title: Improved antibacterial phototoxicity of a neutral porphyrin in natural deep eutectic solvents.
abstract: Neutral porphyrins for antibacterial photodynamic therapy (aPDT) have received little attention due to their tendency to aggregate in aqueous media and reports of low phototoxic effect. These compounds may be less toxic to cells than positively and negatively charged photosensitisers. The preparation of highly bacterial phototoxic formulations of neutral porphyrins remains an open field of research with great potential if achievable. The purpose of this study was to develop novel hydrophilic formulations of the neutral porphyrin 5,10,15,20-tetrakis(4-hydroxyphenyl)-porphyrin (THPP) by use of natural deep eutectic solvents (NADES) prepared by the solvent evaporation method. Physical and photochemical stability and in vitro photoinactivation of Enterococcus faecalis and Escherichia coli were investigated. Two of the 15 NADES investigated demonstrated superior solubilising properties of THPP. The photostability of THPP was higher in NADES than in methanol. A 100-fold dilution of the preparations with buffer to a final concentration of 0.5-5 nM THPP resulted in complete photoinactivation of E. faecalis and E. coli both in their exponential and stationary phase. THPP demonstrated significantly higher phototoxicity when formulated in NADES than in other aqueous preparations like phosphate buffered saline. NADES as a formulation concept for photosensitisers shows a great potential in aPDT.
authors.affiliation: Department of Pharmacy, School of Pharmacy, University of Oslo, P.O. Box 1068 Blindern, 0316 Oslo, Norway. Electronic address: k.o.wikene@farmasi.uio.no.
authors.forename: Kristine Opsvik
authors.initials: KO
authors.lastname: Wikene
authors.affiliation: Nordic Institute of Dental Materials AS, Sognsveien 70A, 0855 Oslo, Norway. Electronic address: ellen.bruzell@niom.no.
authors.forename: Ellen
authors.initials: E
authors.lastname: Bruzell
authors.affiliation: Department of Pharmacy, School of Pharmacy, University of Oslo, P.O. Box 1068 Blindern, 0316 Oslo, Norway. Electronic address: h.h.tonnesen@farmasi.uio.no.
authors.forename: Hanne Hjorth
authors.initials: HH
authors.lastname: Tønnesen
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D013293:Enterococcus faecalis / Q000187:drug effects / Q000528:radiation effects; D004926:Escherichia coli / Q000187:drug effects / Q000528:radiation effects; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D017319:Photosensitizing Agents / Q000737:chemistry / Q000633:toxicity; D011427:Propiophenones / Q000737:chemistry* / Q000633:toxicity; D012995:Solubility; D012997:Solvents / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D017319:Photosensitizing Agents; D011427:Propiophenones; D012997:Solvents; C014870:flopropione