Captisol/porphyrin nanocomplexes with potential in PAT

The importance of nanomaterials for science and technology has highly increased in the last year paving the way to the development of novel and smart formulations to overcome the limitations of organic chromophores, and significantly accelerate their clinical translation. Cyclodextrins (CDs) improve the biocompatibility of nanodelivery systems, and therefore their use, exploiting a supramolecular approach, can improve the design and applications of functional delivery systems. Aim of this work was to design a novel photosensitizing nanosystem based on CAPTISOL® (sulphobutylether-beta-cyclodextrin, SBE-beta-CD) with the tetracationic water soluble meso-tetrakis(N-methylpyridinium- 4-yl)porphine (TMpyP), as photosensitizer, for photodynamic antimicrobial therapy (PAT) able to promote internalization in cell/bacterial with biocompatible nanoformulations. PAT mechanism involves a photosensitizer (PS), bound to the colonized surface, which is promoted to its excited singlet state (1PS) by shining light on its absorption bands. This species evolves to the triplet state (3PS) that can decay by transferring energy to the surrounding oxygen and molecular components. These systems were studied with complementary techniques such as UV-Vis, steady-state and time resolved fluorescence spectroscopy and characterized to elucidate size and z-potential. The stoichiometry and the stability constant of the CAPTISOL®/TMpyP complex were calculated with the continuous variation method (Job's plot).