester Dendrimers

In this study, a near-infrared (NIR)-responsive hydrogel based on ethylenediamine (EDA)-functionalized Gellan Gum was developed through a simple preparation method. This hydrogel incorporates in situ synthesized polydopamine (pDA) and was loaded with first- and second-generation antimicrobial bis-MPA polyester dendrimers (TMP-G1-[Cys]₆ and MP-G2-[Cys]₁₂), bearing cysteamine hydrochloride as peripheral functional groups. The intrinsic ability of pDA to scavenge reactive oxygen species (ROS) and convert NIR light at 810 nm into heat imparted radical scavenging activity and photothermal properties to the systems. It has been demonstrated that, due to the noncovalent interactions with both GG-EDA and pDA, dendrimers are retained differently within the sample depending on their molecular weight and the number of terminal positive charges. This difference in retention influences their antimicrobial activity against <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i>. In particular, it has been shown that the NIR-induced photothermal effect plays a crucial role in triggering the activity of the sample loaded with the most retained dendrimer, which possesses the highest number of terminal positive charges. The high physiological fluid absorption capacity makes these materials ideal for wound exudate management. In addition, their resistance to hydrolytic degradation can be exploited to reduce the frequency of dressing changes, potentially improving patient comfort. The dendrimer-loaded samples demonstrated low cytotoxicity toward human fetal dermal mesenchymal stromal cells (FD-MSCs) and human epidermal keratinocytes (HaCaT). These findings suggest that GG-EDA@pDA+TMP-G1-[Cys]₆ or TMP-G2-[Cys]₁₂ could be promising candidates for the treatment of infected skin wounds.