Tuning the local solvent composition at a drug carrier surface: the effect of dimethyl sulfoxide/water mixture on the photofunctional properties of hypericin-β-lactoglobulin complexes

P. Delcanale, B. Rodríguez-Amigo, J. Juárez-Jiménez, F Javier Luque, Stefania Abbruzzetti, M. Agut, Santi Nonell, Cristiano Viappiani

Research output: Contribution to journalArticlepeer-review

Abstract

Aggregation is a major problem for the anti-microbial photodynamic applications of hydrophobic photosensitizers since it strongly reduces the amount of singlet oxygen generated in aqueous solutions. Binding of hypericin (Hyp) to the milk whey protein β-lactoglobulin (βLG), occurring at the two hydrophobic cavities located at the interface of the protein homodimer, can be exploited to confer water-solubility and biocompatibility to the photosensitizer. The introduction of a small amount of the organic cosolvent dimethyl sulfoxide (DMSO) leads to a remarkable improvement of the photophysical properties of the complex Hyp-βLG by increasing its fluorescence emission and singlet oxygen photosensitization quantum yields. Surprisingly, the ability of the complex to photo-inactivate bacteria of the strain Staphylococcus aureus is strongly reduced in the presence of DMSO, despite the higher yield of photosensitization. The reasons for this apparently contradictory behavior are investigated, providing new insights into the use of carrier systems for hydrophobic photosensitizers.

Original languageEnglish
Pages (from-to)1633-1641
Number of pages9
JournalJournal of Materials Chemistry B: Materials for biology and medicine
Volume5
Issue number8
Early online date20 Jan 2017
DOIs
Publication statusE-pub ahead of print - 20 Jan 2017

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