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 (RB) as a photosensitizer. The gel network provides a confined environment that promotes SO formation under light irradiation. RB@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 RB in solution. The RB@Gel exhibited significant aPDT against E. coli in a direct-surface contact assay. Overall, the RB@Gel provides a stable, suitable platform capable of efficient SO generation and potent antibacterial activity, highlighting its promise for localized aPDT applications.