Rose Bengal-Incorporated Supramolecular Gels as a Topical Platform for Localized Antimicrobial Photodynamic Therapy

Efficient and localized singlet oxygen (SO) generation is essential for improving antimicrobial photodynamic therapy (aPDT). In this study, a bis-imidazolium-based amphiphilic gelator is used, which self-assembles into a supramolecular gel in a water-ethanol medium and incorporates Rose Bengal (<b>RB</b>) as a photosensitizer. The gel network provides a confined environment that promotes SO formation under light irradiation. <b>RB</b>@Gel was characterized with respect to its morphology, degradation behavior, and swelling properties. Biopharmaceutical assessment included in vitro release, ex vivo permeation studies and Hen's Egg Test-Chorioallantoic Membrane (HET-CAM) assay. Rheological measurements confirmed a viscoelastic profile, indicating structural stability and suitability for localized therapeutic applications. SO production within the gel was quantified using tetrasodium 9,10-anthracenediyl-bis(methylene)dimalonate (NaABMA), showing higher efficiency than that of <b>RB</b> in solution. The <b>RB</b>@Gel exhibited significant aPDT against <i>E. coli</i> in a direct-surface contact assay. Overall, the <b>RB</b>@Gel provides a stable, suitable platform capable of efficient SO generation and potent antibacterial activity, highlighting its promise for localized aPDT applications.