Nanocomplexes based on a cationic porphyrin and an anionic cyclodextrin with antimicrobial photodynamic properties

Nowadays, novel less-expensive nanoformulations for in situ-controlled and safe delivery of photosensitiser (PS) against opportunistic pathogens in body-infections areas needs to be developed. Following our ongoing research on nanophototerapeutics [1-3], here we propose the design and characterization of a novel photosensitizing nanosystem based on the marketed cyclodextrin CAPTISOL® (sulphobutylether-beta-cyclodextrin, SBE-beta-CD) to fabricate efficient biocompatible systems for antimicrobial photodynamic therapy (aPDT). Firstly, interaction studies were carried out in order to investigate the complexation between CAPTISOL® with the tetracationic water soluble meso-tetrakis(N-methylpyridinium- 4-yl)porphine (TMPyP). Nanocomplexes based on CAPTISOL® and TMPyP ( NanophotoCapitsol) were prepared in aqueous media and characterized by complementary spectroscopy and microscopic tecniques such as UV/vis, fluorescence spectroscopy, atomic force microscopy ( AFM) and scanning-near field optical luminescence (SNOL), thus investigating complex stoichiometry, stability constant, photophysical and morphological properties. Furthermore size and ?-potential were measured by Dynamic light scattering and Electrophoretic Light Scattering, respectively. Release and stability studies were performed in physiological conditions pointed out the role of CAPTISOL® to sustain the PS release. Finally, photoantimicrobial activity of the NanophotoCapitisol vs free porphyrin were investigated against Gram-negative Pseudomonas aeruginosa ATCC 27853, by showing as the proposed nanosystems can control along the time the release of porphyrin to photokill Gram-negative bacterial cells.