Hypericin Loaded Liposomes for Anti-Microbial Photodynamic Therapy of Gram-Positive Bacteria

Due to its highly lipophilic nature, poor solubility in aqueous media, and poor bioavailability, the naturally occurring photosensitizer hypericin has a limited therapeutic value. Liposomal encapsulation is a promising solution to overcome these limitations. Use of liposomes as delivery vehicles for hypericin in antimicrobial photodynamic therapy (aPDT) is quite new. The aim of this work is therefore, to prepare various hypericin loaded liposomal formulations viz. DOPE/CHEMS/DPPC, DSPC/DPPC/DSPE-PEG, and DPPC/DOTAP. The formulations are physicochemically characterized and tested for their binding affinity toward bacteria and for their photodynamic efficiency. All formulations achieve a 2.3-2.5 log reduction of Staphylococcus saprophyticus subsp. bovis and facilitate the binding and uptake of the photosensitizer through the bacterial cell wall.